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usb/uas: only bind if the hcd supports SG

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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>
This commit is contained in:
Sebastian Andrzej Siewior 2012-01-11 12:42:32 +01:00 committed by Sarah Sharp
parent b603669842
commit c898add51c
1 changed files with 19 additions and 6 deletions
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25
drivers/usb/storage/uas.c
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@ -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>
@ -621,22 +622,34 @@ 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;