Re: What to do with all of the USB UHCI drivers in the kernel ?

[Greg KH <greg@kroah.com>]

On Tue, May 21, 2002 at 06:04:21PM -0700, Maksim (Max) Krasnyanskiy wrote:
> 
> >IMO, I think testing with usb-uhci.c and uhci.c is still useful, but
> >testing with the -hcd variants is the most ideal since that will be the
> >final code base.
> 
> Ok. Here is feedback on 2.5.17 uhci-hcd and usb-uhci-hcd.
> I did not notice any difference in behavior. Both have the same 
> performance, just like 2.4.19-pre8.
> 
> One-shot interrupt transfers are broken in *-hcd drivers. core/hcd.c 
> returns EINVAL if urb->interval==0.
> My Broadcom FW loader (uses usbdevfs) needs one-shot interrupts. So in 
> order to test Broadcom devices
> I changed to hcd.c to allow urb->interval==0. With that change uhci-hcd 
> works just fine, I can load fw and
> use the device. But usb-uhci-hcd kills the machine pretty hard (hw reset 
> needed).
> 
> Here is a patch for hcd.c.

Thanks for the patch.

> On a side note. Why are URBs still not SLABified ?
> Drivers still have those silly urb pools and stuff. I thought you guys were 
> gonna fix that.

It hasn't been proven that it's really needed.  95% of the current
drivers create their urbs when the device is plugged in, and then free
them when they are removed.  Making that kind of allocation into a slab
is a bit silly :)

Now if more drivers start doing fun stuff like the visor.c driver does
in the 2.5 tree, then it might make more sense to create a URB specific
slab.

thanks,

greg k-h