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List:       linux-usb
Subject:    [PATCH V2 2/2] usb: gadget/uvc: Add support for 'USB_GADGET_DELAYED_STATUS' response for a set_intf(
From:       Bhupesh Sharma <bhupesh.sharma () st ! com>
Date:       2012-07-31 0:59:48
Message-ID: 836f95f02232847851a99db1e953eeaaf71b051c.1343695872.git.bhupesh.sharma () st ! com
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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.
So, the application should call the STREAMON on UVC side only when it has
dequeued sufficient buffers from the V4L2 side and queued them to the
UVC gadget.

Signed-off-by: Bhupesh Sharma <bhupesh.sharma@st.com>
---
 drivers/usb/gadget/f_uvc.c    |   16 +++++++++++-----
 drivers/usb/gadget/uvc.h      |    1 +
 drivers/usb/gadget/uvc_v4l2.c |   15 ++++++++++++++-
 3 files changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/usb/gadget/f_uvc.c b/drivers/usb/gadget/f_uvc.c
index 2a8bf06..22f7570 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 +360,12 @@ 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;
+
+		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 93b0c11..9391993 100644
--- a/drivers/usb/gadget/uvc.h
+++ b/drivers/usb/gadget/uvc.h
@@ -190,6 +190,7 @@ 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 134bfe5..b47e0f7 100644
--- a/drivers/usb/gadget/uvc_v4l2.c
+++ b/drivers/usb/gadget/uvc_v4l2.c
@@ -245,7 +245,20 @@ 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);
+		/* enable uvc video. */
+		ret = uvc_video_enable(video, 1);
+		if (ret < 0)
+			return ret;
+
+		/*
+		 * 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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