usb/uas: only bind if the hcd supports SG (c898add5) · Commits · 戴 / test

The UAS driver requires SG support by the HCD operating the device. This patch stops UAS from operating on a HCD without sg support and prints a message to let him know. The spec says: |For [USB2] backward compatibility, the device shall present [BOT] as |alternate interface zero (primary) and [UAS] as alternate interface one |(secondary). A device which does not need backward compatibility with |[BOT] shall present [UAS] as alternate interface zero. In [USB2] |systems, the [BOT] driver or an associated filter driver may need to |issue a SET INTERFACE request for alternate interface one and then allow |the [UAS] driver to load. If the user used usb_modeswitch to switch to UAS then he can go back to BOT or use a different HCD. In case UAS is the only interface then there is currently no way out. In future usb_sg_wait() should be extended to provide a non-blocking interface so it can work with the UAS driver. Signed-off-by:

Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by:

Sarah Sharp <sarah.a.sharp@linux.intel.com>

drivers/usb/storage/uas.c

+19 −6

Original line number	Diff line number	Diff line
		@@ -13,6 +13,7 @@
		#include <linux/types.h>
		#include <linux/module.h>
		#include <linux/usb.h>
		#include <linux/usb/hcd.h>
		#include <linux/usb/storage.h>

		#include <scsi/scsi.h>
		@@ -621,23 +622,35 @@ static int uas_is_interface(struct usb_host_interface *intf)
		intf->desc.bInterfaceProtocol == USB_PR_UAS);
		}

		static int uas_isnt_supported(struct usb_device *udev)
		{
		struct usb_hcd *hcd = bus_to_hcd(udev->bus);

		dev_warn(&udev->dev, "The driver for the USB controller %s does not "
		"support scatter-gather which is\n",
		hcd->driver->description);
		dev_warn(&udev->dev, "required by the UAS driver. Please try an"
		"alternative USB controller if you wish to use UAS.\n");
		return -ENODEV;
		}

		static int uas_switch_interface(struct usb_device *udev,
		struct usb_interface *intf)
		{
		int i;

		if (uas_is_interface(intf->cur_altsetting))
		return 0;
		int sg_supported = udev->bus->sg_tablesize != 0;

		for (i = 0; i < intf->num_altsetting; i++) {
		struct usb_host_interface *alt = &intf->altsetting[i];
		if (alt == intf->cur_altsetting)
		continue;
		if (uas_is_interface(alt))

		if (uas_is_interface(alt)) {
		if (!sg_supported)
		return uas_isnt_supported(udev);
		return usb_set_interface(udev,
		alt->desc.bInterfaceNumber,
		alt->desc.bAlternateSetting);
		}
		}

		return -ENODEV;
		}

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