[media] V4L2: soc-camera: move generic functions into a separate file

The sh_mobile_ceu_camera driver implements a generic algorithm for setting
up an optimal client and host scaling and cropping configuration. This
patch makes those functions available for all drivers.

Signed-off-by: Guennadi Liakhovetski <[e-mail]>
Signed-off-by: Mauro Carvalho Chehab <[e-mail]>

drivers/media/platform/soc_camera/Kconfig

···
 	  over a bus like PCI or USB. For example some i2c camera connected
 	  directly to the data bus of an SoC.
 
+config SOC_CAMERA_SCALE_CROP
+	tristate
+
 config SOC_CAMERA_PLATFORM
 	tristate "platform camera support"
 	depends on SOC_CAMERA
···
 	tristate "SuperH Mobile CEU Interface driver"
 	depends on VIDEO_DEV && SOC_CAMERA && HAS_DMA && HAVE_CLK
 	select VIDEOBUF2_DMA_CONTIG
+	select SOC_CAMERA_SCALE_CROP
 	---help---
 	  This is a v4l2 driver for the SuperH Mobile CEU Interface
 

drivers/media/platform/soc_camera/Makefile

···
 obj-$(CONFIG_SOC_CAMERA)		+= soc_camera.o soc_mediabus.o
+obj-$(CONFIG_SOC_CAMERA_SCALE_CROP)	+= soc_scale_crop.o
+
+# a platform subdevice driver stub, allowing to support cameras by adding a
+# couple of callback functions to the board code
 obj-$(CONFIG_SOC_CAMERA_PLATFORM)	+= soc_camera_platform.o
 
 # soc-camera host drivers have to be linked after camera drivers

drivers/media/platform/soc_camera/sh_mobile_ceu_camera.c

···
 #include <media/v4l2-mediabus.h>
 #include <media/soc_mediabus.h>
 
+#include "soc_scale_crop.h"
+
 /* register offsets for sh7722 / sh7723 */
 
 #define CAPSR  0x00 /* Capture start register */
···
 		 fmt->packing == SOC_MBUS_PACKING_EXTEND16);
 }
 
-static int soc_camera_client_g_rect(struct v4l2_subdev *sd, struct v4l2_rect *rect);
-
 static struct soc_camera_device *ctrl_to_icd(struct v4l2_ctrl *ctrl)
 {
 	return container_of(ctrl->handler, struct soc_camera_device,
···
 	icd->host_priv = NULL;
 }
 
-/* Check if any dimension of r1 is smaller than respective one of r2 */
-static bool is_smaller(const struct v4l2_rect *r1, const struct v4l2_rect *r2)
-{
-	return r1->width < r2->width || r1->height < r2->height;
-}
-
-/* Check if r1 fails to cover r2 */
-static bool is_inside(const struct v4l2_rect *r1, const struct v4l2_rect *r2)
-{
-	return r1->left > r2->left || r1->top > r2->top ||
-		r1->left + r1->width < r2->left + r2->width ||
-		r1->top + r1->height < r2->top + r2->height;
-}
-
-static unsigned int soc_camera_shift_scale(unsigned int size, unsigned int shift,
-					   unsigned int scale)
-{
-	return ((size << shift) + scale / 2) / scale;
-}
-
-static unsigned int soc_camera_calc_scale(unsigned int input, unsigned int shift,
-					  unsigned int output)
-{
-	return soc_camera_shift_scale(input, shift, output);
-}
-
 #define scale_down(size, scale) soc_camera_shift_scale(size, 12, scale)
-#define calc_generic_scale(in, out) soc_camera_shift_scale(in, 12, out)
-
-/* Get and store current client crop */
-static int soc_camera_client_g_rect(struct v4l2_subdev *sd, struct v4l2_rect *rect)
-{
-	struct v4l2_crop crop;
-	struct v4l2_cropcap cap;
-	int ret;
-
-	crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-
-	ret = v4l2_subdev_call(sd, video, g_crop, &crop);
-	if (!ret) {
-		*rect = crop.c;
-		return ret;
-	}
-
-	/* Camera driver doesn't support .g_crop(), assume default rectangle */
-	cap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-
-	ret = v4l2_subdev_call(sd, video, cropcap, &cap);
-	if (!ret)
-		*rect = cap.defrect;
-
-	return ret;
-}
-
-/* Client crop has changed, update our sub-rectangle to remain within the area */
-static void update_subrect(struct v4l2_rect *rect, struct v4l2_rect *subrect)
-{
-	if (rect->width < subrect->width)
-		subrect->width = rect->width;
-
-	if (rect->height < subrect->height)
-		subrect->height = rect->height;
-
-	if (rect->left > subrect->left)
-		subrect->left = rect->left;
-	else if (rect->left + rect->width >
-		 subrect->left + subrect->width)
-		subrect->left = rect->left + rect->width -
-			subrect->width;
-
-	if (rect->top > subrect->top)
-		subrect->top = rect->top;
-	else if (rect->top + rect->height >
-		 subrect->top + subrect->height)
-		subrect->top = rect->top + rect->height -
-			subrect->height;
-}
-
-/*
- * The common for both scaling and cropping iterative approach is:
- * 1. try if the client can produce exactly what requested by the user
- * 2. if (1) failed, try to double the client image until we get one big enough
- * 3. if (2) failed, try to request the maximum image
- */
-static int soc_camera_client_s_crop(struct v4l2_subdev *sd,
-			struct v4l2_crop *crop, struct v4l2_crop *cam_crop,
-			struct v4l2_rect *target_rect, struct v4l2_rect *subrect)
-{
-	struct v4l2_rect *rect = &crop->c, *cam_rect = &cam_crop->c;
-	struct device *dev = sd->v4l2_dev->dev;
-	struct v4l2_cropcap cap;
-	int ret;
-	unsigned int width, height;
-
-	v4l2_subdev_call(sd, video, s_crop, crop);
-	ret = soc_camera_client_g_rect(sd, cam_rect);
-	if (ret < 0)
-		return ret;
-
-	/*
-	 * Now cam_crop contains the current camera input rectangle, and it must
-	 * be within camera cropcap bounds
-	 */
-	if (!memcmp(rect, cam_rect, sizeof(*rect))) {
-		/* Even if camera S_CROP failed, but camera rectangle matches */
-		dev_dbg(dev, "Camera S_CROP successful for %dx%d@%d:%d\n",
-			rect->width, rect->height, rect->left, rect->top);
-		*target_rect = *cam_rect;
-		return 0;
-	}
-
-	/* Try to fix cropping, that camera hasn't managed to set */
-	dev_geo(dev, "Fix camera S_CROP for %dx%d@%d:%d to %dx%d@%d:%d\n",
-		cam_rect->width, cam_rect->height,
-		cam_rect->left, cam_rect->top,
-		rect->width, rect->height, rect->left, rect->top);
-
-	/* We need sensor maximum rectangle */
-	ret = v4l2_subdev_call(sd, video, cropcap, &cap);
-	if (ret < 0)
-		return ret;
-
-	/* Put user requested rectangle within sensor bounds */
-	soc_camera_limit_side(&rect->left, &rect->width, cap.bounds.left, 2,
-			      cap.bounds.width);
-	soc_camera_limit_side(&rect->top, &rect->height, cap.bounds.top, 4,
-			      cap.bounds.height);
-
-	/*
-	 * Popular special case - some cameras can only handle fixed sizes like
-	 * QVGA, VGA,... Take care to avoid infinite loop.
-	 */
-	width = max(cam_rect->width, 2);
-	height = max(cam_rect->height, 2);
-
-	/*
-	 * Loop as long as sensor is not covering the requested rectangle and
-	 * is still within its bounds
-	 */
-	while (!ret && (is_smaller(cam_rect, rect) ||
-			is_inside(cam_rect, rect)) &&
-	       (cap.bounds.width > width || cap.bounds.height > height)) {
-
-		width *= 2;
-		height *= 2;
-
-		cam_rect->width = width;
-		cam_rect->height = height;
-
-		/*
-		 * We do not know what capabilities the camera has to set up
-		 * left and top borders. We could try to be smarter in iterating
-		 * them, e.g., if camera current left is to the right of the
-		 * target left, set it to the middle point between the current
-		 * left and minimum left. But that would add too much
-		 * complexity: we would have to iterate each border separately.
-		 * Instead we just drop to the left and top bounds.
-		 */
-		if (cam_rect->left > rect->left)
-			cam_rect->left = cap.bounds.left;
-
-		if (cam_rect->left + cam_rect->width < rect->left + rect->width)
-			cam_rect->width = rect->left + rect->width -
-				cam_rect->left;
-
-		if (cam_rect->top > rect->top)
-			cam_rect->top = cap.bounds.top;
-
-		if (cam_rect->top + cam_rect->height < rect->top + rect->height)
-			cam_rect->height = rect->top + rect->height -
-				cam_rect->top;
-
-		v4l2_subdev_call(sd, video, s_crop, cam_crop);
-		ret = soc_camera_client_g_rect(sd, cam_rect);
-		dev_geo(dev, "Camera S_CROP %d for %dx%d@%d:%d\n", ret,
-			cam_rect->width, cam_rect->height,
-			cam_rect->left, cam_rect->top);
-	}
-
-	/* S_CROP must not modify the rectangle */
-	if (is_smaller(cam_rect, rect) || is_inside(cam_rect, rect)) {
-		/*
-		 * The camera failed to configure a suitable cropping,
-		 * we cannot use the current rectangle, set to max
-		 */
-		*cam_rect = cap.bounds;
-		v4l2_subdev_call(sd, video, s_crop, cam_crop);
-		ret = soc_camera_client_g_rect(sd, cam_rect);
-		dev_geo(dev, "Camera S_CROP %d for max %dx%d@%d:%d\n", ret,
-			cam_rect->width, cam_rect->height,
-			cam_rect->left, cam_rect->top);
-	}
-
-	if (!ret) {
-		*target_rect = *cam_rect;
-		update_subrect(target_rect, subrect);
-	}
-
-	return ret;
-}
-
-/* Iterative s_mbus_fmt, also updates cached client crop on success */
-static int client_s_fmt(struct soc_camera_device *icd,
-			struct v4l2_rect *rect, struct v4l2_rect *subrect,
-			unsigned int max_width, unsigned int max_height,
-			struct v4l2_mbus_framefmt *mf, bool host_can_scale)
-{
-	struct v4l2_subdev *sd = soc_camera_to_subdev(icd);
-	struct device *dev = icd->parent;
-	unsigned int width = mf->width, height = mf->height, tmp_w, tmp_h;
-	struct v4l2_cropcap cap;
-	bool ceu_1to1;
-	int ret;
-
-	ret = v4l2_device_call_until_err(sd->v4l2_dev,
-					 soc_camera_grp_id(icd), video,
-					 s_mbus_fmt, mf);
-	if (ret < 0)
-		return ret;
-
-	dev_geo(dev, "camera scaled to %ux%u\n", mf->width, mf->height);
-
-	if (width == mf->width && height == mf->height) {
-		/* Perfect! The client has done it all. */
-		ceu_1to1 = true;
-		goto update_cache;
-	}
-
-	ceu_1to1 = false;
-	if (!host_can_scale)
-		goto update_cache;
-
-	cap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
-
-	ret = v4l2_subdev_call(sd, video, cropcap, &cap);
-	if (ret < 0)
-		return ret;
-
-	if (max_width > cap.bounds.width)
-		max_width = cap.bounds.width;
-	if (max_height > cap.bounds.height)
-		max_height = cap.bounds.height;
-
-	/* Camera set a format, but geometry is not precise, try to improve */
-	tmp_w = mf->width;
-	tmp_h = mf->height;
-
-	/* width <= max_width && height <= max_height - guaranteed by try_fmt */
-	while ((width > tmp_w || height > tmp_h) &&
-	       tmp_w < max_width && tmp_h < max_height) {
-		tmp_w = min(2 * tmp_w, max_width);
-		tmp_h = min(2 * tmp_h, max_height);
-		mf->width = tmp_w;
-		mf->height = tmp_h;
-		ret = v4l2_device_call_until_err(sd->v4l2_dev,
-					soc_camera_grp_id(icd), video,
-					s_mbus_fmt, mf);
-		dev_geo(dev, "Camera scaled to %ux%u\n",
-			mf->width, mf->height);
-		if (ret < 0) {
-			/* This shouldn't happen */
-			dev_err(dev, "Client failed to set format: %d\n", ret);
-			return ret;
-		}
-	}
-
-update_cache:
-	/* Update cache */
-	ret = soc_camera_client_g_rect(sd, rect);
-	if (ret < 0)
-		return ret;
-
-	if (ceu_1to1)
-		*subrect = *rect;
-	else
-		update_subrect(rect, subrect);
-
-	return 0;
-}
-
-/**
- * @icd		- soc-camera device
- * @rect	- camera cropping window
- * @subrect	- part of rect, sent to the user
- * @mf		- in- / output camera output window
- * @width	- on input: max host input width
- *		  on output: user width, mapped back to input
- * @height	- on input: max host input height
- *		  on output: user height, mapped back to input
- * @host_can_scale - host can scale this pixel format
- * @shift	- shift, used for scaling
- */
-static int soc_camera_client_scale(struct soc_camera_device *icd,
-			struct v4l2_rect *rect, struct v4l2_rect *subrect,
-			struct v4l2_mbus_framefmt *mf,
-			unsigned int *width, unsigned int *height,
-			bool host_can_scale, unsigned int shift)
-{
-	struct device *dev = icd->parent;
-	struct v4l2_mbus_framefmt mf_tmp = *mf;
-	unsigned int scale_h, scale_v;
-	int ret;
-
-	/*
-	 * 5. Apply iterative camera S_FMT for camera user window (also updates
-	 *    client crop cache and the imaginary sub-rectangle).
-	 */
-	ret = client_s_fmt(icd, rect, subrect, *width, *height,
-			   &mf_tmp, host_can_scale);
-	if (ret < 0)
-		return ret;
-
-	dev_geo(dev, "5: camera scaled to %ux%u\n",
-		mf_tmp.width, mf_tmp.height);
-
-	/* 6. Retrieve camera output window (g_fmt) */
-
-	/* unneeded - it is already in "mf_tmp" */
-
-	/* 7. Calculate new client scales. */
-	scale_h = soc_camera_calc_scale(rect->width, shift, mf_tmp.width);
-	scale_v = soc_camera_calc_scale(rect->height, shift, mf_tmp.height);
-
-	mf->width	= mf_tmp.width;
-	mf->height	= mf_tmp.height;
-	mf->colorspace	= mf_tmp.colorspace;
-
-	/*
-	 * 8. Calculate new CEU crop - apply camera scales to previously
-	 *    updated "effective" crop.
-	 */
-	*width = soc_camera_shift_scale(subrect->width, shift, scale_h);
-	*height = soc_camera_shift_scale(subrect->height, shift, scale_v);
-
-	dev_geo(dev, "8: new client sub-window %ux%u\n", *width, *height);
-
-	return 0;
-}
+#define calc_generic_scale(in, out) soc_camera_calc_scale(in, 12, out)
 
 /*
  * CEU can scale and crop, but we don't want to waste bandwidth and kill the
···
 	a->c = cam->subrect;
 
 	return 0;
-}
-
-/*
- * Calculate real client output window by applying new scales to the current
- * client crop. New scales are calculated from the requested output format and
- * CEU crop, mapped backed onto the client input (subrect).
- */
-static void soc_camera_calc_client_output(struct soc_camera_device *icd,
-		struct v4l2_rect *rect, struct v4l2_rect *subrect,
-		const struct v4l2_pix_format *pix, struct v4l2_mbus_framefmt *mf,
-		unsigned int shift)
-{
-	struct device *dev = icd->parent;
-	unsigned int scale_v, scale_h;
-
-	if (subrect->width == rect->width &&
-	    subrect->height == rect->height) {
-		/* No sub-cropping */
-		mf->width	= pix->width;
-		mf->height	= pix->height;
-		return;
-	}
-
-	/* 1.-2. Current camera scales and subwin - cached. */
-
-	dev_geo(dev, "2: subwin %ux%u@%u:%u\n",
-		subrect->width, subrect->height,
-		subrect->left, subrect->top);
-
-	/*
-	 * 3. Calculate new combined scales from input sub-window to requested
-	 *    user window.
-	 */
-
-	/*
-	 * TODO: CEU cannot scale images larger than VGA to smaller than SubQCIF
-	 * (128x96) or larger than VGA
-	 */
-	scale_h = soc_camera_calc_scale(subrect->width, shift, pix->width);
-	scale_v = soc_camera_calc_scale(subrect->height, shift, pix->height);
-
-	dev_geo(dev, "3: scales %u:%u\n", scale_h, scale_v);
-
-	/*
-	 * 4. Calculate desired client output window by applying combined scales
-	 *    to client (real) input window.
-	 */
-	mf->width = soc_camera_shift_scale(rect->width, shift, scale_h);
-	mf->height = soc_camera_shift_scale(rect->height, shift, scale_v);
 }
 
 /* Similar to set_crop multistage iterative algorithm */

drivers/media/platform/soc_camera/soc_scale_crop.c

···
+/*
+ * soc-camera generic scaling-cropping manipulation functions
+ *
+ * Copyright (C) 2013 Guennadi Liakhovetski <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include <linux/device.h>
+#include <linux/module.h>
+
+#include <media/soc_camera.h>
+#include <media/v4l2-common.h>
+
+#include "soc_scale_crop.h"
+
+#ifdef DEBUG_GEOMETRY
+#define dev_geo	dev_info
+#else
+#define dev_geo	dev_dbg
+#endif
+
+/* Check if any dimension of r1 is smaller than respective one of r2 */
+static bool is_smaller(const struct v4l2_rect *r1, const struct v4l2_rect *r2)
+{
+	return r1->width < r2->width || r1->height < r2->height;
+}
+
+/* Check if r1 fails to cover r2 */
+static bool is_inside(const struct v4l2_rect *r1, const struct v4l2_rect *r2)
+{
+	return r1->left > r2->left || r1->top > r2->top ||
+		r1->left + r1->width < r2->left + r2->width ||
+		r1->top + r1->height < r2->top + r2->height;
+}
+
+/* Get and store current client crop */
+int soc_camera_client_g_rect(struct v4l2_subdev *sd, struct v4l2_rect *rect)
+{
+	struct v4l2_crop crop;
+	struct v4l2_cropcap cap;
+	int ret;
+
+	crop.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+
+	ret = v4l2_subdev_call(sd, video, g_crop, &crop);
+	if (!ret) {
+		*rect = crop.c;
+		return ret;
+	}
+
+	/* Camera driver doesn't support .g_crop(), assume default rectangle */
+	cap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+
+	ret = v4l2_subdev_call(sd, video, cropcap, &cap);
+	if (!ret)
+		*rect = cap.defrect;
+
+	return ret;
+}
+EXPORT_SYMBOL(soc_camera_client_g_rect);
+
+/* Client crop has changed, update our sub-rectangle to remain within the area */
+static void update_subrect(struct v4l2_rect *rect, struct v4l2_rect *subrect)
+{
+	if (rect->width < subrect->width)
+		subrect->width = rect->width;
+
+	if (rect->height < subrect->height)
+		subrect->height = rect->height;
+
+	if (rect->left > subrect->left)
+		subrect->left = rect->left;
+	else if (rect->left + rect->width >
+		 subrect->left + subrect->width)
+		subrect->left = rect->left + rect->width -
+			subrect->width;
+
+	if (rect->top > subrect->top)
+		subrect->top = rect->top;
+	else if (rect->top + rect->height >
+		 subrect->top + subrect->height)
+		subrect->top = rect->top + rect->height -
+			subrect->height;
+}
+
+/*
+ * The common for both scaling and cropping iterative approach is:
+ * 1. try if the client can produce exactly what requested by the user
+ * 2. if (1) failed, try to double the client image until we get one big enough
+ * 3. if (2) failed, try to request the maximum image
+ */
+int soc_camera_client_s_crop(struct v4l2_subdev *sd,
+			struct v4l2_crop *crop, struct v4l2_crop *cam_crop,
+			struct v4l2_rect *target_rect, struct v4l2_rect *subrect)
+{
+	struct v4l2_rect *rect = &crop->c, *cam_rect = &cam_crop->c;
+	struct device *dev = sd->v4l2_dev->dev;
+	struct v4l2_cropcap cap;
+	int ret;
+	unsigned int width, height;
+
+	v4l2_subdev_call(sd, video, s_crop, crop);
+	ret = soc_camera_client_g_rect(sd, cam_rect);
+	if (ret < 0)
+		return ret;
+
+	/*
+	 * Now cam_crop contains the current camera input rectangle, and it must
+	 * be within camera cropcap bounds
+	 */
+	if (!memcmp(rect, cam_rect, sizeof(*rect))) {
+		/* Even if camera S_CROP failed, but camera rectangle matches */
+		dev_dbg(dev, "Camera S_CROP successful for %dx%d@%d:%d\n",
+			rect->width, rect->height, rect->left, rect->top);
+		*target_rect = *cam_rect;
+		return 0;
+	}
+
+	/* Try to fix cropping, that camera hasn't managed to set */
+	dev_geo(dev, "Fix camera S_CROP for %dx%d@%d:%d to %dx%d@%d:%d\n",
+		cam_rect->width, cam_rect->height,
+		cam_rect->left, cam_rect->top,
+		rect->width, rect->height, rect->left, rect->top);
+
+	/* We need sensor maximum rectangle */
+	ret = v4l2_subdev_call(sd, video, cropcap, &cap);
+	if (ret < 0)
+		return ret;
+
+	/* Put user requested rectangle within sensor bounds */
+	soc_camera_limit_side(&rect->left, &rect->width, cap.bounds.left, 2,
+			      cap.bounds.width);
+	soc_camera_limit_side(&rect->top, &rect->height, cap.bounds.top, 4,
+			      cap.bounds.height);
+
+	/*
+	 * Popular special case - some cameras can only handle fixed sizes like
+	 * QVGA, VGA,... Take care to avoid infinite loop.
+	 */
+	width = max(cam_rect->width, 2);
+	height = max(cam_rect->height, 2);
+
+	/*
+	 * Loop as long as sensor is not covering the requested rectangle and
+	 * is still within its bounds
+	 */
+	while (!ret && (is_smaller(cam_rect, rect) ||
+			is_inside(cam_rect, rect)) &&
+	       (cap.bounds.width > width || cap.bounds.height > height)) {
+
+		width *= 2;
+		height *= 2;
+
+		cam_rect->width = width;
+		cam_rect->height = height;
+
+		/*
+		 * We do not know what capabilities the camera has to set up
+		 * left and top borders. We could try to be smarter in iterating
+		 * them, e.g., if camera current left is to the right of the
+		 * target left, set it to the middle point between the current
+		 * left and minimum left. But that would add too much
+		 * complexity: we would have to iterate each border separately.
+		 * Instead we just drop to the left and top bounds.
+		 */
+		if (cam_rect->left > rect->left)
+			cam_rect->left = cap.bounds.left;
+
+		if (cam_rect->left + cam_rect->width < rect->left + rect->width)
+			cam_rect->width = rect->left + rect->width -
+				cam_rect->left;
+
+		if (cam_rect->top > rect->top)
+			cam_rect->top = cap.bounds.top;
+
+		if (cam_rect->top + cam_rect->height < rect->top + rect->height)
+			cam_rect->height = rect->top + rect->height -
+				cam_rect->top;
+
+		v4l2_subdev_call(sd, video, s_crop, cam_crop);
+		ret = soc_camera_client_g_rect(sd, cam_rect);
+		dev_geo(dev, "Camera S_CROP %d for %dx%d@%d:%d\n", ret,
+			cam_rect->width, cam_rect->height,
+			cam_rect->left, cam_rect->top);
+	}
+
+	/* S_CROP must not modify the rectangle */
+	if (is_smaller(cam_rect, rect) || is_inside(cam_rect, rect)) {
+		/*
+		 * The camera failed to configure a suitable cropping,
+		 * we cannot use the current rectangle, set to max
+		 */
+		*cam_rect = cap.bounds;
+		v4l2_subdev_call(sd, video, s_crop, cam_crop);
+		ret = soc_camera_client_g_rect(sd, cam_rect);
+		dev_geo(dev, "Camera S_CROP %d for max %dx%d@%d:%d\n", ret,
+			cam_rect->width, cam_rect->height,
+			cam_rect->left, cam_rect->top);
+	}
+
+	if (!ret) {
+		*target_rect = *cam_rect;
+		update_subrect(target_rect, subrect);
+	}
+
+	return ret;
+}
+EXPORT_SYMBOL(soc_camera_client_s_crop);
+
+/* Iterative s_mbus_fmt, also updates cached client crop on success */
+static int client_s_fmt(struct soc_camera_device *icd,
+			struct v4l2_rect *rect, struct v4l2_rect *subrect,
+			unsigned int max_width, unsigned int max_height,
+			struct v4l2_mbus_framefmt *mf, bool host_can_scale)
+{
+	struct v4l2_subdev *sd = soc_camera_to_subdev(icd);
+	struct device *dev = icd->parent;
+	unsigned int width = mf->width, height = mf->height, tmp_w, tmp_h;
+	struct v4l2_cropcap cap;
+	bool ceu_1to1;
+	int ret;
+
+	ret = v4l2_device_call_until_err(sd->v4l2_dev,
+					 soc_camera_grp_id(icd), video,
+					 s_mbus_fmt, mf);
+	if (ret < 0)
+		return ret;
+
+	dev_geo(dev, "camera scaled to %ux%u\n", mf->width, mf->height);
+
+	if (width == mf->width && height == mf->height) {
+		/* Perfect! The client has done it all. */
+		ceu_1to1 = true;
+		goto update_cache;
+	}
+
+	ceu_1to1 = false;
+	if (!host_can_scale)
+		goto update_cache;
+
+	cap.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
+
+	ret = v4l2_subdev_call(sd, video, cropcap, &cap);
+	if (ret < 0)
+		return ret;
+
+	if (max_width > cap.bounds.width)
+		max_width = cap.bounds.width;
+	if (max_height > cap.bounds.height)
+		max_height = cap.bounds.height;
+
+	/* Camera set a format, but geometry is not precise, try to improve */
+	tmp_w = mf->width;
+	tmp_h = mf->height;
+
+	/* width <= max_width && height <= max_height - guaranteed by try_fmt */
+	while ((width > tmp_w || height > tmp_h) &&
+	       tmp_w < max_width && tmp_h < max_height) {
+		tmp_w = min(2 * tmp_w, max_width);
+		tmp_h = min(2 * tmp_h, max_height);
+		mf->width = tmp_w;
+		mf->height = tmp_h;
+		ret = v4l2_device_call_until_err(sd->v4l2_dev,
+					soc_camera_grp_id(icd), video,
+					s_mbus_fmt, mf);
+		dev_geo(dev, "Camera scaled to %ux%u\n",
+			mf->width, mf->height);
+		if (ret < 0) {
+			/* This shouldn't happen */
+			dev_err(dev, "Client failed to set format: %d\n", ret);
+			return ret;
+		}
+	}
+
+update_cache:
+	/* Update cache */
+	ret = soc_camera_client_g_rect(sd, rect);
+	if (ret < 0)
+		return ret;
+
+	if (ceu_1to1)
+		*subrect = *rect;
+	else
+		update_subrect(rect, subrect);
+
+	return 0;
+}
+
+/**
+ * @icd		- soc-camera device
+ * @rect	- camera cropping window
+ * @subrect	- part of rect, sent to the user
+ * @mf		- in- / output camera output window
+ * @width	- on input: max host input width
+ *		  on output: user width, mapped back to input
+ * @height	- on input: max host input height
+ *		  on output: user height, mapped back to input
+ * @host_can_scale - host can scale this pixel format
+ * @shift	- shift, used for scaling
+ */
+int soc_camera_client_scale(struct soc_camera_device *icd,
+			struct v4l2_rect *rect, struct v4l2_rect *subrect,
+			struct v4l2_mbus_framefmt *mf,
+			unsigned int *width, unsigned int *height,
+			bool host_can_scale, unsigned int shift)
+{
+	struct device *dev = icd->parent;
+	struct v4l2_mbus_framefmt mf_tmp = *mf;
+	unsigned int scale_h, scale_v;
+	int ret;
+
+	/*
+	 * 5. Apply iterative camera S_FMT for camera user window (also updates
+	 *    client crop cache and the imaginary sub-rectangle).
+	 */
+	ret = client_s_fmt(icd, rect, subrect, *width, *height,
+			   &mf_tmp, host_can_scale);
+	if (ret < 0)
+		return ret;
+
+	dev_geo(dev, "5: camera scaled to %ux%u\n",
+		mf_tmp.width, mf_tmp.height);
+
+	/* 6. Retrieve camera output window (g_fmt) */
+
+	/* unneeded - it is already in "mf_tmp" */
+
+	/* 7. Calculate new client scales. */
+	scale_h = soc_camera_calc_scale(rect->width, shift, mf_tmp.width);
+	scale_v = soc_camera_calc_scale(rect->height, shift, mf_tmp.height);
+
+	mf->width	= mf_tmp.width;
+	mf->height	= mf_tmp.height;
+	mf->colorspace	= mf_tmp.colorspace;
+
+	/*
+	 * 8. Calculate new CEU crop - apply camera scales to previously
+	 *    updated "effective" crop.
+	 */
+	*width = soc_camera_shift_scale(subrect->width, shift, scale_h);
+	*height = soc_camera_shift_scale(subrect->height, shift, scale_v);
+
+	dev_geo(dev, "8: new client sub-window %ux%u\n", *width, *height);
+
+	return 0;
+}
+EXPORT_SYMBOL(soc_camera_client_scale);
+
+/*
+ * Calculate real client output window by applying new scales to the current
+ * client crop. New scales are calculated from the requested output format and
+ * CEU crop, mapped backed onto the client input (subrect).
+ */
+void soc_camera_calc_client_output(struct soc_camera_device *icd,
+		struct v4l2_rect *rect, struct v4l2_rect *subrect,
+		const struct v4l2_pix_format *pix, struct v4l2_mbus_framefmt *mf,
+		unsigned int shift)
+{
+	struct device *dev = icd->parent;
+	unsigned int scale_v, scale_h;
+
+	if (subrect->width == rect->width &&
+	    subrect->height == rect->height) {
+		/* No sub-cropping */
+		mf->width	= pix->width;
+		mf->height	= pix->height;
+		return;
+	}
+
+	/* 1.-2. Current camera scales and subwin - cached. */
+
+	dev_geo(dev, "2: subwin %ux%u@%u:%u\n",
+		subrect->width, subrect->height,
+		subrect->left, subrect->top);
+
+	/*
+	 * 3. Calculate new combined scales from input sub-window to requested
+	 *    user window.
+	 */
+
+	/*
+	 * TODO: CEU cannot scale images larger than VGA to smaller than SubQCIF
+	 * (128x96) or larger than VGA
+	 */
+	scale_h = soc_camera_calc_scale(subrect->width, shift, pix->width);
+	scale_v = soc_camera_calc_scale(subrect->height, shift, pix->height);
+
+	dev_geo(dev, "3: scales %u:%u\n", scale_h, scale_v);
+
+	/*
+	 * 4. Calculate desired client output window by applying combined scales
+	 *    to client (real) input window.
+	 */
+	mf->width = soc_camera_shift_scale(rect->width, shift, scale_h);
+	mf->height = soc_camera_shift_scale(rect->height, shift, scale_v);
+}
+EXPORT_SYMBOL(soc_camera_calc_client_output);

drivers/media/platform/soc_camera/soc_scale_crop.h

···
+/*
+ * soc-camera generic scaling-cropping manipulation functions
+ *
+ * Copyright (C) 2013 Guennadi Liakhovetski <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#ifndef SOC_SCALE_CROP_H
+#define SOC_SCALE_CROP_H
+
+#include <linux/kernel.h>
+
+struct soc_camera_device;
+
+struct v4l2_crop;
+struct v4l2_mbus_framefmt;
+struct v4l2_pix_format;
+struct v4l2_rect;
+struct v4l2_subdev;
+
+static inline unsigned int soc_camera_shift_scale(unsigned int size,
+				unsigned int shift, unsigned int scale)
+{
+	return DIV_ROUND_CLOSEST(size << shift, scale);
+}
+
+#define soc_camera_calc_scale(in, shift, out) soc_camera_shift_scale(in, shift, out)
+
+int soc_camera_client_g_rect(struct v4l2_subdev *sd, struct v4l2_rect *rect);
+int soc_camera_client_s_crop(struct v4l2_subdev *sd,
+			struct v4l2_crop *crop, struct v4l2_crop *cam_crop,
+			struct v4l2_rect *target_rect, struct v4l2_rect *subrect);
+int soc_camera_client_scale(struct soc_camera_device *icd,
+			struct v4l2_rect *rect, struct v4l2_rect *subrect,
+			struct v4l2_mbus_framefmt *mf,
+			unsigned int *width, unsigned int *height,
+			bool host_can_scale, unsigned int shift);
+void soc_camera_calc_client_output(struct soc_camera_device *icd,
+		struct v4l2_rect *rect, struct v4l2_rect *subrect,
+		const struct v4l2_pix_format *pix, struct v4l2_mbus_framefmt *mf,
+		unsigned int shift);
+
+#endif