Re: kernel panic with simple driver

[Ryan Mallon]

On 10/08/11 12:29, Murali K. Vemuri wrote:
> 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.

If you have CONFIG_GPIO_SYSFS enabled then you can access the gpios 
directly via sysfs. See Documentation/gpio.txt for details.

~Ryan

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/