This patch adds the support in UVC webcam gadget design for providing
USB_GADGET_DELAYED_STATUS in response to a set_interface(alt setting 1) command
issue by the Host.
The current UVC webcam gadget design generates a STREAMON event corresponding
to a set_interface(alt setting 1) command from the Host. This STREAMON event
will eventually be routed to a real V4L2 device.
To start video streaming, it may be required to perform some register writes to
a camera sensor device over slow external busses like I2C or SPI. So, it makes
sense to ensure that we delay the STATUS stage of the
set_interface(alt setting 1) command.
Otherwise, a lot of ISOC IN tokens sent by the Host will be replied to by
zero-length packets by the webcam device. On certain Hosts this may even lead
to ISOC URBs been cancelled from the Host side.
So, as soon as we finish doing all the "streaming" related stuff on the real
V4L2 device, we call a STREAMON ioctl on the UVC side and from here we call the
'usb_composite_setup_continue' function to complete the status stage of the
set_interface(alt setting 1) command.
Further, we need to ensure that we queue no video buffers on the UVC webcam
gadget, until we de-queue a video buffer from the V4L2 device. Also, we need to
enable UVC video related stuff at the first QBUF ioctl call itself,
as the application will call the STREAMON on UVC side only when it has
dequeued sufficient buffers from the V4L2 side and queued them to the UVC
gadget. So, the UVC video enable stuff cannot be done in STREAMON ioctl call.
For the same we add two more UVC states:
- PRE_STREAMING : not even a single buffer has been queued to UVC
- BUF_QUEUED_STREAMING_OFF : one video buffer has been queued to UVC
but we have not yet enabled STREAMING on UVC side.
Signed-off-by: Bhupesh Sharma <bhupesh.sharma@xxxxxx>
---
drivers/usb/gadget/f_uvc.c | 17 ++++++++++++-----
drivers/usb/gadget/uvc.h | 3 +++
drivers/usb/gadget/uvc_v4l2.c | 38 ++++++++++++++++++++++++++++++++++++--
3 files changed, 51 insertions(+), 7 deletions(-)
diff --git a/drivers/usb/gadget/f_uvc.c b/drivers/usb/gadget/f_uvc.c
index 2a8bf06..3589ed0 100644
--- a/drivers/usb/gadget/f_uvc.c
+++ b/drivers/usb/gadget/f_uvc.c
@@ -272,6 +272,13 @@ uvc_function_setup(struct usb_function *f, const struct usb_ctrlrequest *ctrl)
return 0;
}
+void uvc_function_setup_continue(struct uvc_device *uvc)
+{
+ struct usb_composite_dev *cdev = uvc->func.config->cdev;
+
+ usb_composite_setup_continue(cdev);
+}
+
static int
uvc_function_get_alt(struct usb_function *f, unsigned interface)
{
@@ -334,7 +341,8 @@ uvc_function_set_alt(struct usb_function *f, unsigned interface, unsigned alt)
v4l2_event_queue(uvc->vdev, &v4l2_event);
uvc->state = UVC_STATE_CONNECTED;
- break;
+
+ return 0;
case 1:
if (uvc->state != UVC_STATE_CONNECTED)
@@ -352,14 +360,13 @@ uvc_function_set_alt(struct usb_function *f, unsigned interface, unsigned alt)
v4l2_event.type = UVC_EVENT_STREAMON;
v4l2_event_queue(uvc->vdev, &v4l2_event);
- uvc->state = UVC_STATE_STREAMING;
- break;
+ uvc->state = UVC_STATE_PRE_STREAMING;
+
+ return USB_GADGET_DELAYED_STATUS;
default:
return -EINVAL;
}
-
- return 0;
}
static void
diff --git a/drivers/usb/gadget/uvc.h b/drivers/usb/gadget/uvc.h
index d78ea25..6cd1435 100644
--- a/drivers/usb/gadget/uvc.h
+++ b/drivers/usb/gadget/uvc.h
@@ -141,6 +141,8 @@ enum uvc_state
{
UVC_STATE_DISCONNECTED,
UVC_STATE_CONNECTED,
+ UVC_STATE_PRE_STREAMING,
+ UVC_STATE_BUF_QUEUED_STREAMING_OFF,
UVC_STATE_STREAMING,
};
@@ -190,6 +192,7 @@ struct uvc_file_handle
* Functions
*/
+extern void uvc_function_setup_continue(struct uvc_device *uvc);
extern void uvc_endpoint_stream(struct uvc_device *dev);
extern void uvc_function_connect(struct uvc_device *uvc);
diff --git a/drivers/usb/gadget/uvc_v4l2.c b/drivers/usb/gadget/uvc_v4l2.c
index 9c2b45b..5f23571 100644
--- a/drivers/usb/gadget/uvc_v4l2.c
+++ b/drivers/usb/gadget/uvc_v4l2.c
@@ -235,10 +235,36 @@ uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)
}
case VIDIOC_QBUF:
+ /*
+ * Theory of operation:
+ * - for the very first QBUF call the uvc state will be
+ * UVC_STATE_PRE_STREAMING, so we need to initialize
+ * the UVC video pipe (allocate requests, init queue,
+ * ..) and change the uvc state to
+ * UVC_STATE_BUF_QUEUED_STREAMING_OFF.
+ *
+ * - For the QBUF calls thereafter, (until STREAMON is
+ * called) we just need to queue the buffers.
+ *
+ * - Once STREAMON has been called (which is handled by the
+ * STREAMON case below), we need to start pumping the data
+ * to USB side here itself.
+ */
if ((ret = uvc_queue_buffer(&video->queue, arg)) < 0)
return ret;
- return uvc_video_pump(video);
+ if (uvc->state == UVC_STATE_PRE_STREAMING) {
+ ret = uvc_video_enable(video, 1);
+ if (ret < 0)
+ return ret;
+
+ uvc->state = UVC_STATE_BUF_QUEUED_STREAMING_OFF;
+ return 0;
+ } else if (uvc->state == UVC_STATE_STREAMING) {
+ return uvc_video_pump(video);
+ } else {
+ return 0;
+ }
case VIDIOC_DQBUF:
return uvc_dequeue_buffer(&video->queue, arg,
@@ -251,7 +277,15 @@ uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)
if (*type != video->queue.queue.type)
return -EINVAL;
- return uvc_video_enable(video, 1);
+ /*
+ * since the real video device has now started streaming
+ * its safe now to complete the status phase of the
+ * set_interface (alt setting 1)
+ */
+ uvc_function_setup_continue(uvc);
+ uvc->state = UVC_STATE_STREAMING;
+
+ return 0;
}
case VIDIOC_STREAMOFF:
--
1.7.2.2
--
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