fbdev: Add FOURCC-based format configuration API

This API will be used to support YUV frame buffer formats in a standard
way.

Last but not least, create a much needed fbdev API documentation and
document the format setting APIs.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/video/fbmem.c b/drivers/video/fbmem.c
index ad936295d8f4..ac9141b85356 100644
--- a/drivers/video/fbmem.c
+++ b/drivers/video/fbmem.c
@@ -967,6 +967,20 @@ fb_set_var(struct fb_info *info, struct fb_var_screeninfo *var)
             memcmp(&info->var, var, sizeof(struct fb_var_screeninfo))) {
                 u32 activate = var->activate;
 
+                /* When using FOURCC mode, make sure the red, green, blue and
+                 * transp fields are set to 0.
+                 */
+                if ((info->fix.capabilities & FB_CAP_FOURCC) &&
+                    var->grayscale > 1) {
+                        if (var->red.offset     || var->green.offset    ||
+                            var->blue.offset    || var->transp.offset   ||
+                            var->red.length     || var->green.length    ||
+                            var->blue.length    || var->transp.length   ||
+                            var->red.msb_right  || var->green.msb_right ||
+                            var->blue.msb_right || var->transp.msb_right)
+                                return -EINVAL;
+                }
+
                 if (!info->fbops->fb_check_var) {
                         *var = info->var;
                         goto done;