linux-kernel - Re: kernel panic with simple driver

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Message-ID: <CAME+iucHOG+cvB2y9uLxwtLtas+E0nEfekgmN7gfj7YsT3kj+g@mail.gmail.com>
Date:	Wed, 10 Aug 2011 11:29:09 +0900
From:	"Murali K. Vemuri" <vemuri.muralikrishna@...il.com>
To:	Greg KH <greg@...ah.com>
Cc:	Ryan Mallon <rmallon@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: kernel panic with simple driver

On Wed, Aug 10, 2011 at 11:16 AM, Greg KH <greg@...ah.com> wrote:
> On Wed, Aug 10, 2011 at 10:33:28AM +0900, Murali K. Vemuri wrote:
>> There is no concurrent access to the timer. The design is that:
>> 1.Driver provides an IOCTL for start / stop
>> 2. when the driver receives START IOCTL, it toggles some GPIOs to ON / OFF.
>> 3. the GPIOs will be ON for 500 MSec and OFF for 500 MSec.
>> 4. Two successive START IOCTLs will not be honored.
>> 5. There is only one application that uses these IOCTLs
>> 6. When I receive a STOP IOCTL, I am doing :
>> if (timer_pending (&my_timer))
>> del_timer(&my_timer);
>
> What kind of driver is this?  For what type of hardware?
>
> Can't you control the gpios from userspace with out any need to write a
> kernel driver?
>

This driver is meant for controlling some LEDs. The CPU is OMAP 3530
and the OS is Android.
>From the user space, I could not control the GPIOs directly, and thus
I ended up supporting in the form of a simple driver.
I agree that these are better done from the user space, but as much as
I google'd studied, I could not find any better way to implement this.

If anyone has more info, that is also highly appreciated.
Thanks
Murali

> thanks,
>
> greg k-h
>
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