Re: /sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]
Michael Tokarev wrote: > Kay Sievers wrote: >> On Mon, 2007-12-17 at 08:29 +0300, Michael Tokarev wrote: > [] >>> How to distinguish char devices from block devices in sysfs? >>> Is the only way to read a symlink `subsystem' in the device >>> directory? >> By its subsystem value (block), from the symlink, from the environment, >> or from $1. > > Environment and $1 comes as arguments for hotplug helper, not > when scanning /sys/. By the way, that's one of reasons I asked about useful content in uevent files (but failed to provide a patch so far ;). In 2.6.23, those files ARE readable finally, but doesn't contain much info yet. /mjt -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: /sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]
Kay Sievers wrote:
> On Mon, 2007-12-17 at 08:29 +0300, Michael Tokarev wrote:
[]
>> How to distinguish char devices from block devices in sysfs?
>> Is the only way to read a symlink `subsystem' in the device
>> directory?
>
> By its subsystem value (block), from the symlink, from the environment,
> or from $1.
Environment and $1 comes as arguments for hotplug helper, not
when scanning /sys/.
>> For now, I've a shell code (used heavily in numerous places),
>> which looks like this:
>>
>> function makedev() {
>> ...
>> case $DEVPATH in
>> /block/*) TYPE=b ;;
>> *) TYPE=c ;;
>> esac
>> ...
>> mknod /dev/$DEV $TYPE $MAJOR $MINOR
>> }
>>
>> The only external process invocation in there is mknod, all
>> the rest is done using pure shell constructs. Is it really
>> necessary to spawn another process just to read a symlink
>> now? It will be almost 2 times slower
>
> No need.
It seems there IS a need now ;)
Thanks for the clarification.
/mjt
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Re: /sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]
On Mon, 2007-12-17 at 08:29 +0300, Michael Tokarev wrote:
> Kay Sievers wrote:
> > On Mon, 2007-12-17 at 09:43 +1100, Neil Brown wrote:
> >> On Saturday December 15, [EMAIL PROTECTED] wrote:
> >>> On Dec 14, 2007 7:26 AM, NeilBrown <[EMAIL PROTECTED]> wrote:
> Given an fd on a block device, returns a string like
>
> /block/sda/sda1
>
> which can be used to find related information in /sys.
> >>
> >>> As pointed out to when you came up with the idea, we can't do this. A
> >>> devpath
> >>> is a path to the device and will not necessarily start with "/block" for
> >>> block
> >>> devices. It may start with "/devices" and can be much longer than
> >>> BDEVNAME_SIZE*2 + 10.
> >> When you say "will not necessarily" can I take that to mean that it
> >> currently does, but it might (will) change??
> >
> > It's in -mm. The devpath for all block devices, like for all other
> > devices, will start with /devices/* if !SYSFS_DEPRECATED.
>
> This is the second time I come across this (planned?) change, and for
> the second time I can't understand it.
>
> How to distinguish char devices from block devices in sysfs?
> Is the only way to read a symlink `subsystem' in the device
> directory?
By its subsystem value (block), from the symlink, from the environment,
or from $1.
> For now, I've a shell code (used heavily in numerous places),
> which looks like this:
>
> function makedev() {
> ...
> case $DEVPATH in
> /block/*) TYPE=b ;;
> *) TYPE=c ;;
> esac
> ...
> mknod /dev/$DEV $TYPE $MAJOR $MINOR
> }
>
> The only external process invocation in there is mknod, all
> the rest is done using pure shell constructs. Is it really
> necessary to spawn another process just to read a symlink
> now? It will be almost 2 times slower
No need.
> (Sure thing this may be rewritten in C, but using shell it's
> MUCH easier to customize if necessary.)
$SUBSYSTEM == "block"
> Also, /sys/block/ directory is very easy to use currently, --
> unlike other /sys/ stuff which is way too deep and often
> placed in unknown/unexpected places (and /sys/class/ and
> /sys/bus/ directories are changing all the time).
/sys/block is still there and contains symlinks. And all this happens
only for !SYSFS_DEPRECATED.
> What's the benefit of moving things from /sys/block/ to
> /sys/devices/ ?
Unification. Block devices are "struct devices", use a class, use the
common driver core code instead of their own, show up in the tree, and
can be parents for other devices.
Kay
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Re: /sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]
On Mon, 2007-12-17 at 08:29 +0300, Michael Tokarev wrote:
Kay Sievers wrote:
On Mon, 2007-12-17 at 09:43 +1100, Neil Brown wrote:
On Saturday December 15, [EMAIL PROTECTED] wrote:
On Dec 14, 2007 7:26 AM, NeilBrown [EMAIL PROTECTED] wrote:
Given an fd on a block device, returns a string like
/block/sda/sda1
which can be used to find related information in /sys.
As pointed out to when you came up with the idea, we can't do this. A
devpath
is a path to the device and will not necessarily start with /block for
block
devices. It may start with /devices and can be much longer than
BDEVNAME_SIZE*2 + 10.
When you say will not necessarily can I take that to mean that it
currently does, but it might (will) change??
It's in -mm. The devpath for all block devices, like for all other
devices, will start with /devices/* if !SYSFS_DEPRECATED.
This is the second time I come across this (planned?) change, and for
the second time I can't understand it.
How to distinguish char devices from block devices in sysfs?
Is the only way to read a symlink `subsystem' in the device
directory?
By its subsystem value (block), from the symlink, from the environment,
or from $1.
For now, I've a shell code (used heavily in numerous places),
which looks like this:
function makedev() {
...
case $DEVPATH in
/block/*) TYPE=b ;;
*) TYPE=c ;;
esac
...
mknod /dev/$DEV $TYPE $MAJOR $MINOR
}
The only external process invocation in there is mknod, all
the rest is done using pure shell constructs. Is it really
necessary to spawn another process just to read a symlink
now? It will be almost 2 times slower
No need.
(Sure thing this may be rewritten in C, but using shell it's
MUCH easier to customize if necessary.)
$SUBSYSTEM == block
Also, /sys/block/ directory is very easy to use currently, --
unlike other /sys/ stuff which is way too deep and often
placed in unknown/unexpected places (and /sys/class/ and
/sys/bus/ directories are changing all the time).
/sys/block is still there and contains symlinks. And all this happens
only for !SYSFS_DEPRECATED.
What's the benefit of moving things from /sys/block/ to
/sys/devices/ ?
Unification. Block devices are struct devices, use a class, use the
common driver core code instead of their own, show up in the tree, and
can be parents for other devices.
Kay
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: /sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]
Kay Sievers wrote:
On Mon, 2007-12-17 at 08:29 +0300, Michael Tokarev wrote:
[]
How to distinguish char devices from block devices in sysfs?
Is the only way to read a symlink `subsystem' in the device
directory?
By its subsystem value (block), from the symlink, from the environment,
or from $1.
Environment and $1 comes as arguments for hotplug helper, not
when scanning /sys/.
For now, I've a shell code (used heavily in numerous places),
which looks like this:
function makedev() {
...
case $DEVPATH in
/block/*) TYPE=b ;;
*) TYPE=c ;;
esac
...
mknod /dev/$DEV $TYPE $MAJOR $MINOR
}
The only external process invocation in there is mknod, all
the rest is done using pure shell constructs. Is it really
necessary to spawn another process just to read a symlink
now? It will be almost 2 times slower
No need.
It seems there IS a need now ;)
Thanks for the clarification.
/mjt
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: /sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]
Michael Tokarev wrote: Kay Sievers wrote: On Mon, 2007-12-17 at 08:29 +0300, Michael Tokarev wrote: [] How to distinguish char devices from block devices in sysfs? Is the only way to read a symlink `subsystem' in the device directory? By its subsystem value (block), from the symlink, from the environment, or from $1. Environment and $1 comes as arguments for hotplug helper, not when scanning /sys/. By the way, that's one of reasons I asked about useful content in uevent files (but failed to provide a patch so far ;). In 2.6.23, those files ARE readable finally, but doesn't contain much info yet. /mjt -- To unsubscribe from this list: send the line unsubscribe linux-kernel in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
/sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]
Kay Sievers wrote:
> On Mon, 2007-12-17 at 09:43 +1100, Neil Brown wrote:
>> On Saturday December 15, [EMAIL PROTECTED] wrote:
>>> On Dec 14, 2007 7:26 AM, NeilBrown <[EMAIL PROTECTED]> wrote:
Given an fd on a block device, returns a string like
/block/sda/sda1
which can be used to find related information in /sys.
>>
>>> As pointed out to when you came up with the idea, we can't do this. A
>>> devpath
>>> is a path to the device and will not necessarily start with "/block" for
>>> block
>>> devices. It may start with "/devices" and can be much longer than
>>> BDEVNAME_SIZE*2 + 10.
>> When you say "will not necessarily" can I take that to mean that it
>> currently does, but it might (will) change??
>
> It's in -mm. The devpath for all block devices, like for all other
> devices, will start with /devices/* if !SYSFS_DEPRECATED.
This is the second time I come across this (planned?) change, and for
the second time I can't understand it.
How to distinguish char devices from block devices in sysfs?
Is the only way to read a symlink `subsystem' in the device
directory?
For now, I've a shell code (used heavily in numerous places),
which looks like this:
function makedev() {
...
case $DEVPATH in
/block/*) TYPE=b ;;
*) TYPE=c ;;
esac
...
mknod /dev/$DEV $TYPE $MAJOR $MINOR
}
The only external process invocation in there is mknod, all
the rest is done using pure shell constructs. Is it really
necessary to spawn another process just to read a symlink
now? It will be almost 2 times slower
(Sure thing this may be rewritten in C, but using shell it's
MUCH easier to customize if necessary.)
Also, /sys/block/ directory is very easy to use currently, --
unlike other /sys/ stuff which is way too deep and often
placed in unknown/unexpected places (and /sys/class/ and
/sys/bus/ directories are changing all the time).
What's the benefit of moving things from /sys/block/ to
/sys/devices/ ?
Thanks.
/mjt
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
/sys/block [was: [PATCH 007 of 7] md: Get name for block device in sysfs]
Kay Sievers wrote:
On Mon, 2007-12-17 at 09:43 +1100, Neil Brown wrote:
On Saturday December 15, [EMAIL PROTECTED] wrote:
On Dec 14, 2007 7:26 AM, NeilBrown [EMAIL PROTECTED] wrote:
Given an fd on a block device, returns a string like
/block/sda/sda1
which can be used to find related information in /sys.
As pointed out to when you came up with the idea, we can't do this. A
devpath
is a path to the device and will not necessarily start with /block for
block
devices. It may start with /devices and can be much longer than
BDEVNAME_SIZE*2 + 10.
When you say will not necessarily can I take that to mean that it
currently does, but it might (will) change??
It's in -mm. The devpath for all block devices, like for all other
devices, will start with /devices/* if !SYSFS_DEPRECATED.
This is the second time I come across this (planned?) change, and for
the second time I can't understand it.
How to distinguish char devices from block devices in sysfs?
Is the only way to read a symlink `subsystem' in the device
directory?
For now, I've a shell code (used heavily in numerous places),
which looks like this:
function makedev() {
...
case $DEVPATH in
/block/*) TYPE=b ;;
*) TYPE=c ;;
esac
...
mknod /dev/$DEV $TYPE $MAJOR $MINOR
}
The only external process invocation in there is mknod, all
the rest is done using pure shell constructs. Is it really
necessary to spawn another process just to read a symlink
now? It will be almost 2 times slower
(Sure thing this may be rewritten in C, but using shell it's
MUCH easier to customize if necessary.)
Also, /sys/block/ directory is very easy to use currently, --
unlike other /sys/ stuff which is way too deep and often
placed in unknown/unexpected places (and /sys/class/ and
/sys/bus/ directories are changing all the time).
What's the benefit of moving things from /sys/block/ to
/sys/devices/ ?
Thanks.
/mjt
--
To unsubscribe from this list: send the line unsubscribe linux-kernel in
the body of a message to [EMAIL PROTECTED]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
