V4L/DVB (12534): soc-camera: V4L2 API compliant scaling (S_FMT) and c…

…ropping (S_CROP)

The initial soc-camera scaling and cropping implementation turned out to be
incompliant with the V4L2 API, e.g., it expected the user to specify cropping
in output window pixels, instead of input window pixels. This patch converts
the soc-camera core and all drivers to comply with the standard.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

Documentation/video4linux/soc-camera.txt

@@ -116,5 +116,45 @@ functionality.
 struct soc_camera_device also links to an array of struct soc_camera_data_format,
 listing pixel formats, supported by the camera.
 
+VIDIOC_S_CROP and VIDIOC_S_FMT behaviour
+----------------------------------------
+
+Above user ioctls modify image geometry as follows:
+
+VIDIOC_S_CROP: sets location and sizes of the sensor window. Unit is one sensor
+pixel. Changing sensor window sizes preserves any scaling factors, therefore
+user window sizes change as well.
+
+VIDIOC_S_FMT: sets user window. Should preserve previously set sensor window as
+much as possible by modifying scaling factors. If the sensor window cannot be
+preserved precisely, it may be changed too.
+
+In soc-camera there are two locations, where scaling and cropping can taks
+place: in the camera driver and in the host driver. User ioctls are first passed
+to the host driver, which then generally passes them down to the camera driver.
+It is more efficient to perform scaling and cropping in the camera driver to
+save camera bus bandwidth and maximise the framerate. However, if the camera
+driver failed to set the required parameters with sufficient precision, the host
+driver may decide to also use its own scaling and cropping to fulfill the user's
+request.
+
+Camera drivers are interfaced to the soc-camera core and to host drivers over
+the v4l2-subdev API, which is completely functional, it doesn't pass any data.
+Therefore all camera drivers shall reply to .g_fmt() requests with their current
+output geometry. This is necessary to correctly configure the camera bus.
+.s_fmt() and .try_fmt() have to be implemented too. Sensor window and scaling
+factors have to be maintained by camera drivers internally. According to the
+V4L2 API all capture drivers must support the VIDIOC_CROPCAP ioctl, hence we
+rely on camera drivers implementing .cropcap(). If the camera driver does not
+support cropping, it may choose to not implement .s_crop(), but to enable
+cropping support by the camera host driver at least the .g_crop method must be
+implemented.
+
+User window geometry is kept in .user_width and .user_height fields in struct
+soc_camera_device and used by the soc-camera core and host drivers. The core
+updates these fields upon successful completion of a .s_fmt() call, but if these
+fields change elsewhere, e.g., during .s_crop() processing, the host driver is
+responsible for updating them.
+
 --
 Author: Guennadi Liakhovetski <g.liakhovetski@gmx.de>

drivers/media/video/mt9m001.c

@@ -39,6 +39,13 @@
 #define MT9M001_GLOBAL_GAIN		0x35
 #define MT9M001_CHIP_ENABLE		0xF1
 
+#define MT9M001_MAX_WIDTH		1280
+#define MT9M001_MAX_HEIGHT		1024
+#define MT9M001_MIN_WIDTH		48
+#define MT9M001_MIN_HEIGHT		32
+#define MT9M001_COLUMN_SKIP		20
+#define MT9M001_ROW_SKIP		12
+
 static const struct soc_camera_data_format mt9m001_colour_formats[] = {
 	/* Order important: first natively supported,
 	 * second supported with a GPIO extender */
@@ -70,6 +77,8 @@ static const struct soc_camera_data_format mt9m001_monochrome_formats[] = {
 
 struct mt9m001 {
 	struct v4l2_subdev subdev;
+	struct v4l2_rect rect;	/* Sensor window */
+	__u32 fourcc;
 	int model;	/* V4L2_IDENT_MT9M001* codes from v4l2-chip-ident.h */
 	unsigned char autoexposure;
 };
@@ -196,13 +205,31 @@ static unsigned long mt9m001_query_bus_param(struct soc_camera_device *icd)
 
 static int mt9m001_s_crop(struct v4l2_subdev *sd, struct v4l2_crop *a)
 {
-	struct v4l2_rect *rect = &a->c;
 	struct i2c_client *client = sd->priv;
 	struct mt9m001 *mt9m001 = to_mt9m001(client);
+	struct v4l2_rect rect = a->c;
 	struct soc_camera_device *icd = client->dev.platform_data;
 	int ret;
 	const u16 hblank = 9, vblank = 25;
 
+	if (mt9m001->fourcc == V4L2_PIX_FMT_SBGGR8 ||
+	    mt9m001->fourcc == V4L2_PIX_FMT_SBGGR16)
+		/*
+		 * Bayer format - even number of rows for simplicity,
+		 * but let the user play with the top row.
+		 */
+		rect.height = ALIGN(rect.height, 2);
+
+	/* Datasheet requirement: see register description */
+	rect.width = ALIGN(rect.width, 2);
+	rect.left = ALIGN(rect.left, 2);
+
+	soc_camera_limit_side(&rect.left, &rect.width,
+		     MT9M001_COLUMN_SKIP, MT9M001_MIN_WIDTH, MT9M001_MAX_WIDTH);
+
+	soc_camera_limit_side(&rect.top, &rect.height,
+		     MT9M001_ROW_SKIP, MT9M001_MIN_HEIGHT, MT9M001_MAX_HEIGHT);
+
 	/* Blanking and start values - default... */
 	ret = reg_write(client, MT9M001_HORIZONTAL_BLANKING, hblank);
 	if (!ret)
@@ -211,46 +238,98 @@ static int mt9m001_s_crop(struct v4l2_subdev *sd, struct v4l2_crop *a)
 	/* The caller provides a supported format, as verified per
 	 * call to icd->try_fmt() */
 	if (!ret)
-		ret = reg_write(client, MT9M001_COLUMN_START, rect->left);
+		ret = reg_write(client, MT9M001_COLUMN_START, rect.left);
 	if (!ret)
-		ret = reg_write(client, MT9M001_ROW_START, rect->top);
+		ret = reg_write(client, MT9M001_ROW_START, rect.top);
 	if (!ret)
-		ret = reg_write(client, MT9M001_WINDOW_WIDTH, rect->width - 1);
+		ret = reg_write(client, MT9M001_WINDOW_WIDTH, rect.width - 1);
 	if (!ret)
 		ret = reg_write(client, MT9M001_WINDOW_HEIGHT,
-				rect->height + icd->y_skip_top - 1);
+				rect.height + icd->y_skip_top - 1);
 	if (!ret && mt9m001->autoexposure) {
 		ret = reg_write(client, MT9M001_SHUTTER_WIDTH,
-				rect->height + icd->y_skip_top + vblank);
+				rect.height + icd->y_skip_top + vblank);
 		if (!ret) {
 			const struct v4l2_queryctrl *qctrl =
 				soc_camera_find_qctrl(icd->ops,
 						      V4L2_CID_EXPOSURE);
-			icd->exposure = (524 + (rect->height + icd->y_skip_top +
+			icd->exposure = (524 + (rect.height + icd->y_skip_top +
 						vblank - 1) *
 					 (qctrl->maximum - qctrl->minimum)) /
 				1048 + qctrl->minimum;
 		}
 	}
 
+	if (!ret)
+		mt9m001->rect = rect;
+
 	return ret;
 }
 
+static int mt9m001_g_crop(struct v4l2_subdev *sd, struct v4l2_crop *a)
+{
+	struct i2c_client *client = sd->priv;
+	struct mt9m001 *mt9m001 = to_mt9m001(client);
+
+	a->c	= mt9m001->rect;
+	a->type	= V4L2_BUF_TYPE_VIDEO_CAPTURE;
+
+	return 0;
+}
+
+static int mt9m001_cropcap(struct v4l2_subdev *sd, struct v4l2_cropcap *a)
+{
+	a->bounds.left			= MT9M001_COLUMN_SKIP;
+	a->bounds.top			= MT9M001_ROW_SKIP;
+	a->bounds.width			= MT9M001_MAX_WIDTH;
+	a->bounds.height		= MT9M001_MAX_HEIGHT;
+	a->defrect			= a->bounds;
+	a->type				= V4L2_BUF_TYPE_VIDEO_CAPTURE;
+	a->pixelaspect.numerator	= 1;
+	a->pixelaspect.denominator	= 1;
+
+	return 0;
+}
+
+static int mt9m001_g_fmt(struct v4l2_subdev *sd, struct v4l2_format *f)
+{
+	struct i2c_client *client = sd->priv;
+	struct mt9m001 *mt9m001 = to_mt9m001(client);
+	struct v4l2_pix_format *pix = &f->fmt.pix;
+
+	pix->width		= mt9m001->rect.width;
+	pix->height		= mt9m001->rect.height;
+	pix->pixelformat	= mt9m001->fourcc;
+	pix->field		= V4L2_FIELD_NONE;
+	pix->colorspace		= V4L2_COLORSPACE_SRGB;
+
+	return 0;
+}
+
 static int mt9m001_s_fmt(struct v4l2_subdev *sd, struct v4l2_format *f)
 {
 	struct i2c_client *client = sd->priv;
-	struct soc_camera_device *icd = client->dev.platform_data;
+	struct mt9m001 *mt9m001 = to_mt9m001(client);
+	struct v4l2_pix_format *pix = &f->fmt.pix;
 	struct v4l2_crop a = {
 		.c = {
-			.left	= icd->rect_current.left,
-			.top	= icd->rect_current.top,
-			.width	= f->fmt.pix.width,
-			.height	= f->fmt.pix.height,
+			.left	= mt9m001->rect.left,
+			.top	= mt9m001->rect.top,
+			.width	= pix->width,
+			.height	= pix->height,
 		},
 	};
+	int ret;
 
 	/* No support for scaling so far, just crop. TODO: use skipping */
-	return mt9m001_s_crop(sd, &a);
+	ret = mt9m001_s_crop(sd, &a);
+	if (!ret) {
+		pix->width = mt9m001->rect.width;
+		pix->height = mt9m001->rect.height;
+		mt9m001->fourcc = pix->pixelformat;
+	}
+
+	return ret;
 }
 
 static int mt9m001_try_fmt(struct v4l2_subdev *sd, struct v4l2_format *f)
@@ -259,9 +338,14 @@ static int mt9m001_try_fmt(struct v4l2_subdev *sd, struct v4l2_format *f)
 	struct soc_camera_device *icd = client->dev.platform_data;
 	struct v4l2_pix_format *pix = &f->fmt.pix;
 
-	v4l_bound_align_image(&pix->width, 48, 1280, 1,
-			      &pix->height, 32 + icd->y_skip_top,
-			      1024 + icd->y_skip_top, 0, 0);
+	v4l_bound_align_image(&pix->width, MT9M001_MIN_WIDTH,
+		MT9M001_MAX_WIDTH, 1,
+		&pix->height, MT9M001_MIN_HEIGHT + icd->y_skip_top,
+		MT9M001_MAX_HEIGHT + icd->y_skip_top, 0, 0);
+
+	if (pix->pixelformat == V4L2_PIX_FMT_SBGGR8 ||
+	    pix->pixelformat == V4L2_PIX_FMT_SBGGR16)
+		pix->height = ALIGN(pix->height - 1, 2);
 
 	return 0;
 }
@@ -472,11 +556,11 @@ static int mt9m001_s_ctrl(struct v4l2_subdev *sd, struct v4l2_control *ctrl)
 		if (ctrl->value) {
 			const u16 vblank = 25;
 			if (reg_write(client, MT9M001_SHUTTER_WIDTH,
-				      icd->rect_current.height +
+				      mt9m001->rect.height +
 				      icd->y_skip_top + vblank) < 0)
 				return -EIO;
 			qctrl = soc_camera_find_qctrl(icd->ops, V4L2_CID_EXPOSURE);
-			icd->exposure = (524 + (icd->rect_current.height +
+			icd->exposure = (524 + (mt9m001->rect.height +
 						icd->y_skip_top + vblank - 1) *
 					 (qctrl->maximum - qctrl->minimum)) /
 				1048 + qctrl->minimum;
@@ -548,6 +632,8 @@ static int mt9m001_video_probe(struct soc_camera_device *icd,
 	if (flags & SOCAM_DATAWIDTH_8)
 		icd->num_formats++;
 
+	mt9m001->fourcc = icd->formats->fourcc;
+
 	dev_info(&client->dev, "Detected a MT9M001 chip ID %x (%s)\n", data,
 		 data == 0x8431 ? "C12STM" : "C12ST");
 
@@ -556,10 +642,9 @@ static int mt9m001_video_probe(struct soc_camera_device *icd,
 
 static void mt9m001_video_remove(struct soc_camera_device *icd)
 {
-	struct i2c_client *client = to_i2c_client(to_soc_camera_control(icd));
 	struct soc_camera_link *icl = to_soc_camera_link(icd);
 
-	dev_dbg(&client->dev, "Video %x removed: %p, %p\n", client->addr,
+	dev_dbg(&icd->dev, "Video removed: %p, %p\n",
 		icd->dev.parent, icd->vdev);
 	if (icl->free_bus)
 		icl->free_bus(icl);
@@ -578,8 +663,11 @@ static struct v4l2_subdev_core_ops mt9m001_subdev_core_ops = {
 static struct v4l2_subdev_video_ops mt9m001_subdev_video_ops = {
 	.s_stream	= mt9m001_s_stream,
 	.s_fmt		= mt9m001_s_fmt,
+	.g_fmt		= mt9m001_g_fmt,
 	.try_fmt	= mt9m001_try_fmt,
 	.s_crop		= mt9m001_s_crop,
+	.g_crop		= mt9m001_g_crop,
+	.cropcap	= mt9m001_cropcap,
 };
 
 static struct v4l2_subdev_ops mt9m001_subdev_ops = {
@@ -621,15 +709,13 @@ static int mt9m001_probe(struct i2c_client *client,
 
 	/* Second stage probe - when a capture adapter is there */
 	icd->ops		= &mt9m001_ops;
-	icd->rect_max.left	= 20;
-	icd->rect_max.top	= 12;
-	icd->rect_max.width	= 1280;
-	icd->rect_max.height	= 1024;
-	icd->rect_current.left	= 20;
-	icd->rect_current.top	= 12;
-	icd->width_min		= 48;
-	icd->height_min		= 32;
 	icd->y_skip_top		= 1;
+
+	mt9m001->rect.left	= MT9M001_COLUMN_SKIP;
+	mt9m001->rect.top	= MT9M001_ROW_SKIP;
+	mt9m001->rect.width	= MT9M001_MAX_WIDTH;
+	mt9m001->rect.height	= MT9M001_MAX_HEIGHT;
+
 	/* Simulated autoexposure. If enabled, we calculate shutter width
 	 * ourselves in the driver based on vertical blanking and frame width */
 	mt9m001->autoexposure = 1;