Gpio interrupt shall pass the signal to application

Gpio interrupt shall pass the signal to application

[jeshwanth Kumar N K]

Hello All,

I am writing a kernel module that shall pass the signal to application running in user space. So which signal i should use? And how to achieve this? Thank you.

Sent from my HTC
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Gpio interrupt shall pass the signal to application

[Fabio Pozzi]

I think you could use sysfs_notify to send the notification and use
select() or poll() to wait for changes in the sysfs file in the interrupt
handler routine. You can find an example of this in the gpio-fan driver.
Hope it helps

-- 
Saluti,
Fabio Pozzi
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Gpio interrupt shall pass the signal to application

[devendra.aaru]

On Sat, Oct 6, 2012 at 4:20 AM, jeshwanth Kumar N K
<jeshkumar555@gmail.com> wrote:
> Hello All,
>
> I am writing a kernel module that shall pass the signal to application
> running in user space. So which signal i should use? And how to achieve
> this? Thank you.
>
if any interrupt comes wake up a workqueue or a wait queue and
interrupt the poll wait.

that makes your application wakeup from a select.
> Sent from my HTC
>
>
> _______________________________________________
> Kernelnewbies mailing list
> Kernelnewbies at kernelnewbies.org
> http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
>

Gpio interrupt shall pass the signal to application

[Jonathan Neuschäfer]

On Sat, Oct 06, 2012 at 01:50:55PM +0530, jeshwanth Kumar N K wrote:
> Hello All,
> 
> I am writing a kernel module that shall pass the signal to application running in user space. So which signal i should use? And how to achieve this? Thank you.

What kind of information need to be transmitted from your device to the
application?


Jonathan Neusch?fer

Re: Gpio interrupt shall pass the signal to application

[jeshwanth Kumar N K]

Actually what I am doing is, I have 3 inputs to beaglebone from  BLDC motor hall sensor. If there is any change in any of 3 inputs, the kernel module has to send signal to my beaglebone. From the interrupt my application reads the input from sysfs and pass the next sequence to pwm. PWM I am using userspace only. 
So is my design right for handling fast input change, I mean 50 micro seconds ? Any suggestion ? I am new to device driver concept, please suggest.
Thanks :)

Sent from my HTC

----- Reply message -----
From: "Jonathan Neusch?fer" <j.neuschaefer@gmx.net>
Date: Sat, Oct 6, 2012 10:29 pm
Subject: Gpio interrupt shall pass the signal to application
To: "jeshwanth Kumar N K" <jeshkumar555@gmail.com>
Cc: "kernelnewbies" <kernelnewbies@kernelnewbies.org>


On Sat, Oct 06, 2012 at 01:50:55PM +0530, jeshwanth Kumar N K wrote:
> Hello All,
> 
> I am writing a kernel module that shall pass the signal to application running in user space. So which signal i should use? And how to achieve this? Thank you.

What kind of information need to be transmitted from your device to the
application?


Jonathan Neusch?fer
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Gpio interrupt shall pass the signal to application

[Fabio Pozzi]

Hi Jeshwanth,
I'm not an expert in kernel development, but I think that if you receive an
interrupt every 50_micro_seconds IMHO you should definitely deal with it in
kernel mode and maybe also think about enabling Real Time to be more
certain about kernel latencies and scheduling.
The context switch time between kernel and user space I think it's too long
to delegate the elaboration to userspace.

-- 
Fabio Pozzi
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Re: Gpio interrupt shall pass the signal to application

[jeshwanth Kumar N K]

Hi Fabio,

Thanks for the reply. Ya I got your point, and I did the same thing by exporting the sysfs gpio and poll for value attribute It works fine but the thing is time. Actually my interrupts may be every 50 micro seconds. So I thought of dealing in kernel mode itself. What's your suggestion ?
Sent from my HTC

----- Reply message -----
From: "Fabio Pozzi" <pozzi.fabio@gmail.com>
Date: Sat, Oct 6, 2012 2:29 pm
Subject: Gpio interrupt shall pass the signal to application
To: "jeshwanth Kumar N K" <jeshkumar555@gmail.com>
Cc: "kernelnewbies" <kernelnewbies@kernelnewbies.org>


I think you could use sysfs_notify to send the notification and use
select() or poll() to wait for changes in the sysfs file in the interrupt
handler routine. You can find an example of this in the gpio-fan driver.
Hope it helps

-- 
Saluti,
Fabio Pozzi
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