From 96fe6a2109db29cd15b90a093c16e6cb4b19371a Mon Sep 17 00:00:00 2001 From: "Antonino A. Daplas" Date: Fri, 9 Sep 2005 13:09:58 -0700 Subject: [PATCH] fbdev: Add VESA Coordinated Video Timings (CVT) support The Coordinated Video Timings (CVT) is the latest standard approved by VESA concerning video timings generation. It addresses the limitation of GTF which is designed mainly for CRT displays. CRT's have a high blanking requirement (as much as 25% of the horizontal frame length) which artificially increases the pixelclock. Digital displays, on the other hand, needs to conserve the pixelclock as much as possible. The GTF also does not take into account the different aspect ratios in its calculation. The new function added is fb_find_mode_cvt(). It is called by fb_find_mode() if it recognizes a mode option string formatted for CVT. The format is: x[M][R][-][][i][m] The 'M' tells the function to calculate using CVT. On it's own, it will compute a timing for CRT displays at 60Hz. If the 'R' is specified, 'reduced blanking' computation will be used, best for flatpanels. The 'i' and the 'm' is for 'interlaced mode' and 'with margins' respectively. To determine if CVT was used, check for dmesg for something like this: CVT Mode - M[-R], ie: .480M3-R (800x600 reduced blanking) where: pix - product of xres and yres, in MB M - is a CVT mode n - the aspect ratio (3 - 4:3; 4 - 5:4; 9 - 16:9, 15:9; A - 16:10) -R - reduced blanking Signed-off-by: Antonino Daplas Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/fb.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux') diff --git a/include/linux/fb.h b/include/linux/fb.h index 34814a0b237..9a4f035e9fd 100644 --- a/include/linux/fb.h +++ b/include/linux/fb.h @@ -866,6 +866,7 @@ extern const unsigned char *fb_firmware_edid(struct device *device); extern void fb_edid_to_monspecs(unsigned char *edid, struct fb_monspecs *specs); extern void fb_destroy_modedb(struct fb_videomode *modedb); +extern int fb_find_mode_cvt(struct fb_videomode *mode, int margins, int rb); /* drivers/video/modedb.c */ #define VESA_MODEDB_SIZE 34 -- cgit v1.2.3