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

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Message-ID: <20080527175552.GB11645@suse.de>
Date:	Tue, 27 May 2008 10:55:52 -0700
From:	Greg KH <gregkh@...e.de>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	"Hans J. Koch" <hjk@...utronix.de>,
	Uwe Kleine-K??nig <Uwe.Kleine-Koenig@...i.com>,
	linux-kernel@...r.kernel.org,
	Jan Altenberg <jan.altenberg@...utronix.de>,
	Magnus Damm <magnus.damm@...il.com>
Subject: Re: [PATCH 1/1] UIO: Add a write() function to enable/disable
	interrupts

On Sun, May 25, 2008 at 12:22:20AM +0200, Thomas Gleixner wrote:
> 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.

Ok, that makes sense, I can accept this.

Anyone care to respin the patches with the latest updates and send them
to me?

thanks,

greg k-h
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