On Tue, Nov 24, 2009 at 10:19:41AM -0500, Alan Stern wrote:
> There appears to be a problem in usb_reset_and_verify_device(), where
> the old altsettings are restored. Initially you restore the old
> config, which allocates bandwidth for altsetting 0. Then the routine
> calls usb_set_interface() to restore the old altsetting. But the
> cur_alt argument passed to usb_hcd_alloc_bandwidth() will be the old
> altsetting, not altsetting 0. To fix this, you'll have to set
> intf->cur_altsetting to point to altsetting 0 before
> usb_reset_and_verify_device() calls usb_set_interface().
Ok, I'll fix that.
> There are several places where usbcore searches for altsetting 0. Can
> they all use a single subroutine?
Are you talking about lines like this?
/* Dig the endpoints for alt setting 0 out of the
* interface cache for this interface
*/
intf_cache = new_config->intf_cache[i];
for (j = 0; j < intf_cache->num_altsetting; j++) {
if (intf_cache->altsetting[j].desc.bAlternateSetting == 0)
alt = &intf_cache->altsetting[j];
}
if (!alt) {
printk(KERN_DEBUG "Did not find alt setting 0 for intf %d\n", i);
continue;
}
Sure, I can put that into a subroutine.
On a similar note, what if the device doesn't have an alternate interface
setting 0? What should usb_hcd_alloc_bandwidth() do when installing a new
configuration with an interface that doesn't have an alt setting 0? What
alternate interface setting will the device think it's at after it receives the
set configuration command?
I see that usb_reset_configuration() has this note:
/* No altsetting 0? We'll assume the first altsetting.
* We could use a GetInterface call, but if a device is
* so non-compliant that it doesn't have altsetting 0
* then I wouldn't trust its reply anyway.
*/
if (!alt)
alt = &intf->altsetting[0];
If I follow that example, usb_hcd_alloc_bandwidth() should pick the first alt
setting if there is no alt setting 0 for a new configuration. That means I
need to set intf->cur_altsetting to that alt setting before
usb_reset_and_verify_device() calls usb_set_interface().
Sarah Sharp
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