Re: [PATCH 1/1] UIO: Add a write() function to enable/disable interrupts

Tom Spink
2008-05-24T22:34:42Z

2008/5/24 Thomas Gleixner <tglx@linutronix.de>:
> On Fri, 23 May 2008, Greg KH wrote:
>
>> On Fri, May 23, 2008 at 01:55:57PM +0200, Hans J. Koch wrote:
>> > Sometimes it is necessary to enable/disable the interrupt of a UIO device
>> > from the userspace part of the driver. With this patch, the UIO kernel driver
>> > can implement an "irqcontrol()" function that does this. Userspace can write
>> > an s32 value to /dev/uioX (usually 0 or 1 to turn the irq off or on). The
>> > UIO core will then call the driver's irqcontrol function.
>>
>> Why not just a new sysfs file for the uio device, irq_enabled, or
>> something like that? That way our main read/write path is left alone.

Hi,

> It makes a certain amount of sense to use write. You hold the device
> file descriptor anyway for the read (wait for interrupt) operation,
> so using the same file descriptor is not a too bad idea:

What do you think about my ioctl idea, earlier in the thread?

> while (!stop) {
>
> /* wait for interrupt */
> read(fd);
>
> do_stuff();
>
> /*reenable interrupt */
> write(fd);
> }

So, instead of write, you'd use ioctl(fd, ...).

> I thought about using a sysfs entry for a while, but looking at the
> actual use case made the write() solution a more natural choice.

I thought ioctl would be more natural, as [en,dis]abling interrupts is
a "controlling" operation :-)

> Thanks,
>
> tglx

--
Tom Spink