usbcore/driver: Accommodate usbip

Commit 88b7381a939d ("USB: Select better matching USB drivers when
available") inadvertently broke usbip functionality. The commit in
question allows USB device drivers to be explicitly matched with
USB devices via the use of driver-provided identifier tables and
match functions, which is useful for a specialised device driver
to be chosen for a device that can also be handled by another,
more generic, device driver.

Prior, the USB device section of usb_device_match() had an
unconditional "return 1" statement, which allowed user-space to bind
USB devices to the usbip_host device driver, if desired. However,
the aforementioned commit changed the default/fallback return
value to zero. This breaks device drivers such as usbip_host, so
this commit restores the legacy behaviour, but only if a device
driver does not have an id_table and a match() function.

In addition, if usb_device_match is called for a device driver
and device pair where the device does not match the id_table of the
device driver in question, then the device driver will be disqualified
for the device. This allows avoiding the default case of "return 1",
which prevents undesirable probe() calls to a driver even though
its id_table did not match the device.

Finally, this commit changes the specialised-driver-to-generic-driver
transition code so that when a device driver returns -ENODEV, a more
generic device driver is only considered if the current device driver
does not have an id_table and a match() function. This ensures that
"generic" drivers such as usbip_host will not be considered specialised
device drivers and will not cause the device to be locked in to the
generic device driver, when a more specialised device driver could be
tried.

All of these changes restore usbip functionality without regressions,
ensure that the specialised/generic device driver selection logic works
as expected with the usb and apple-mfi-fastcharge drivers, and do not
negatively affect the use of devices provided by dummy_hcd.

Fixes: 88b7381a939d ("USB: Select better matching USB drivers when available")
Cc: <stable@vger.kernel.org> # 5.8
Cc: Bastien Nocera <hadess@hadess.net>
Cc: Valentina Manea <valentina.manea.m@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: <syzkaller@googlegroups.com>
Tested-by: Andrey Konovalov <andreyknvl@google.com>
Acked-by: Shuah Khan <skhan@linuxfoundation.org>
Signed-off-by: M. Vefa Bicakci <m.v.b@runbox.com>
Link: https://lore.kernel.org/r/20200922110703.720960-5-m.v.b@runbox.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

0 files changed, 0 insertions, 0 deletions