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authorAlan Stern <stern@rowland.harvard.edu>2009-02-26 10:21:02 -0500
committerGreg Kroah-Hartman <gregkh@suse.de>2009-03-24 16:20:38 -0700
commit4fe0387afa893b44c5a21b9bfbb0888354ef4656 (patch)
treeb86045c34fab6ff5146dd3ca6be70d54514a1359 /samples
parent77aa2b5878f48d6ab6e0c412cc9214c845483475 (diff)
USB: don't send Set-Interface after reset
This patch (as1221) changes the way usbcore reinitializes a device following a reset or a reset-resume. Currently we call usb_set_interface() for every interface in the active configuration; this is to put the interface into the same altsetting as before the reset and to make sure that the host's endpoint state matches the device's endpoint state. However, sending a Set-Interface request is a waste of time if an interface was already in altsetting 0 before the reset, since it is certainly in altsetting 0 afterward. In addition, many devices can't handle Set-Interface requests -- they crash when they receive them. So instead, the patch adds code to check each interface. If the interface wasn't in altsetting 0 before the reset, we go head with the Set-Interface request as before. But if it was then we skip sending the Set-Interface request, and we clear out the host-side endpoint state by calling usb_disable_interface() followed by usb_enable_interface(). The patch also adds a couple of new comments to explain what's going on. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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