Re: kernel panic with simple driver

From: Murali K. Vemuri
Date: Tue Aug 09 2011 - 22:29:16 EST

On Wed, Aug 10, 2011 at 11:16 AM, Greg KH <greg@xxxxxxxxx> 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,
> greg k-h
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