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@xxxxxx>
CC: Alan Stern <stern@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Hans de Goede <hdegoede@xxxxxxxxxx>
---
drivers/usb/core/devio.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index c88c4fb..6beeb6d 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -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;
--
1.8.3.1
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