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

Thomas Gleixner
2008-05-24T22:22:36Z

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.

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:

while (!stop) {

/* wait for interrupt */
read(fd);

do_stuff();

/*reenable interrupt */
write(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.

Thanks,

tglx