Sensor orientation reporting

Hi all,

I've finally got round to writing a sample patch to support the proposed mechanism of reporting sensor orientation to user space. It is split into 2 parts, part 1 contains the kernel changes and part 2 the libv4l changes. In order to keep the patch simple I haven't attempted to add support to libv4l for HFLIP and VFLIP but just assumed for now that if a cam needs one then it needs both. If the basic idea gets accepted then fixing that is purely a user space change.

I also haven't provided an implementation of VIDIOC_ENUMINPUT in libv4l that updates the flags to reflect what libv4l has done to the image. Hans Verkuil originally said he wanted to leave the orientation information available to the user app but I suspect that is actually undesirable. If an app is designed to work without libv4l and to re-orient an image as required then if someone runs it with the LD_PRELOAD capability of libv4l then correct operation depends upon reporting the corrected orientation to the app, not the original orientation.

Quoted 6 lines · Adam Baker

Hi all,

I've finally got round to writing a sample patch to support the proposed mechanism of reporting sensor orientation to user space. It is split into 2 parts, part 1 contains the kernel changes and part 2 the libv4l changes. In order to keep the patch simple I haven't attempted to add support to libv4l for HFLIP and VFLIP but just assumed for now that if a cam needs one then it needs both. If the basic idea gets accepted then fixing that is purely a user space change.

I also haven't provided an implementation of VIDIOC_ENUMINPUT in libv4l that updates the flags to reflect what libv4l has done to the image. Hans Verkuil originally said he wanted to leave the orientation information available to the user app but I suspect that is actually undesirable. If an app is designed to work without libv4l and to re-orient an image as required then if someone runs it with the LD_PRELOAD capability of libv4l then correct operation depends upon reporting the corrected orientation to the app, not the original orientation.

Both patches look good to me.

Quoted 1 line · Hans de Goede

Both patches look good to me.

A complaint about lack of documentation wouldn't have gone amiss.

Unfortunately having just remembered that I should have done that I'm struggling to get the current docbook to compile (So far I've suffered Ubuntu not packaging an old enough docbook, missing character set definition files and the Makefile depending on bash but not explicitly requesting it so getting dash).

It looks like it now builds the docs so I'm ready to start updating them.

Adam

Add support to the SQ-905 driver to pass back to user space the sensor orientation information obtained from the camera during init. Modifies gspca and the videodev2.h header to create the necessary API.

Signed-off-by Adam Baker <[email protected]>

---
diff -r 1248509d8bed linux/drivers/media/video/gspca/gspca.c

linux/drivers/media/video/gspca/gspca.c +1 -0

@@ -1147,6 +1147,7 @@ static int vidioc_enum_input(struct file
 	if (input->index != 0)
 		return -EINVAL;
 	input->type = V4L2_INPUT_TYPE_CAMERA;
+	input->status = gspca_dev->input_flags;
 	strncpy(input->name, gspca_dev->sd_desc->name,
 		sizeof input->name);
 	return 0;

diff -r 1248509d8bed linux/drivers/media/video/gspca/gspca.h

linux/drivers/media/video/gspca/gspca.h +1 -0

@@ -168,6 +168,7 @@ struct gspca_dev {
 	__u8 alt;			/* USB alternate setting */
 	__u8 nbalt;			/* number of USB alternate settings */
 	u8 bulk;			/* image transfer by 0:isoc / 1:bulk */
+	u32 input_flags;		/* value for ENUM_INPUT status flags */
 };
 
 int gspca_dev_probe(struct usb_interface *intf,

diff -r 1248509d8bed linux/drivers/media/video/gspca/sq905.c

linux/drivers/media/video/gspca/sq905.c +6 -0

@@ -357,6 +357,12 @@ static int sd_init(struct gspca_dev *gsp
 	gspca_dev->cam.nmodes = ARRAY_SIZE(sq905_mode);
 	if (!(ident & SQ905_HIRES_MASK))
 		gspca_dev->cam.nmodes--;
+
+	if (ident & SQ905_ORIENTATION_MASK)
+		gspca_dev->input_flags = V4L2_IN_ST_VFLIP;
+	else
+		gspca_dev->input_flags = V4L2_IN_ST_VFLIP |
+					 V4L2_IN_ST_HFLIP;
 	return 0;
 }
 

diff -r 1248509d8bed linux/include/linux/videodev2.h

linux/include/linux/videodev2.h +5 -1

@@ -736,6 +736,11 @@ struct v4l2_input {
 #define V4L2_IN_ST_NO_SIGNAL   0x00000002
 #define V4L2_IN_ST_NO_COLOR    0x00000004
 
+/* field 'status' - sensor orientation */
+/* If sensor is mounted upside down set both bits */
+#define V4L2_IN_ST_HFLIP       0x00000010 /* Output is flipped horizontally */
+#define V4L2_IN_ST_VFLIP       0x00000020 /* Output is flipped vertically */
+
 /* field 'status' - analog */
 #define V4L2_IN_ST_NO_H_LOCK   0x00000100  /* No horizontal sync lock */
 #define V4L2_IN_ST_COLOR_KILL  0x00000200  /* Color killer is active */
--

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Add support to the SQ-905 driver to pass back to user space the sensor orientation information obtained from the camera during init. Modifies gspca and the videodev2.h header to create the necessary API.

Signed-off-by Adam Baker <[email protected]>

---

On Sun, 15 Mar 2009 22:29:48 +0000

Quoted 4 lines · Adam Baker

Add support to the SQ-905 driver to pass back to user space the sensor orientation information obtained from the camera during init. Modifies gspca and the videodev2.h header to create the necessary API.

Please provide also the V4L2 specs change to include those new controls.