[RFC PATCH v2 1/3] drm/fourcc: Add 'bpp' field for formats with non-integer bytes-per-pixel

[Brian Starkey <brian.starkey@arm.com>]

Some formats have a non-integer number of bytes per pixel, which can't
be handled with the existing 'cpp' field in drm_format_info. To handle
these formats, add a 'bpp' field, which is only used if cpp[0] == 0.

This updates all the users of format->cpp in the core DRM code,
converting them to use a new function to get the bits-per-pixel for any
format.

It's assumed that drivers will use the 'bpp' field when they add support
for pixel formats with non-integer bytes-per-pixel.

Signed-off-by: Brian Starkey <brian.starkey@arm.com>
---
 drivers/gpu/drm/drm_fb_cma_helper.c          |  6 +++-
 drivers/gpu/drm/drm_fb_helper.c              |  8 +++--
 drivers/gpu/drm/drm_fourcc.c                 | 50 ++++++++++++++++++++++++++++
 drivers/gpu/drm/drm_framebuffer.c            |  8 ++---
 drivers/gpu/drm/drm_gem_framebuffer_helper.c |  3 +-
 include/drm/drm_fourcc.h                     |  4 +++
 6 files changed, 70 insertions(+), 9 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
index 186d00adfb5f..e279d70d3e60 100644
--- a/drivers/gpu/drm/drm_fb_cma_helper.c
+++ b/drivers/gpu/drm/drm_fb_cma_helper.c
@@ -118,13 +118,17 @@ dma_addr_t drm_fb_cma_get_gem_addr(struct drm_framebuffer *fb,
 {
 	struct drm_gem_cma_object *obj;
 	dma_addr_t paddr;
+	u8 bpp = drm_format_info_plane_bpp(fb->format, plane);
+
+	/* This can't work for non-integer bytes-per-pixel */
+	WARN_ON(bpp % 8);
 
 	obj = drm_fb_cma_get_gem_obj(fb, plane);
 	if (!obj)
 		return 0;
 
 	paddr = obj->paddr + fb->offsets[plane];
-	paddr += fb->format->cpp[plane] * (state->src_x >> 16);
+	paddr += (bpp / 8) * (state->src_x >> 16);
 	paddr += fb->pitches[plane] * (state->src_y >> 16);
 
 	return paddr;
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 0646b108030b..ab369f250af4 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1572,6 +1572,7 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
 	struct drm_fb_helper *fb_helper = info->par;
 	struct drm_framebuffer *fb = fb_helper->fb;
 	int depth;
+	u8 bpp = drm_format_info_plane_bpp(fb->format, 0);
 
 	if (var->pixclock != 0 || in_dbg_master())
 		return -EINVAL;
@@ -1580,14 +1581,14 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
 	 * Changes struct fb_var_screeninfo are currently not pushed back
 	 * to KMS, hence fail if different settings are requested.
 	 */
-	if (var->bits_per_pixel != fb->format->cpp[0] * 8 ||
+	if (var->bits_per_pixel != bpp ||
 	    var->xres > fb->width || var->yres > fb->height ||
 	    var->xres_virtual > fb->width || var->yres_virtual > fb->height) {
 		DRM_DEBUG("fb requested width/height/bpp can't fit in current fb "
 			  "request %dx%d-%d (virtual %dx%d) > %dx%d-%d\n",
 			  var->xres, var->yres, var->bits_per_pixel,
 			  var->xres_virtual, var->yres_virtual,
-			  fb->width, fb->height, fb->format->cpp[0] * 8);
+			  fb->width, fb->height, bpp);
 		return -EINVAL;
 	}
 
@@ -1949,11 +1950,12 @@ void drm_fb_helper_fill_var(struct fb_info *info, struct drm_fb_helper *fb_helpe
 			    uint32_t fb_width, uint32_t fb_height)
 {
 	struct drm_framebuffer *fb = fb_helper->fb;
+	u8 bpp = drm_format_info_plane_bpp(fb->format, 0);
 
 	info->pseudo_palette = fb_helper->pseudo_palette;
 	info->var.xres_virtual = fb->width;
 	info->var.yres_virtual = fb->height;
-	info->var.bits_per_pixel = fb->format->cpp[0] * 8;
+	info->var.bits_per_pixel = bpp;
 	info->var.accel_flags = FB_ACCELF_TEXT;
 	info->var.xoffset = 0;
 	info->var.yoffset = 0;
diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
index 3b42c25bd58d..bb28919c32f3 100644
--- a/drivers/gpu/drm/drm_fourcc.c
+++ b/drivers/gpu/drm/drm_fourcc.c
@@ -272,10 +272,60 @@ int drm_format_plane_cpp(uint32_t format, int plane)
 	if (!info || plane >= info->num_planes)
 		return 0;
 
+	/*
+	 * Not valid for formats with non-integer cpp,
+	 * use drm_format{_info}_plane_bpp instead
+	 */
+	WARN_ON(!info->cpp[0]);
+
 	return info->cpp[plane];
 }
 EXPORT_SYMBOL(drm_format_plane_cpp);
 
+/**
+ * drm_format_plane_bpp - determine the bits per pixel value
+ * @format: pixel format (DRM_FORMAT_*)
+ * @plane: plane index
+ *
+ * Returns:
+ * The bits per pixel value for the specified plane.
+ */
+int drm_format_plane_bpp(uint32_t format, int plane)
+{
+	const struct drm_format_info *info;
+
+	info = drm_format_info(format);
+	if (!info)
+		return 0;
+
+	return drm_format_info_plane_bpp(info, plane);
+}
+EXPORT_SYMBOL(drm_format_plane_bpp);
+
+/**
+ * drm_format_info_plane_bpp - determine the bits per pixel value
+ *
+ * Convenience function which handles formats with both integer
+ * and non-integer bytes-per-pixel.
+ *
+ * @format: pixel format info structure
+ * @plane: plane index
+ *
+ * Returns:
+ * The bits per pixel value for the specified plane.
+ */
+int drm_format_info_plane_bpp(const struct drm_format_info *info, int plane)
+{
+	if (plane >= info->num_planes)
+		return 0;
+
+	if (info->cpp[0])
+		return info->cpp[plane] * 8;
+
+	return info->bpp[plane];
+}
+EXPORT_SYMBOL(drm_format_info_plane_bpp);
+
 /**
  * drm_format_horz_chroma_subsampling - get the horizontal chroma subsampling factor
  * @format: pixel format (DRM_FORMAT_*)
diff --git a/drivers/gpu/drm/drm_framebuffer.c b/drivers/gpu/drm/drm_framebuffer.c
index 8c4d32adcc17..7e00360ff70d 100644
--- a/drivers/gpu/drm/drm_framebuffer.c
+++ b/drivers/gpu/drm/drm_framebuffer.c
@@ -185,20 +185,20 @@ static int framebuffer_check(struct drm_device *dev,
 	for (i = 0; i < info->num_planes; i++) {
 		unsigned int width = fb_plane_width(r->width, info, i);
 		unsigned int height = fb_plane_height(r->height, info, i);
-		unsigned int cpp = info->cpp[i];
+		unsigned int bpp = drm_format_info_plane_bpp(info, i);
 
 		if (!r->handles[i]) {
 			DRM_DEBUG_KMS("no buffer object handle for plane %d\n", i);
 			return -EINVAL;
 		}
 
-		if ((uint64_t) width * cpp > UINT_MAX)
+		if ((uint64_t) DIV_ROUND_UP(width * bpp, 8) > UINT_MAX)
 			return -ERANGE;
 
 		if ((uint64_t) height * r->pitches[i] + r->offsets[i] > UINT_MAX)
 			return -ERANGE;
 
-		if (r->pitches[i] < width * cpp) {
+		if ((uint64_t) r->pitches[i] * 8 < (uint64_t) width * bpp) {
 			DRM_DEBUG_KMS("bad pitch %u for plane %d\n", r->pitches[i], i);
 			return -EINVAL;
 		}
@@ -476,7 +476,7 @@ int drm_mode_getfb(struct drm_device *dev,
 	r->height = fb->height;
 	r->width = fb->width;
 	r->depth = fb->format->depth;
-	r->bpp = fb->format->cpp[0] * 8;
+	r->bpp = drm_format_info_plane_bpp(fb->format, 0);
 	r->pitch = fb->pitches[0];
 
 	/* GET_FB() is an unprivileged ioctl so we must not return a
diff --git a/drivers/gpu/drm/drm_gem_framebuffer_helper.c b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
index acfbc0641a06..dfe224ccaeba 100644
--- a/drivers/gpu/drm/drm_gem_framebuffer_helper.c
+++ b/drivers/gpu/drm/drm_gem_framebuffer_helper.c
@@ -161,6 +161,7 @@ drm_gem_fb_create_with_funcs(struct drm_device *dev, struct drm_file *file,
 		unsigned int width = mode_cmd->width / (i ? info->hsub : 1);
 		unsigned int height = mode_cmd->height / (i ? info->vsub : 1);
 		unsigned int min_size;
+		u8 bpp = drm_format_info_plane_bpp(fb->format, i);
 
 		objs[i] = drm_gem_object_lookup(file, mode_cmd->handles[i]);
 		if (!objs[i]) {
@@ -170,7 +171,7 @@ drm_gem_fb_create_with_funcs(struct drm_device *dev, struct drm_file *file,
 		}
 
 		min_size = (height - 1) * mode_cmd->pitches[i]
-			 + width * info->cpp[i]
+			 + DIV_ROUND_UP(width * bpp, 8)
 			 + mode_cmd->offsets[i];
 
 		if (objs[i]->size < min_size) {
diff --git a/include/drm/drm_fourcc.h b/include/drm/drm_fourcc.h
index 3e86408dac9f..d4af4dab1623 100644
--- a/include/drm/drm_fourcc.h
+++ b/include/drm/drm_fourcc.h
@@ -36,6 +36,7 @@ struct drm_mode_fb_cmd2;
  *	use in new code and set to 0 for new formats.
  * @num_planes: Number of color planes (1 to 3)
  * @cpp: Number of bytes per pixel (per plane)
+ * @bpp: Number of bits per pixel (per plane), only valid if cpp[0] == 0.
  * @hsub: Horizontal chroma subsampling factor
  * @vsub: Vertical chroma subsampling factor
  * @has_alpha: Does the format embeds an alpha component?
@@ -45,6 +46,7 @@ struct drm_format_info {
 	u8 depth;
 	u8 num_planes;
 	u8 cpp[3];
+	u8 bpp[3];
 	u8 hsub;
 	u8 vsub;
 	bool has_alpha;
@@ -66,6 +68,8 @@ drm_get_format_info(struct drm_device *dev,
 uint32_t drm_mode_legacy_fb_format(uint32_t bpp, uint32_t depth);
 int drm_format_num_planes(uint32_t format);
 int drm_format_plane_cpp(uint32_t format, int plane);
+int drm_format_plane_bpp(uint32_t format, int plane);
+int drm_format_info_plane_bpp(const struct drm_format_info *format, int plane);
 int drm_format_horz_chroma_subsampling(uint32_t format);
 int drm_format_vert_chroma_subsampling(uint32_t format);
 int drm_format_plane_width(int width, uint32_t format, int plane);
-- 
2.16.1