[PATCH 1/3] drm/fb: fix FBIOGET/PUT_VSCREENINFO pixel clock handling

Clemens Ladisch
2009-11-02T07:41:11Z

When the framebuffer driver does not publish detailed timing information
for the current video mode, the correct value for the pixclock field is
zero, not -1.

Since pixclock is actually unsigned, the value -1 would be interpreted
as 4294967295 picoseconds (i.e., about 4 milliseconds) by
register_framebuffer() and userspace programs.

This patch allows X.org's fbdev driver to work.

Signed-off-by: Clemens Ladisch <clemens@ladisch.de>

--- linux-2.6/drivers/gpu/drm/drm_fb_helper.c
+++ linux-2.6/drivers/gpu/drm/drm_fb_helper.c
@@ -583,7 +583,7 @@ int drm_fb_helper_check_var(struct fb_va
struct drm_framebuffer *fb = fb_helper->fb;
int depth;

- if (var->pixclock == -1 || !var->pixclock)
+ if (var->pixclock != 0)
return -EINVAL;

/* Need to resize the fb object !!! */
@@ -675,7 +675,7 @@ int drm_fb_helper_set_par(struct fb_info
int ret;
int i;

- if (var->pixclock != -1) {
+ if (var->pixclock != 0) {
DRM_ERROR("PIXEL CLCOK SET\n");
return -EINVAL;
}
@@ -888,7 +888,7 @@ int drm_fb_helper_single_fb_probe(struct
fb_helper->fb = fb;

if (new_fb) {
- info->var.pixclock = -1;
+ info->var.pixclock = 0;
if (register_framebuffer(info) < 0)
return -EINVAL;
} else {