Commit 5dc50c35 authored Jul 12, 2013 by Hans de Goede Committed by Greg Kroah-Hartman Jul 25, 2013

usbfs: Allow printer class 'get_device_id' without needing to claim the intf



For certain (HP) printers the printer device_id does not only contain a
static part identifying the printer, but it also contains a dynamic part
giving printer status, ink level, etc.

To get to this info various userspace utilities need to be able to make a
printer class 'get_device_id' request without first claiming the interface
(as that is in use for the actual printer driver).

Since the printer class 'get_device_id' request does not change interface
settings in anyway, allowing this without claiming the interface should not
cause any issues.

CC: Sanjay Kumar <sanjay.kumar14@hp.com>
CC: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent aaf6b52d

drivers/usb/core/devio.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -725,15 +725,15 @@ static int check_ctrlrecip(struct dev_state *ps, unsigned int requesttype,

		/*
		* check for the special corner case 'get_device_id' in the printer
		* class specification, where wIndex is (interface << 8 \| altsetting)
		* instead of just interface
		* class specification, which we always want to allow as it is used
		* to query things like ink level, etc.
		*/
		if (requesttype == 0xa1 && request == 0) {
		alt_setting = usb_find_alt_setting(ps->dev->actconfig,
		index >> 8, index & 0xff);
		if (alt_setting
		&& alt_setting->desc.bInterfaceClass == USB_CLASS_PRINTER)
		index >>= 8;
		return 0;
		}

		index &= 0xff;