[rt2x00-users] [RFC] rt2x00: Use tasklets for rt2x00usb

Helmut Schaa helmut.schaa at googlemail.com
Thu Jul 22 16:53:17 AEST 2010


Am Donnerstag 22 Juli 2010 schrieb Mark Asselstine:
> On Wed, Jul 21, 2010 at 6:32 PM, Ivo van Doorn <ivdoorn at gmail.com> wrote:
> > This updates the rt2x00usb driver to use tasklets for handling interrupts.
> > This simplifies the code in rt2x00lib since it no longer needs to check if the
> > device is USB or PCI to decide which mac80211 function should be used.
> >
> > This patch is work in progress, but I would to hear if there are any comments
> > on the approach taken.
> >
> > Signed-off-by: Ivo van Doorn <IvDoorn at gmail.com>
> > ---
> 
> Ivo,  I know it has been far too long since I have done any work on
> this project and I am far from an expert so feel free hit the delete
> key... that being said. Tasklets are used less and less in the kernel
> as there are now other mechanisms which offer the same flexibility.
> Seeing this trend makes me feel rt2x00 is moving in the opposite
> direction. Have you looked at threaded interrupts (which are now in
> mainline) as an alternative? If I can get my development environment
> setup quickly I will try to do better then these few words and
> actually attempt an implementation if you think it is worth it.

I agree. We switched all rt2x00 PCI drivers to use threaded interrupts
already. However, since the USB versions don't have something like an
interrupt handler I don't know how we could move the rx/tx handling
into process context without introducing delays (for example when using a
workqueue) and concurrency.

b43 for example also uses threaded interrupts for PCI devices and implemented
a similar technique for SDIO. It takes care of scheduling the interrupt thread
on its own. Not sure if that would be useful for rt2x00 USB devices.

Helmut




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