Re: Request for guidance

2016-05-23 Thread sanjeev sharma 
Hi Abhishek,

There are some open source project where you can contribute too but I would
suggest first you to work on Kernel Bugs available at
https://bugzilla.kernel.org. This would boost your confidence.

Regards
Sanjeev Sharma



On Tue, May 24, 2016 at 7:06 AM, Abhishek  wrote:

> Hi All,
>
> I am an Embedded Software Engineer with 3+ years of experience. I am
> fascinated by kernel development and want to be a device driver developer.
>
> I have done following so far.
> #Studied LDD3.
> #Subscribed to eudyptula challenge and submitted solution
> for 4th task(waiting for next task).
> #Have compiled and installed kernel successfully on multiple boards.
>
> I want to start contributing to kernel so I looked into staging and
> found that I can not work on TODO unless I have required hardware to
> test patch (which unfortunately I don't have).
>
> Requesting you to guide me about how to start working on kernel/device
> drivers development.
>
> Thanks,
> Abhishek
>
>
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Request for guidance

2016-05-23 Thread Abhishek 
Hi All,

I am an Embedded Software Engineer with 3+ years of experience. I am
fascinated by kernel development and want to be a device driver developer.

I have done following so far.
#Studied LDD3.
#Subscribed to eudyptula challenge and submitted solution
for 4th task(waiting for next task).
#Have compiled and installed kernel successfully on multiple boards.

I want to start contributing to kernel so I looked into staging and
found that I can not work on TODO unless I have required hardware to
test patch (which unfortunately I don't have).

Requesting you to guide me about how to start working on kernel/device drivers 
development.

Thanks,
Abhishek


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Re: Changing the default scheduler

2016-05-23 Thread Renato Utsch 
The idea is to patch the kernel. I am trying to discover how I can set the
default scheduler for new processes, so that I can test the behavior of any
schedulers that I may write. Do you have any ideas?

Em Seg, 23 de mai de 2016 10:05 AM, Mulyadi Santosa <
mulyadi.sant...@gmail.com> escreveu:

> On Fri, May 20, 2016 at 6:51 AM, Renato Utsch 
> wrote:
>
>> Hello,
>>
>> I am a new developer trying to learn how to tinker with the kernel. I
>> searched on the internet but couldn't find much info about this (and
>> couldn't find any info up to date).
>>
>> My question is, how does the kernel decide which is the default scheduler
>> that all processes start with? I can change the scheduler of a process by
>> sched_setscheduler(), but how do I change *all* processes from using the
>> CFS scheduler to, for example, the RR scheduler?
>>
>> Sorry if this is too basic, but I don't know where to search for this. If
>> you guys could point me places where I can learn more about this, I would
>> be grateful.
>>
>> ___
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>>
>>
> Hi..
>
> putting aside scheduler plugins module that once exist and maintained (not
> sure now), I guess the only way to switch to new scheduler is to patch your
> kernel first (if you haven't do that) with scheduler patch such as Con
> Kolivas BFS and reboot to that new kernel.
>
>
> --
> regards,
>
> Mulyadi Santosa
> Freelance Linux trainer and consultant
>
> blog: the-hydra.blogspot.com
> training: mulyaditraining.blogspot.com
>
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Re: is there any actual usage of the device tree node "/chosen@0"?

2016-05-23 Thread Greg KH 
On Mon, May 23, 2016 at 01:51:36PM -0400, Robert P. J. Day wrote:
> so there are apparently three files that *check* for that alternate
> name, but not a single .dts or .dtsi that actually uses it. is there
> any value to that alternate name?

Why are you asking that here and not on the device tree mailing list?

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is there any actual usage of the device tree node "/chosen@0"?

2016-05-23 Thread Robert P. J. Day 

  currently perusing the kernel code for device tree processing and
stumbled across this in drivers/of/base.c:

  void of_alias_scan(void * (*dt_alloc)(u64 size, u64 align))
  {
struct property *pp;

of_aliases = of_find_node_by_path("/aliases");
of_chosen = of_find_node_by_path("/chosen");
if (of_chosen == NULL)
of_chosen = of_find_node_by_path("/chosen@0");  ?

if (of_chosen) {
... snip ...

that pretty clearly says that "/chosen@0" is an equivalent node name
for "/chosen", correct? but why was that equivalence first defined?

  if i scan the entire kernel source tree, this is all i get:

$ grep -r "/chosen@0" *
arch/powerpc/boot/oflib.c:  chosen = of_finddevice("/chosen@0");
drivers/of/base.c:  of_chosen = of_find_node_by_path("/chosen@0");
drivers/of/fdt.c:   offset = fdt_path_offset(fdt, "/chosen@0");
$

so there are apparently three files that *check* for that alternate
name, but not a single .dts or .dtsi that actually uses it. is there
any value to that alternate name?

rday

-- 


Robert P. J. Day Ottawa, Ontario, CANADA
http://crashcourse.ca

Twitter:   http://twitter.com/rpjday
LinkedIn:   http://ca.linkedin.com/in/rpjday



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Re: Finding GPIO names under Linux

2016-05-23 Thread Mike Krinkin 
On Mon, May 23, 2016 at 04:05:23PM +0200, Johannes Thoma wrote:
> Dear list,
> 
> I am writing a driver which uses the "new" descriptor interface of the 
> GPIO library. As far as I have understood it, gpiod_get(8) is the way to 
> allocate (and also lock?) GPIOs pins for use. My question is how do I 
> find what to pass as the con_id parameter (this should identify the pin 
> but please correct me if I am wrong, in that case how to I tell 
> gpiod_get which pin I want?). Is there a file somewhere where I can find 
> the pin names of my hardware (which is a raspberry 1 for now), something 
> like /sys/class/gpio/xxx/gpio_pin_names or so, or do I have to look them 
> up in the device tree or somewhere else? Or do I have to
> configure the pin somewhere in the device tree? What I would like to
> do is offer an interface (via configfs) where the pins the sensor is
> attached can be configured dynamically at run-time.
> 
> The driver itself is OpenSource (GPL) and can be obtained at
> 
> http://github.com/johannesthoma/linux-hc-sro4
> 
> (iio branch is currently the dev branch where this problem occurs).
> 
> Thanks a lot,

A while ago i was trying to understand how to use descriptor based interface
playing with my RPi, you can find ressults here:

https://github.com/krinkinmu/rpi-gpio-example

(*.tex files are in russian, sorry), IFAIU, you have to specify name in
device tree before you can use it.

> 
> - Johannes
> 
> 
> 
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Finding GPIO names under Linux

2016-05-23 Thread Johannes Thoma 
Dear list,

I am writing a driver which uses the "new" descriptor interface of the 
GPIO library. As far as I have understood it, gpiod_get(8) is the way to 
allocate (and also lock?) GPIOs pins for use. My question is how do I 
find what to pass as the con_id parameter (this should identify the pin 
but please correct me if I am wrong, in that case how to I tell 
gpiod_get which pin I want?). Is there a file somewhere where I can find 
the pin names of my hardware (which is a raspberry 1 for now), something 
like /sys/class/gpio/xxx/gpio_pin_names or so, or do I have to look them 
up in the device tree or somewhere else? Or do I have to
configure the pin somewhere in the device tree? What I would like to
do is offer an interface (via configfs) where the pins the sensor is
attached can be configured dynamically at run-time.

The driver itself is OpenSource (GPL) and can be obtained at

http://github.com/johannesthoma/linux-hc-sro4

(iio branch is currently the dev branch where this problem occurs).

Thanks a lot,

- Johannes



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Re: Changing the default scheduler

2016-05-23 Thread Mulyadi Santosa 
On Fri, May 20, 2016 at 6:51 AM, Renato Utsch  wrote:

> Hello,
>
> I am a new developer trying to learn how to tinker with the kernel. I
> searched on the internet but couldn't find much info about this (and
> couldn't find any info up to date).
>
> My question is, how does the kernel decide which is the default scheduler
> that all processes start with? I can change the scheduler of a process by
> sched_setscheduler(), but how do I change *all* processes from using the
> CFS scheduler to, for example, the RR scheduler?
>
> Sorry if this is too basic, but I don't know where to search for this. If
> you guys could point me places where I can learn more about this, I would
> be grateful.
>
> ___
> Kernelnewbies mailing list
> Kernelnewbies@kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>
>
Hi..

putting aside scheduler plugins module that once exist and maintained (not
sure now), I guess the only way to switch to new scheduler is to patch your
kernel first (if you haven't do that) with scheduler patch such as Con
Kolivas BFS and reboot to that new kernel.


-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com
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