drm: Add mode_config .get_format_info() hook

Allow drivers to return a custom drm_format_info structure for special
fb layouts. We'll use this for the compression control surface in i915.

v2: Fix drm_get_format_info() kernel doc (Laurent)
    Don't pass 'dev' to the new hook (Laurent)
v3: s/compresssion/compression/ (Ben)

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Ben Widawsky <ben@bwidawsk.net>
Cc: Jason Ekstrand <jason@jlekstrand.net>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Ben Widawsky <ben@bwidawsk.net>
Link: http://patchwork.freedesktop.org/patch/msgid/20170321181218.10042-4-ville.syrjala@linux.intel.com

drivers/gpu/drm/drm_fb_cma_helper.c

@@ -177,7 +177,7 @@ struct drm_framebuffer *drm_fb_cma_create_with_funcs(struct drm_device *dev,
 	int ret;
 	int i;
 
-	info = drm_format_info(mode_cmd->pixel_format);
+	info = drm_get_format_info(dev, mode_cmd);
 	if (!info)
 		return ERR_PTR(-EINVAL);
 

drivers/gpu/drm/drm_fourcc.c

@@ -198,6 +198,31 @@ const struct drm_format_info *drm_format_info(u32 format)
 }
 EXPORT_SYMBOL(drm_format_info);
 
+/**
+ * drm_get_format_info - query information for a given framebuffer configuration
+ * @dev: DRM device
+ * @mode_cmd: metadata from the userspace fb creation request
+ *
+ * Returns:
+ * The instance of struct drm_format_info that describes the pixel format, or
+ * NULL if the format is unsupported.
+ */
+const struct drm_format_info *
+drm_get_format_info(struct drm_device *dev,
+		    const struct drm_mode_fb_cmd2 *mode_cmd)
+{
+	const struct drm_format_info *info = NULL;
+
+	if (dev->mode_config.funcs->get_format_info)
+		info = dev->mode_config.funcs->get_format_info(mode_cmd);
+
+	if (!info)
+		info = drm_format_info(mode_cmd->pixel_format);
+
+	return info;
+}
+EXPORT_SYMBOL(drm_get_format_info);
+
 /**
  * drm_format_num_planes - get the number of planes for format
  * @format: pixel format (DRM_FORMAT_*)

drivers/gpu/drm/drm_framebuffer.c

@@ -144,11 +144,13 @@ static int fb_plane_height(int height,
 	return DIV_ROUND_UP(height, format->vsub);
 }
 
-static int framebuffer_check(const struct drm_mode_fb_cmd2 *r)
+static int framebuffer_check(struct drm_device *dev,
+			     const struct drm_mode_fb_cmd2 *r)
 {
 	const struct drm_format_info *info;
 	int i;
 
+	/* check if the format is supported at all */
 	info = __drm_format_info(r->pixel_format & ~DRM_FORMAT_BIG_ENDIAN);
 	if (!info) {
 		struct drm_format_name_buf format_name;
@@ -158,6 +160,9 @@ static int framebuffer_check(const struct drm_mode_fb_cmd2 *r)
 		return -EINVAL;
 	}
 
+	/* now let the driver pick its own format info */
+	info = drm_get_format_info(dev, r);
+
 	if (r->width == 0) {
 		DRM_DEBUG_KMS("bad framebuffer width %u\n", r->width);
 		return -EINVAL;
@@ -281,7 +286,7 @@ drm_internal_framebuffer_create(struct drm_device *dev,
 		return ERR_PTR(-EINVAL);
 	}
 
-	ret = framebuffer_check(r);
+	ret = framebuffer_check(dev, r);
 	if (ret)
 		return ERR_PTR(ret);
 

drivers/gpu/drm/drm_modeset_helper.c

@@ -78,7 +78,7 @@ void drm_helper_mode_fill_fb_struct(struct drm_device *dev,
 	int i;
 
 	fb->dev = dev;
-	fb->format = drm_format_info(mode_cmd->pixel_format);
+	fb->format = drm_get_format_info(dev, mode_cmd);
 	fb->width = mode_cmd->width;
 	fb->height = mode_cmd->height;
 	for (i = 0; i < 4; i++) {

include/drm/drm_fourcc.h

@@ -25,6 +25,9 @@
 #include <linux/types.h>
 #include <uapi/drm/drm_fourcc.h>
 
+struct drm_device;
+struct drm_mode_fb_cmd2;
+
 /**
  * struct drm_format_info - information about a DRM format
  * @format: 4CC format identifier (DRM_FORMAT_*)
@@ -55,6 +58,9 @@ struct drm_format_name_buf {
 
 const struct drm_format_info *__drm_format_info(u32 format);
 const struct drm_format_info *drm_format_info(u32 format);
+const struct drm_format_info *
+drm_get_format_info(struct drm_device *dev,
+		    const struct drm_mode_fb_cmd2 *mode_cmd);
 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);

include/drm/drm_mode_config.h

@@ -34,6 +34,7 @@ struct drm_file;
 struct drm_device;
 struct drm_atomic_state;
 struct drm_mode_fb_cmd2;
+struct drm_format_info;
 
 /**
  * struct drm_mode_config_funcs - basic driver provided mode setting functions
@@ -69,6 +70,19 @@ struct drm_mode_config_funcs {
 					     struct drm_file *file_priv,
 					     const struct drm_mode_fb_cmd2 *mode_cmd);
 
+	/**
+	 * @get_format_info:
+	 *
+	 * Allows a driver to return custom format information for special
+	 * fb layouts (eg. ones with auxiliary compression control planes).
+	 *
+	 * RETURNS:
+	 *
+	 * The format information specific to the given fb metadata, or
+	 * NULL if none is found.
+	 */
+	const struct drm_format_info *(*get_format_info)(const struct drm_mode_fb_cmd2 *mode_cmd);
+
 	/**
 	 * @output_poll_changed:
 	 *