Re: GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Pavel Machek]

On Fri 2017-01-20 18:16:11, Andy Shevchenko wrote:
> On Fri, 2017-01-20 at 16:26 +0100, Linus Walleij wrote:
> 
> > > Now, NMEA knows about some of the complexity (not AGPS), but gets
> > > the
> > > details wrong. In particular, it would be good to have error
> > > estimates
> > > and velocities from the same moment you get position estimates.
> > 
> > NMEA if it is this:
> > https://en.wikipedia.org/wiki/NMEA_0183
> > 
> > Seems to be a high-level format such as XML or CSV or any other
> > $FAVOURITE_ASCII_TRANSPORT format.
> 
> Not exactly. It depends on device settings.
> Old GPS I used to play with have AT command to switch between ASCII and
> binary format. Some of the devices might use non-standard binary
> protocols (however, representable as NMEA), etc.

Apparently NMEA has some serious limitations. gpsd authors have some
good docs about that.
Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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Re: GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Pavel Machek]

On Fri 2017-01-20 18:16:11, Andy Shevchenko wrote:
> On Fri, 2017-01-20 at 16:26 +0100, Linus Walleij wrote:
> 
> > > Now, NMEA knows about some of the complexity (not AGPS), but gets
> > > the
> > > details wrong. In particular, it would be good to have error
> > > estimates
> > > and velocities from the same moment you get position estimates.
> > 
> > NMEA if it is this:
> > https://en.wikipedia.org/wiki/NMEA_0183
> > 
> > Seems to be a high-level format such as XML or CSV or any other
> > $FAVOURITE_ASCII_TRANSPORT format.
> 
> Not exactly. It depends on device settings.
> Old GPS I used to play with have AT command to switch between ASCII and
> binary format. Some of the devices might use non-standard binary
> protocols (however, representable as NMEA), etc.

Apparently NMEA has some serious limitations. gpsd authors have some
good docs about that.
Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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Re: GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Pavel Machek]

Hi!

> >> In my simple opinion GPSes shound live in drivers/iio/gps simply by
> >> usecase association: streaming out a series of accelerometer readings
> >> periodically through IIOs chardevs and other data about the physical
> >> world is not any different from the GPS usecase that give you a stream
> >> of coordinates on where on this planet you are.
> >
> > That is... not quite how GPSes work. What interface would you propose?
> > It would be good to support error estimates in position/velocities and
> > AGPS data upload.
> 
> Sorry for my ignorance. I have not had the opportunity to work
> directly with a GPS hardware.

Few people have. It is CDMA corelators at the low level. 

> > Now, NMEA knows about some of the complexity (not AGPS), but gets the
> > details wrong. In particular, it would be good to have error estimates
> > and velocities from the same moment you get position estimates.
> 
> NMEA if it is this:
> https://en.wikipedia.org/wiki/NMEA_0183

Yes.

> Seems to be a high-level format such as XML or CSV or any other
> $FAVOURITE_ASCII_TRANSPORT format.
> 
> What we want to push into the ring buffer is of course the raw data
> that is produced by the GPS hardware, whatever that may be.
> If what we have is this text format we should not reverse-translate
> it back any more than modem AT commands, it doesn't make sense
> I guess.

Umm. Its hairy. Each GPS talks slightly different version of NMEA
:-(. But yes, we have userland driver called 'gpsd' that understands
most of them. Many GPSes have additional, non-NMEA protocol you can
switch them to.

> So NMEA processing would be in userspace. And if the GPS is just
> streaming this text data over to the client, like Marcel says, it is
> more reasonable to just feed that up to userspace (no policy in the
> kernel).

Well -- we normally do hardware abstraction in the kernel :-).

> I am however aware of certain hardware such as the ST
> Microelectronis STA2062 produced for Garmin, which is *not*
> connected to any external chip, and is not talking over serial
> to any RSx port, and does not have an embedded firmware running
> on another SoC in any special GPS chip. And it is unassisted.

I googled STA2062 but it does not make much sense to me.

Yes, not everything talks NMEA. Nokia N900 is an example, and it has
in-tree driver.

> Maybe that is an oddity. In the mobile phone business I guess it
> could be more common to have a separate SoC that by way
> of standards just stream NMEA data.

Sorry, I don't understand. Yes, in mobile phones GPSes that produce
something else than NMEA are pretty common.

> Fusing that with other sensor data (accelerometer, compass, etc)
> is again indeed a userspace task. I hope NMEA includes very good
> timestamps.

Umm. Timestamps are quite hard to do over serial :-(.
Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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Re: GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Pavel Machek]

Hi!

> >> In my simple opinion GPSes shound live in drivers/iio/gps simply by
> >> usecase association: streaming out a series of accelerometer readings
> >> periodically through IIOs chardevs and other data about the physical
> >> world is not any different from the GPS usecase that give you a stream
> >> of coordinates on where on this planet you are.
> >
> > That is... not quite how GPSes work. What interface would you propose?
> > It would be good to support error estimates in position/velocities and
> > AGPS data upload.
> 
> Sorry for my ignorance. I have not had the opportunity to work
> directly with a GPS hardware.

Few people have. It is CDMA corelators at the low level. 

> > Now, NMEA knows about some of the complexity (not AGPS), but gets the
> > details wrong. In particular, it would be good to have error estimates
> > and velocities from the same moment you get position estimates.
> 
> NMEA if it is this:
> https://en.wikipedia.org/wiki/NMEA_0183

Yes.

> Seems to be a high-level format such as XML or CSV or any other
> $FAVOURITE_ASCII_TRANSPORT format.
> 
> What we want to push into the ring buffer is of course the raw data
> that is produced by the GPS hardware, whatever that may be.
> If what we have is this text format we should not reverse-translate
> it back any more than modem AT commands, it doesn't make sense
> I guess.

Umm. Its hairy. Each GPS talks slightly different version of NMEA
:-(. But yes, we have userland driver called 'gpsd' that understands
most of them. Many GPSes have additional, non-NMEA protocol you can
switch them to.

> So NMEA processing would be in userspace. And if the GPS is just
> streaming this text data over to the client, like Marcel says, it is
> more reasonable to just feed that up to userspace (no policy in the
> kernel).

Well -- we normally do hardware abstraction in the kernel :-).

> I am however aware of certain hardware such as the ST
> Microelectronis STA2062 produced for Garmin, which is *not*
> connected to any external chip, and is not talking over serial
> to any RSx port, and does not have an embedded firmware running
> on another SoC in any special GPS chip. And it is unassisted.

I googled STA2062 but it does not make much sense to me.

Yes, not everything talks NMEA. Nokia N900 is an example, and it has
in-tree driver.

> Maybe that is an oddity. In the mobile phone business I guess it
> could be more common to have a separate SoC that by way
> of standards just stream NMEA data.

Sorry, I don't understand. Yes, in mobile phones GPSes that produce
something else than NMEA are pretty common.

> Fusing that with other sensor data (accelerometer, compass, etc)
> is again indeed a userspace task. I hope NMEA includes very good
> timestamps.

Umm. Timestamps are quite hard to do over serial :-(.
Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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Re: GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Andy Shevchenko]

On Fri, 2017-01-20 at 16:26 +0100, Linus Walleij wrote:

> > Now, NMEA knows about some of the complexity (not AGPS), but gets
> > the
> > details wrong. In particular, it would be good to have error
> > estimates
> > and velocities from the same moment you get position estimates.
> 
> NMEA if it is this:
> https://en.wikipedia.org/wiki/NMEA_0183
> 
> Seems to be a high-level format such as XML or CSV or any other
> $FAVOURITE_ASCII_TRANSPORT format.

Not exactly. It depends on device settings.
Old GPS I used to play with have AT command to switch between ASCII and
binary format. Some of the devices might use non-standard binary
protocols (however, representable as NMEA), etc.

-- 
Andy Shevchenko 
Intel Finland Oy

Re: GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Andy Shevchenko]

On Fri, 2017-01-20 at 16:26 +0100, Linus Walleij wrote:

> > Now, NMEA knows about some of the complexity (not AGPS), but gets
> > the
> > details wrong. In particular, it would be good to have error
> > estimates
> > and velocities from the same moment you get position estimates.
> 
> NMEA if it is this:
> https://en.wikipedia.org/wiki/NMEA_0183
> 
> Seems to be a high-level format such as XML or CSV or any other
> $FAVOURITE_ASCII_TRANSPORT format.

Not exactly. It depends on device settings.
Old GPS I used to play with have AT command to switch between ASCII and
binary format. Some of the devices might use non-standard binary
protocols (however, representable as NMEA), etc.

-- 
Andy Shevchenko 
Intel Finland Oy

Re: GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Linus Walleij]

oOn Fri, Jan 20, 2017 at 3:22 PM, Pavel Machek  wrote:

> Switched subject: Rob's work is great for GPS and bluetooth, but this
> goes beyond it.

Sure why not talk around a bit.

>> In my simple opinion GPSes shound live in drivers/iio/gps simply by
>> usecase association: streaming out a series of accelerometer readings
>> periodically through IIOs chardevs and other data about the physical
>> world is not any different from the GPS usecase that give you a stream
>> of coordinates on where on this planet you are.
>
> That is... not quite how GPSes work. What interface would you propose?
> It would be good to support error estimates in position/velocities and
> AGPS data upload.

Sorry for my ignorance. I have not had the opportunity to work
directly with a GPS hardware.

> Now, NMEA knows about some of the complexity (not AGPS), but gets the
> details wrong. In particular, it would be good to have error estimates
> and velocities from the same moment you get position estimates.

NMEA if it is this:
https://en.wikipedia.org/wiki/NMEA_0183

Seems to be a high-level format such as XML or CSV or any other
$FAVOURITE_ASCII_TRANSPORT format.

What we want to push into the ring buffer is of course the raw data
that is produced by the GPS hardware, whatever that may be.
If what we have is this text format we should not reverse-translate
it back any more than modem AT commands, it doesn't make sense
I guess.

So NMEA processing would be in userspace. And if the GPS is just
streaming this text data over to the client, like Marcel says, it is
more reasonable to just feed that up to userspace (no policy in the
kernel).

I am however aware of certain hardware such as the ST
Microelectronis STA2062 produced for Garmin, which is *not*
connected to any external chip, and is not talking over serial
to any RSx port, and does not have an embedded firmware running
on another SoC in any special GPS chip. And it is unassisted.

Maybe that is an oddity. In the mobile phone business I guess it
could be more common to have a separate SoC that by way
of standards just stream NMEA data.

Fusing that with other sensor data (accelerometer, compass, etc)
is again indeed a userspace task. I hope NMEA includes very good
timestamps.

Thanks,
Linus Walleij

Re: GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Linus Walleij]

oOn Fri, Jan 20, 2017 at 3:22 PM, Pavel Machek  wrote:

> Switched subject: Rob's work is great for GPS and bluetooth, but this
> goes beyond it.

Sure why not talk around a bit.

>> In my simple opinion GPSes shound live in drivers/iio/gps simply by
>> usecase association: streaming out a series of accelerometer readings
>> periodically through IIOs chardevs and other data about the physical
>> world is not any different from the GPS usecase that give you a stream
>> of coordinates on where on this planet you are.
>
> That is... not quite how GPSes work. What interface would you propose?
> It would be good to support error estimates in position/velocities and
> AGPS data upload.

Sorry for my ignorance. I have not had the opportunity to work
directly with a GPS hardware.

> Now, NMEA knows about some of the complexity (not AGPS), but gets the
> details wrong. In particular, it would be good to have error estimates
> and velocities from the same moment you get position estimates.

NMEA if it is this:
https://en.wikipedia.org/wiki/NMEA_0183

Seems to be a high-level format such as XML or CSV or any other
$FAVOURITE_ASCII_TRANSPORT format.

What we want to push into the ring buffer is of course the raw data
that is produced by the GPS hardware, whatever that may be.
If what we have is this text format we should not reverse-translate
it back any more than modem AT commands, it doesn't make sense
I guess.

So NMEA processing would be in userspace. And if the GPS is just
streaming this text data over to the client, like Marcel says, it is
more reasonable to just feed that up to userspace (no policy in the
kernel).

I am however aware of certain hardware such as the ST
Microelectronis STA2062 produced for Garmin, which is *not*
connected to any external chip, and is not talking over serial
to any RSx port, and does not have an embedded firmware running
on another SoC in any special GPS chip. And it is unassisted.

Maybe that is an oddity. In the mobile phone business I guess it
could be more common to have a separate SoC that by way
of standards just stream NMEA data.

Fusing that with other sensor data (accelerometer, compass, etc)
is again indeed a userspace task. I hope NMEA includes very good
timestamps.

Thanks,
Linus Walleij

Re: [PATCH v2 0/9] Serial slave device bus

[H. Nikolaus Schaller]

> Am 20.01.2017 um 15:14 schrieb Marcel Holtmann :
> 
> Hi Linus,
> 
>>> There's still some discussion about what to do with devices that pass thru
>>> data to userspace unmodified like GPS and could still use tty device for
>>> the data path. IMO, we should treat this as a separate problem following
>>> this series. Drivers we want to convert to serdev and already in the
>>> kernel don't need this functionality.
>> 
>> In my simple opinion GPSes shound live in drivers/iio/gps simply by
>> usecase association: streaming out a series of accelerometer readings
>> periodically through IIOs chardevs and other data about the physical
>> world is not any different from the GPS usecase that give you a stream
>> of coordinates on where on this planet you are.
>> 
>> The fact that vendors like to defer GPS processing to userspace because
>> it is considered "secret sauce" is not the concern of the kernel community,
>> though problems like that in general is the great tragedy of our time.
>> 
>> It would be fun to see a pure, reverse-engineered GPS driver in IIO.
> 
> except for the pure NMEA devices. Which are pretty much defined as terminal 
> devices using RS422 and 4800 baud. For anything non-NMEA, I would agree that 
> using IIO might be a good option. So instead of a GPS subsystem, might just 
> have a GPS class / type in the IIO subsystem.

Well, we could implement a default NMEA parser in the iio subsystem to
translate satellite time, geolocation, orientation, speed, and satellite
signal strengths to iio channels.

On the other hand we have to wait until all user-space GPS applications
use it and appear in wider use in distribution. Let's say in 3-4 years?

Therefore, I'd like to see NMEA records passed to user space and not
shielded completely.

And some GPS devices send extensions to the core set of NEMA records,
which might give other useful information. Having this needs some
extensibility to the iio translation or side-channels.

BR,
Nikolaus

Re: [PATCH v2 0/9] Serial slave device bus

[H. Nikolaus Schaller]

> Am 20.01.2017 um 15:14 schrieb Marcel Holtmann :
> 
> Hi Linus,
> 
>>> There's still some discussion about what to do with devices that pass thru
>>> data to userspace unmodified like GPS and could still use tty device for
>>> the data path. IMO, we should treat this as a separate problem following
>>> this series. Drivers we want to convert to serdev and already in the
>>> kernel don't need this functionality.
>> 
>> In my simple opinion GPSes shound live in drivers/iio/gps simply by
>> usecase association: streaming out a series of accelerometer readings
>> periodically through IIOs chardevs and other data about the physical
>> world is not any different from the GPS usecase that give you a stream
>> of coordinates on where on this planet you are.
>> 
>> The fact that vendors like to defer GPS processing to userspace because
>> it is considered "secret sauce" is not the concern of the kernel community,
>> though problems like that in general is the great tragedy of our time.
>> 
>> It would be fun to see a pure, reverse-engineered GPS driver in IIO.
> 
> except for the pure NMEA devices. Which are pretty much defined as terminal 
> devices using RS422 and 4800 baud. For anything non-NMEA, I would agree that 
> using IIO might be a good option. So instead of a GPS subsystem, might just 
> have a GPS class / type in the IIO subsystem.

Well, we could implement a default NMEA parser in the iio subsystem to
translate satellite time, geolocation, orientation, speed, and satellite
signal strengths to iio channels.

On the other hand we have to wait until all user-space GPS applications
use it and appear in wider use in distribution. Let's say in 3-4 years?

Therefore, I'd like to see NMEA records passed to user space and not
shielded completely.

And some GPS devices send extensions to the core set of NEMA records,
which might give other useful information. Having this needs some
extensibility to the iio translation or side-channels.

BR,
Nikolaus

GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Pavel Machek]

Hi!

Switched subject: Rob's work is great for GPS and bluetooth, but this
goes beyond it.

> On Mon, Jan 16, 2017 at 11:54 PM, Rob Herring  wrote:
> 
> > There's still some discussion about what to do with devices that pass thru
> > data to userspace unmodified like GPS and could still use tty device for
> > the data path. IMO, we should treat this as a separate problem following
> > this series. Drivers we want to convert to serdev and already in the
> > kernel don't need this functionality.
> 
> In my simple opinion GPSes shound live in drivers/iio/gps simply by
> usecase association: streaming out a series of accelerometer readings
> periodically through IIOs chardevs and other data about the physical
> world is not any different from the GPS usecase that give you a stream
> of coordinates on where on this planet you are.

That is... not quite how GPSes work. What interface would you propose?
It would be good to support error estimates in position/velocities and
AGPS data upload.

Now, NMEA knows about some of the complexity (not AGPS), but gets the
details wrong. In particular, it would be good to have error estimates
and velocities from the same moment you get position estimates. 

> The fact that vendors like to defer GPS processing to userspace because
> it is considered "secret sauce" is not the concern of the kernel community,
> though problems like that in general is the great tragedy of our time.
> 
> It would be fun to see a pure, reverse-engineered GPS driver in IIO.

Well, many GPSes simply produce NMEA, and we have drivers for some other.

Here's example driver:

https://gitlab.com/tui/tui/blob/master/ofone/gps3.c

Best regards,
Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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GPS drivers (was Re: [PATCH v2 0/9] Serial slave device bus)

[Pavel Machek]

Hi!

Switched subject: Rob's work is great for GPS and bluetooth, but this
goes beyond it.

> On Mon, Jan 16, 2017 at 11:54 PM, Rob Herring  wrote:
> 
> > There's still some discussion about what to do with devices that pass thru
> > data to userspace unmodified like GPS and could still use tty device for
> > the data path. IMO, we should treat this as a separate problem following
> > this series. Drivers we want to convert to serdev and already in the
> > kernel don't need this functionality.
> 
> In my simple opinion GPSes shound live in drivers/iio/gps simply by
> usecase association: streaming out a series of accelerometer readings
> periodically through IIOs chardevs and other data about the physical
> world is not any different from the GPS usecase that give you a stream
> of coordinates on where on this planet you are.

That is... not quite how GPSes work. What interface would you propose?
It would be good to support error estimates in position/velocities and
AGPS data upload.

Now, NMEA knows about some of the complexity (not AGPS), but gets the
details wrong. In particular, it would be good to have error estimates
and velocities from the same moment you get position estimates. 

> The fact that vendors like to defer GPS processing to userspace because
> it is considered "secret sauce" is not the concern of the kernel community,
> though problems like that in general is the great tragedy of our time.
> 
> It would be fun to see a pure, reverse-engineered GPS driver in IIO.

Well, many GPSes simply produce NMEA, and we have drivers for some other.

Here's example driver:

https://gitlab.com/tui/tui/blob/master/ofone/gps3.c

Best regards,
Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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Re: [PATCH v2 0/9] Serial slave device bus

[Marcel Holtmann]

Hi Linus,

>> There's still some discussion about what to do with devices that pass thru
>> data to userspace unmodified like GPS and could still use tty device for
>> the data path. IMO, we should treat this as a separate problem following
>> this series. Drivers we want to convert to serdev and already in the
>> kernel don't need this functionality.
> 
> In my simple opinion GPSes shound live in drivers/iio/gps simply by
> usecase association: streaming out a series of accelerometer readings
> periodically through IIOs chardevs and other data about the physical
> world is not any different from the GPS usecase that give you a stream
> of coordinates on where on this planet you are.
> 
> The fact that vendors like to defer GPS processing to userspace because
> it is considered "secret sauce" is not the concern of the kernel community,
> though problems like that in general is the great tragedy of our time.
> 
> It would be fun to see a pure, reverse-engineered GPS driver in IIO.

except for the pure NMEA devices. Which are pretty much defined as terminal 
devices using RS422 and 4800 baud. For anything non-NMEA, I would agree that 
using IIO might be a good option. So instead of a GPS subsystem, might just 
have a GPS class / type in the IIO subsystem.

Regards

Marcel

Re: [PATCH v2 0/9] Serial slave device bus

[Marcel Holtmann]

Hi Linus,

>> There's still some discussion about what to do with devices that pass thru
>> data to userspace unmodified like GPS and could still use tty device for
>> the data path. IMO, we should treat this as a separate problem following
>> this series. Drivers we want to convert to serdev and already in the
>> kernel don't need this functionality.
> 
> In my simple opinion GPSes shound live in drivers/iio/gps simply by
> usecase association: streaming out a series of accelerometer readings
> periodically through IIOs chardevs and other data about the physical
> world is not any different from the GPS usecase that give you a stream
> of coordinates on where on this planet you are.
> 
> The fact that vendors like to defer GPS processing to userspace because
> it is considered "secret sauce" is not the concern of the kernel community,
> though problems like that in general is the great tragedy of our time.
> 
> It would be fun to see a pure, reverse-engineered GPS driver in IIO.

except for the pure NMEA devices. Which are pretty much defined as terminal 
devices using RS422 and 4800 baud. For anything non-NMEA, I would agree that 
using IIO might be a good option. So instead of a GPS subsystem, might just 
have a GPS class / type in the IIO subsystem.

Regards

Marcel

Re: [PATCH v2 0/9] Serial slave device bus

[Linus Walleij]

On Mon, Jan 16, 2017 at 11:54 PM, Rob Herring  wrote:

> There's still some discussion about what to do with devices that pass thru
> data to userspace unmodified like GPS and could still use tty device for
> the data path. IMO, we should treat this as a separate problem following
> this series. Drivers we want to convert to serdev and already in the
> kernel don't need this functionality.

In my simple opinion GPSes shound live in drivers/iio/gps simply by
usecase association: streaming out a series of accelerometer readings
periodically through IIOs chardevs and other data about the physical
world is not any different from the GPS usecase that give you a stream
of coordinates on where on this planet you are.

The fact that vendors like to defer GPS processing to userspace because
it is considered "secret sauce" is not the concern of the kernel community,
though problems like that in general is the great tragedy of our time.

It would be fun to see a pure, reverse-engineered GPS driver in IIO.

Just my €0.01

(And by the way: awesome work on this series.)

Yours,
Linus Walleij

Re: [PATCH v2 0/9] Serial slave device bus

[Linus Walleij]

On Mon, Jan 16, 2017 at 11:54 PM, Rob Herring  wrote:

> There's still some discussion about what to do with devices that pass thru
> data to userspace unmodified like GPS and could still use tty device for
> the data path. IMO, we should treat this as a separate problem following
> this series. Drivers we want to convert to serdev and already in the
> kernel don't need this functionality.

In my simple opinion GPSes shound live in drivers/iio/gps simply by
usecase association: streaming out a series of accelerometer readings
periodically through IIOs chardevs and other data about the physical
world is not any different from the GPS usecase that give you a stream
of coordinates on where on this planet you are.

The fact that vendors like to defer GPS processing to userspace because
it is considered "secret sauce" is not the concern of the kernel community,
though problems like that in general is the great tragedy of our time.

It would be fun to see a pure, reverse-engineered GPS driver in IIO.

Just my €0.01

(And by the way: awesome work on this series.)

Yours,
Linus Walleij

Re: [PATCH v2 0/9] Serial slave device bus

[Greg Kroah-Hartman]

On Mon, Jan 16, 2017 at 04:54:27PM -0600, Rob Herring wrote:
> Here's a new version of the serdev bus support with all the review
> feedback so far incorporated. I've left it named serdev for now pending
> any further votes one way or the other, but I did rename the sysfs visible
> portions to "serial".
> 
> There's still some discussion about what to do with devices that pass thru
> data to userspace unmodified like GPS and could still use tty device for
> the data path. IMO, we should treat this as a separate problem following
> this series. Drivers we want to convert to serdev and already in the
> kernel don't need this functionality.
> 
> I need a SoB from Alan on his patch 2 and would like review from Alan and/or
> Peter on the locking in patch 5.

I've applied the first 4 patches now, can you respin this and hopefully
Peter will review that patch, as I'd like him to before taking it.

thanks,

greg k-h

Re: [PATCH v2 0/9] Serial slave device bus

[Greg Kroah-Hartman]

On Mon, Jan 16, 2017 at 04:54:27PM -0600, Rob Herring wrote:
> Here's a new version of the serdev bus support with all the review
> feedback so far incorporated. I've left it named serdev for now pending
> any further votes one way or the other, but I did rename the sysfs visible
> portions to "serial".
> 
> There's still some discussion about what to do with devices that pass thru
> data to userspace unmodified like GPS and could still use tty device for
> the data path. IMO, we should treat this as a separate problem following
> this series. Drivers we want to convert to serdev and already in the
> kernel don't need this functionality.
> 
> I need a SoB from Alan on his patch 2 and would like review from Alan and/or
> Peter on the locking in patch 5.

I've applied the first 4 patches now, can you respin this and hopefully
Peter will review that patch, as I'd like him to before taking it.

thanks,

greg k-h

Re: [PATCH v2 0/9] Serial slave device bus

[Sebastian Reichel]

Hi,

On Fri, Jan 20, 2017 at 02:36:12AM +0100, msuchanek wrote:
> On 2017-01-16 23:54, Rob Herring wrote:
> > Here's a new version of the serdev bus support with all the review
> > feedback so far incorporated. I've left it named serdev for now pending
> > any further votes one way or the other, but I did rename the sysfs
> > visible
> > portions to "serial".
> > 
> > There's still some discussion about what to do with devices that pass
> > thru
> > data to userspace unmodified like GPS and could still use tty device for
> > the data path. IMO, we should treat this as a separate problem following
> > this series. Drivers we want to convert to serdev and already in the
> > kernel don't need this functionality.
> 
> The whole point of the serial bus is to simplify and clean up support for
> serial devices.
> If tty users cannot use the kernel support for automagic kill
> switches/resets/whatever with kernel GPIO or whatever framework and must
> continue supporting userspace GPIO and hacks for writing IO space from
> userland for their devices there is just no point.

> I mean it's fine to add support for your single pet device but if you are
> to support non-trivial number of devices they don't get all perfect kernel
> driver overnight. And if you need userspace GPIO for half of your devices
> you can just continue using it for all to *simplify* your userspace code.

This is definitely not about a single pet device. It helps for most
of the serial attached bluetooth chips. For example my work on the
Nokia N-series bluetooth driver is waiting for this series and
supporting the nokia bluetooth chips with userspace GPIOs is more
or less impossible with the data being handled in the kernel, since
GPIOs have to be toggled based on that data.

Also there is the kurobox, which uses a serial attached board reset
controller. It may not need extra GPIOs/regulators/whatever, but it
must have a full-in-kernel driver, so that 'reboot' works as expected ;)

> It has already happened for SPI devices and the implementation of the
> userspace access to SPI is dragging for years.

Talking about dragging for years: This series has been initially
discussed in 2014. Implementing this step-by-step looks sensible
to me.

-- Sebastian


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Re: [PATCH v2 0/9] Serial slave device bus

[Sebastian Reichel]

Hi,

On Fri, Jan 20, 2017 at 02:36:12AM +0100, msuchanek wrote:
> On 2017-01-16 23:54, Rob Herring wrote:
> > Here's a new version of the serdev bus support with all the review
> > feedback so far incorporated. I've left it named serdev for now pending
> > any further votes one way or the other, but I did rename the sysfs
> > visible
> > portions to "serial".
> > 
> > There's still some discussion about what to do with devices that pass
> > thru
> > data to userspace unmodified like GPS and could still use tty device for
> > the data path. IMO, we should treat this as a separate problem following
> > this series. Drivers we want to convert to serdev and already in the
> > kernel don't need this functionality.
> 
> The whole point of the serial bus is to simplify and clean up support for
> serial devices.
> If tty users cannot use the kernel support for automagic kill
> switches/resets/whatever with kernel GPIO or whatever framework and must
> continue supporting userspace GPIO and hacks for writing IO space from
> userland for their devices there is just no point.

> I mean it's fine to add support for your single pet device but if you are
> to support non-trivial number of devices they don't get all perfect kernel
> driver overnight. And if you need userspace GPIO for half of your devices
> you can just continue using it for all to *simplify* your userspace code.

This is definitely not about a single pet device. It helps for most
of the serial attached bluetooth chips. For example my work on the
Nokia N-series bluetooth driver is waiting for this series and
supporting the nokia bluetooth chips with userspace GPIOs is more
or less impossible with the data being handled in the kernel, since
GPIOs have to be toggled based on that data.

Also there is the kurobox, which uses a serial attached board reset
controller. It may not need extra GPIOs/regulators/whatever, but it
must have a full-in-kernel driver, so that 'reboot' works as expected ;)

> It has already happened for SPI devices and the implementation of the
> userspace access to SPI is dragging for years.

Talking about dragging for years: This series has been initially
discussed in 2014. Implementing this step-by-step looks sensible
to me.

-- Sebastian


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Description: PGP signature

Re: [PATCH v2 0/9] Serial slave device bus

[msuchanek]

On 2017-01-16 23:54, Rob Herring wrote:

Here's a new version of the serdev bus support with all the review
feedback so far incorporated. I've left it named serdev for now pending
any further votes one way or the other, but I did rename the sysfs 
visible

portions to "serial".

There's still some discussion about what to do with devices that pass 
thru
data to userspace unmodified like GPS and could still use tty device 
for
the data path. IMO, we should treat this as a separate problem 
following

this series. Drivers we want to convert to serdev and already in the
kernel don't need this functionality.


The whole point of the serial bus is to simplify and clean up support 
for

serial devices.
If tty users cannot use the kernel support for automagic kill
switches/resets/whatever with kernel GPIO or whatever framework and must
continue supporting userspace GPIO and hacks for writing IO space from
userland for their devices there is just no point.

I mean it's fine to add support for your single pet device but if you 
are
to support non-trivial number of devices they don't get all perfect 
kernel
driver overnight. And if you need userspace GPIO for half of your 
devices
you can just continue using it for all to *simplify* your userspace 
code.


It has already happened for SPI devices and the implementation of the
userspace access to SPI is dragging for years.

Thanks

Michal

Re: [PATCH v2 0/9] Serial slave device bus

[msuchanek]

On 2017-01-16 23:54, Rob Herring wrote:

Here's a new version of the serdev bus support with all the review
feedback so far incorporated. I've left it named serdev for now pending
any further votes one way or the other, but I did rename the sysfs 
visible

portions to "serial".

There's still some discussion about what to do with devices that pass 
thru
data to userspace unmodified like GPS and could still use tty device 
for
the data path. IMO, we should treat this as a separate problem 
following

this series. Drivers we want to convert to serdev and already in the
kernel don't need this functionality.


The whole point of the serial bus is to simplify and clean up support 
for

serial devices.
If tty users cannot use the kernel support for automagic kill
switches/resets/whatever with kernel GPIO or whatever framework and must
continue supporting userspace GPIO and hacks for writing IO space from
userland for their devices there is just no point.

I mean it's fine to add support for your single pet device but if you 
are
to support non-trivial number of devices they don't get all perfect 
kernel
driver overnight. And if you need userspace GPIO for half of your 
devices
you can just continue using it for all to *simplify* your userspace 
code.


It has already happened for SPI devices and the implementation of the
userspace access to SPI is dragging for years.

Thanks

Michal

Re: [PATCH v2 0/9] Serial slave device bus

[Pavel Machek]

Hi!

> Here's a new version of the serdev bus support with all the review
> feedback so far incorporated. I've left it named serdev for now pending
> any further votes one way or the other, but I did rename the sysfs visible
> portions to "serial".
> 
> There's still some discussion about what to do with devices that pass thru
> data to userspace unmodified like GPS and could still use tty device for
> the data path. IMO, we should treat this as a separate problem following
> this series. Drivers we want to convert to serdev and already in the
> kernel don't need this functionality.
> 
> I need a SoB from Alan on his patch 2 and would like review from Alan and/or
> Peter on the locking in patch 5.
> 
> I have hacked up versions of the BT ldisc and TI ST drivers moved over to
> use the serdev bus. I have BT working on the HiKey board which has TI BT.
> With the serdev bus support, it eliminates the need for the TI userspace
> UIM daemon. I've made some progress cleaning up the TI-ST into proper
> patches and also got it working at 3Mbps.
> 
> Changelog is in individual patches. Previous version is here[1]. This
> series and the mentioned drivers can be found here[2].

Series looks good to me. Thanks for doing the work.

Best regards,
Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

Re: [PATCH v2 0/9] Serial slave device bus

[Pavel Machek]

Hi!

> Here's a new version of the serdev bus support with all the review
> feedback so far incorporated. I've left it named serdev for now pending
> any further votes one way or the other, but I did rename the sysfs visible
> portions to "serial".
> 
> There's still some discussion about what to do with devices that pass thru
> data to userspace unmodified like GPS and could still use tty device for
> the data path. IMO, we should treat this as a separate problem following
> this series. Drivers we want to convert to serdev and already in the
> kernel don't need this functionality.
> 
> I need a SoB from Alan on his patch 2 and would like review from Alan and/or
> Peter on the locking in patch 5.
> 
> I have hacked up versions of the BT ldisc and TI ST drivers moved over to
> use the serdev bus. I have BT working on the HiKey board which has TI BT.
> With the serdev bus support, it eliminates the need for the TI userspace
> UIM daemon. I've made some progress cleaning up the TI-ST into proper
> patches and also got it working at 3Mbps.
> 
> Changelog is in individual patches. Previous version is here[1]. This
> series and the mentioned drivers can be found here[2].

Series looks good to me. Thanks for doing the work.

Best regards,
Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) 
http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

[PATCH v2 0/9] Serial slave device bus

[Rob Herring]

Here's a new version of the serdev bus support with all the review
feedback so far incorporated. I've left it named serdev for now pending
any further votes one way or the other, but I did rename the sysfs visible
portions to "serial".

There's still some discussion about what to do with devices that pass thru
data to userspace unmodified like GPS and could still use tty device for
the data path. IMO, we should treat this as a separate problem following
this series. Drivers we want to convert to serdev and already in the
kernel don't need this functionality.

I need a SoB from Alan on his patch 2 and would like review from Alan and/or
Peter on the locking in patch 5.

I have hacked up versions of the BT ldisc and TI ST drivers moved over to
use the serdev bus. I have BT working on the HiKey board which has TI BT.
With the serdev bus support, it eliminates the need for the TI userspace
UIM daemon. I've made some progress cleaning up the TI-ST into proper
patches and also got it working at 3Mbps.

Changelog is in individual patches. Previous version is here[1]. This
series and the mentioned drivers can be found here[2].

Rob

[1] https://lkml.org/lkml/2017/1/6/411
[2] git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git serial-bus-v3


Alan Cox (1):
  tty_port: allow a port to be opened with a tty that has no file handle

Rob Herring (8):
  tty: move the non-file related parts of tty_release to new
tty_release_struct
  tty_port: make tty_port_register_device wrap
tty_port_register_device_attr
  tty: constify tty_ldisc_receive_buf buffer pointer
  tty_port: Add port client functions
  dt/bindings: Add a serial/UART attached device binding
  serdev: Introduce new bus for serial attached devices
  serdev: add a tty port controller driver
  tty_port: register tty ports with serdev bus

 .../devicetree/bindings/serial/slave-device.txt|  36 ++
 MAINTAINERS|   8 +
 drivers/char/Kconfig   |   1 +
 drivers/tty/Makefile   |   1 +
 drivers/tty/serdev/Kconfig |  16 +
 drivers/tty/serdev/Makefile|   5 +
 drivers/tty/serdev/core.c  | 421 +
 drivers/tty/serdev/serdev-ttyport.c| 240 
 drivers/tty/tty_buffer.c   |  19 +-
 drivers/tty/tty_io.c   |  52 ++-
 drivers/tty/tty_port.c |  58 ++-
 include/linux/serdev.h | 234 
 include/linux/tty.h|  12 +-
 13 files changed, 1062 insertions(+), 41 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/serial/slave-device.txt
 create mode 100644 drivers/tty/serdev/Kconfig
 create mode 100644 drivers/tty/serdev/Makefile
 create mode 100644 drivers/tty/serdev/core.c
 create mode 100644 drivers/tty/serdev/serdev-ttyport.c
 create mode 100644 include/linux/serdev.h

--
2.10.1

[PATCH v2 0/9] Serial slave device bus

[Rob Herring]

Here's a new version of the serdev bus support with all the review
feedback so far incorporated. I've left it named serdev for now pending
any further votes one way or the other, but I did rename the sysfs visible
portions to "serial".

There's still some discussion about what to do with devices that pass thru
data to userspace unmodified like GPS and could still use tty device for
the data path. IMO, we should treat this as a separate problem following
this series. Drivers we want to convert to serdev and already in the
kernel don't need this functionality.

I need a SoB from Alan on his patch 2 and would like review from Alan and/or
Peter on the locking in patch 5.

I have hacked up versions of the BT ldisc and TI ST drivers moved over to
use the serdev bus. I have BT working on the HiKey board which has TI BT.
With the serdev bus support, it eliminates the need for the TI userspace
UIM daemon. I've made some progress cleaning up the TI-ST into proper
patches and also got it working at 3Mbps.

Changelog is in individual patches. Previous version is here[1]. This
series and the mentioned drivers can be found here[2].

Rob

[1] https://lkml.org/lkml/2017/1/6/411
[2] git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git serial-bus-v3


Alan Cox (1):
  tty_port: allow a port to be opened with a tty that has no file handle

Rob Herring (8):
  tty: move the non-file related parts of tty_release to new
tty_release_struct
  tty_port: make tty_port_register_device wrap
tty_port_register_device_attr
  tty: constify tty_ldisc_receive_buf buffer pointer
  tty_port: Add port client functions
  dt/bindings: Add a serial/UART attached device binding
  serdev: Introduce new bus for serial attached devices
  serdev: add a tty port controller driver
  tty_port: register tty ports with serdev bus

 .../devicetree/bindings/serial/slave-device.txt|  36 ++
 MAINTAINERS|   8 +
 drivers/char/Kconfig   |   1 +
 drivers/tty/Makefile   |   1 +
 drivers/tty/serdev/Kconfig |  16 +
 drivers/tty/serdev/Makefile|   5 +
 drivers/tty/serdev/core.c  | 421 +
 drivers/tty/serdev/serdev-ttyport.c| 240 
 drivers/tty/tty_buffer.c   |  19 +-
 drivers/tty/tty_io.c   |  52 ++-
 drivers/tty/tty_port.c |  58 ++-
 include/linux/serdev.h | 234 
 include/linux/tty.h|  12 +-
 13 files changed, 1062 insertions(+), 41 deletions(-)
 create mode 100644 Documentation/devicetree/bindings/serial/slave-device.txt
 create mode 100644 drivers/tty/serdev/Kconfig
 create mode 100644 drivers/tty/serdev/Makefile
 create mode 100644 drivers/tty/serdev/core.c
 create mode 100644 drivers/tty/serdev/serdev-ttyport.c
 create mode 100644 include/linux/serdev.h

--
2.10.1