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... greg k-h -- 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
