[PATCH 2/4] drm: Refuse to create zero width/height cmdline modes

[Ville Syrjala <ville.syrjala@linux.intel.com>]

From: Ville Syrjälä <ville.syrjala@linux.intel.com>

If the user specifies zero width/height cmdline mode i915 will
blow up as the fbdev path will bypass the regular fb sanity
check that would otherwise have refused to create a framebuffer
with zero width/height.

The reason I thought to try this is so that I can force a specific
depth for fbdev without actually having to hardcode the mode
on the kernel cmdline. Eg. if I pass video=0x0-8 I will get an
8bpp framebuffer at my monitor's native resolution.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
---
 drivers/gpu/drm/drm_modes.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
index 5a07a28fec6d..b36248a5d826 100644
--- a/drivers/gpu/drm/drm_modes.c
+++ b/drivers/gpu/drm/drm_modes.c
@@ -1593,6 +1593,9 @@ drm_mode_create_from_cmdline_mode(struct drm_device *dev,
 {
 	struct drm_display_mode *mode;
 
+	if (cmd->xres == 0 || cmd->yres == 0)
+		return NULL;
+
 	if (cmd->cvt)
 		mode = drm_cvt_mode(dev,
 				    cmd->xres, cmd->yres,
-- 
2.21.0

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