Hi Greg, On 06/08/2016 11:45 PM, Greg Kroah-Hartman wrote: > On Wed, Jun 08, 2016 at 03:56:04PM +0800, Lu Baolu wrote: >> Hi Greg, >> >> On 06/08/2016 12:45 PM, Greg Kroah-Hartman wrote: >>> On Thu, Jun 02, 2016 at 09:37:28AM +0800, Lu Baolu wrote: >>>> In some Intel platforms, a single usb port is shared between USB host >>>> and device controllers. The shared port is under control of a switch >>>> which is defined in the Intel vendor defined extended capability for >>>> xHCI. >>>> >>>> This patch adds the support to detect and create the platform device >>>> for the port mux switch. >>> Why do you need a platform device for this? You do nothing with this >>> device, why create it at all? >> In this patch series, I have a generic framework for port mux devices >> and two port mux drivers sitting on top the generic code. >> >> In this patch, I create a platform device for the real mux device in >> Intel Cherry Trail or Broxton SOCs. In it's driver, I registered a mux >> into the generic framework and handle the power management >> things in driver's pm entries (otherwise, the system can't be waken >> up from system suspend).:) >> >>> And why is it a platform device, isn't is really a PCI device? Why >>> would you ever find a "platform" device below a PCI device? Don't abuse >>> platform devices for things that aren't. It makes me want to delete >>> that whole interface more and more... >> Port mux devices are physical devices in Intel Cherry Trail and Broxton >> SOCs. It doesn't sit on any PCIe bus. But it maps its registers in xHCI >> space. OS kernel can enumerate it by looking up the xhci extended >> capability list with a vendor specific capability ID. > A physical device that maps registers into PCI space seems like a PCI > device of some type to me :) > > Again, I hate platform devices for obvious reasons like this... > It's not PCI configure space, but xhci's io memory. XHCI spec reserves a range in its extended capability list for vendor specific things. Intel's platform leverages this for the port mux device register mapping. It looks odd though. :) Best regards, Lu Baolu -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
