On Fri, Jun 19, 2015 at 6:06 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: > [-cc Dexuan, Matthew (bounced)] > [+cc Mathias, since MAINTAINERS mentions USB, Intel, and you in one entry :)] > > On Fri, Jun 19, 2015 at 5:42 PM, Bjorn Helgaas <bhelgaas@xxxxxxxxxx> wrote: >> We checked for "dev->class == PCI_CLASS_SERIAL_USB", but dev->class >> contains the entire three-byte base class/sub-class/interface, while >> PCI_CLASS_SERIAL_USB is only the two-byte base class/sub-class. >> >> This error meant that we used the Intel device-specific reset on devices >> with class code 0x000c03 instead of those with class code 0x0c03xx. >> 0x000c03 is a reserved value in the 0x00 backwards compatibility base class >> and shouldn't match any devices, so I think reset_intel_generic_dev() >> always failed. >> >> Shift dev->class to discard the interface byte before comparing with >> PCI_CLASS_SERIAL_USB. >> >> Fixes: aeb30016fec3 ("PCI: add Intel USB specific reset method") >> Signed-off-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx> >> CC: Dexuan Cui <dexuan.cui@xxxxxxxxx> >> CC: Yu Zhao <yu.zhao@xxxxxxxxx> >> --- >> drivers/pci/quirks.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/drivers/pci/quirks.c b/drivers/pci/quirks.c >> index 8bc60c2..356a401 100644 >> --- a/drivers/pci/quirks.c >> +++ b/drivers/pci/quirks.c >> @@ -3358,7 +3358,7 @@ static int reset_intel_generic_dev(struct pci_dev *dev, int probe) >> int pos; >> >> /* only implement PCI_CLASS_SERIAL_USB at present */ >> - if (dev->class == PCI_CLASS_SERIAL_USB) { >> + if ((dev->class >> 8) == PCI_CLASS_SERIAL_USB) { > > I'm a little bit concerned about this change because it *looks* like > this has always been broken, but I assume it was tested and somebody > would have noticed. Unless we get confirmation that somebody cares about reset_intel_generic_dev() and it has been tested, I'm inclined to revert aeb30016fec3 ("PCI: add Intel USB specific reset method") instead of applying this fix. I think reset_intel_generic_dev() always returns -ENOTTY except for devices with "class == 0x000c03", which is an invalid class code. If I "fix" it by putting in the shift, it will start poking at config space on Intel USB devices. I have no way of testing that, and I haven't seen a problem report related to this, so a change is just as likely to break something as to fix something. So the safest thing looks like just dropping the quirk altogether, which shouldn't change behavior at all. >> pos = pci_find_capability(dev, PCI_CAP_ID_VNDR); >> if (!pos) >> return -ENOTTY; >> -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html