Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit c898add5 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Sarah Sharp
Browse files

usb/uas: only bind if the hcd supports SG 



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: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@linux.intel.com>
parent b6036698

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;

}