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Commit3fce396

Browse files
m-v-bgregkh
authored andcommitted
usbcore/driver: Accommodate usbip
Commit88b7381 ("USB: Select better matching USB drivers whenavailable") inadvertently broke usbip functionality. The commit inquestion allows USB device drivers to be explicitly matched withUSB devices via the use of driver-provided identifier tables andmatch functions, which is useful for a specialised device driverto 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 anunconditional "return 1" statement, which allowed user-space to bindUSB devices to the usbip_host device driver, if desired. However,the aforementioned commit changed the default/fallback returnvalue to zero. This breaks device drivers such as usbip_host, sothis commit restores the legacy behaviour, but only if a devicedriver does not have an id_table and a match() function.In addition, if usb_device_match is called for a device driverand device pair where the device does not match the id_table of thedevice driver in question, then the device driver will be disqualifiedfor the device. This allows avoiding the default case of "return 1",which prevents undesirable probe() calls to a driver even thoughits id_table did not match the device.Finally, this commit changes the specialised-driver-to-generic-drivertransition code so that when a device driver returns -ENODEV, a moregeneric device driver is only considered if the current device driverdoes not have an id_table and a match() function. This ensures that"generic" drivers such as usbip_host will not be considered specialiseddevice drivers and will not cause the device to be locked in to thegeneric device driver, when a more specialised device driver could betried.All of these changes restore usbip functionality without regressions,ensure that the specialised/generic device driver selection logic worksas expected with the usb and apple-mfi-fastcharge drivers, and do notnegatively affect the use of devices provided by dummy_hcd.Fixes:88b7381 ("USB: Select better matching USB drivers when available")Cc: <stable@vger.kernel.org> # 5.8Cc: 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.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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‎drivers/usb/core/driver.c‎

Lines changed: 31 additions & 6 deletions
Original file line numberDiff line numberDiff line change
@@ -269,8 +269,30 @@ static int usb_probe_device(struct device *dev)
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if (error)
270270
returnerror;
271271

272+
/* Probe the USB device with the driver in hand, but only
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* defer to a generic driver in case the current USB
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* device driver has an id_table or a match function; i.e.,
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* when the device driver was explicitly matched against
276+
* a device.
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*
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* If the device driver does not have either of these,
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* then we assume that it can bind to any device and is
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* not truly a more specialized/non-generic driver, so a
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* return value of -ENODEV should not force the device
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* to be handled by the generic USB driver, as there
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* can still be another, more specialized, device driver.
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*
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* This accommodates the usbip driver.
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*
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* TODO: What if, in the future, there are multiple
288+
* specialized USB device drivers for a particular device?
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* In such cases, there is a need to try all matching
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* specialised device drivers prior to setting the
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* use_generic_driver bit.
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*/
272293
error=udriver->probe(udev);
273-
if (error==-ENODEV&&udriver!=&usb_generic_driver) {
294+
if (error==-ENODEV&&udriver!=&usb_generic_driver&&
295+
(udriver->id_table||udriver->match)) {
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udev->use_generic_driver=1;
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return-EPROBE_DEFER;
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}
@@ -831,14 +853,17 @@ static int usb_device_match(struct device *dev, struct device_driver *drv)
831853
udev=to_usb_device(dev);
832854
udrv=to_usb_device_driver(drv);
833855

834-
if (udrv->id_table&&
835-
usb_device_match_id(udev,udrv->id_table)!=NULL) {
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return1;
837-
}
856+
if (udrv->id_table)
857+
returnusb_device_match_id(udev,udrv->id_table)!=NULL;
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if (udrv->match)
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returnudrv->match(udev);
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return0;
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/* If the device driver under consideration does not have a
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* id_table or a match function, then let the driver's probe
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* function decide.
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*/
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return1;
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}elseif (is_usb_interface(dev)) {
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structusb_interface*intf;

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