[PATCH v8 3/3] uvcvideo: handle control pipe protocol STALLs

Guennadi Liakhovetski
2018-05-08T15:07:48Z

When a command ends up in a STALL on the control pipe, use the Request
Error Code control to provide a more precise error information to the
user. For example, if a camera is still busy processing a control,
when the same or an interrelated control set request arrives, the
camera can react with a STALL and then return the "Not ready" status
in response to a UVC_VC_REQUEST_ERROR_CODE_CONTROL command. With this
patch the user would then get an EBUSY error code instead of a
generic EPIPE.

Signed-off-by: Guennadi Liakhovetski <guennadi.liakhovetski@intel.com>
---

v8:

* restrict UVC_VC_REQUEST_ERROR_CODE_CONTROL to the control interface
* fix the wIndex value
* improve error codes
* cosmetic changes

drivers/media/usb/uvc/uvc_video.c | 52 ++++++++++++++++++++++++++++++++++-----
1 file changed, 46 insertions(+), 6 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index aa0082f..ce65cd6 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -73,17 +73,57 @@ int uvc_query_ctrl(struct uvc_device *dev, u8 query, u8 unit,
u8 intfnum, u8 cs, void *data, u16 size)
{
int ret;
+ u8 error;
+ u8 tmp;

ret = __uvc_query_ctrl(dev, query, unit, intfnum, cs, data, size,
UVC_CTRL_CONTROL_TIMEOUT);
- if (ret != size) {
- uvc_printk(KERN_ERR, "Failed to query (%s) UVC control %u on "
- "unit %u: %d (exp. %u).\n", uvc_query_name(query), cs,
- unit, ret, size);
- return -EIO;
+ if (likely(ret == size))
+ return 0;
+
+ uvc_printk(KERN_ERR,
+ "Failed to query (%s) UVC control %u on unit %u: %d (exp. %u).\n",
+ uvc_query_name(query), cs, unit, ret, size);
+
+ if (ret != -EPIPE)
+ return ret;
+
+ tmp = *(u8 *)data;
+
+ ret = __uvc_query_ctrl(dev, UVC_GET_CUR, 0, intfnum,
+ UVC_VC_REQUEST_ERROR_CODE_CONTROL, data, 1,
+ UVC_CTRL_CONTROL_TIMEOUT);
+
+ error = *(u8 *)data;
+ *(u8 *)data = tmp;
+
+ if (ret != 1)
+ return ret < 0 ? ret : -EPIPE;
+
+ uvc_trace(UVC_TRACE_CONTROL, "Control error %u\n", error);
+
+ switch (error) {
+ case 0:
+ /* Cannot happen - we received a STALL */
+ return -EPIPE;
+ case 1: /* Not ready */
+ return -EBUSY;
+ case 2: /* Wrong state */
+ return -EILSEQ;
+ case 3: /* Power */
+ return -EREMOTE;
+ case 4: /* Out of range */
+ return -ERANGE;
+ case 5: /* Invalid unit */
+ case 6: /* Invalid control */
+ case 7: /* Invalid Request */
+ case 8: /* Invalid value within range */
+ return -EINVAL;
+ default: /* reserved or unknown */
+ break;
}

- return 0;
+ return -EPIPE;
}

static void uvc_fixup_video_ctrl(struct uvc_streaming *stream,
--
1.9.3