video: bcm2708_fb: Disable FB if no displays found

If the firmware hasn't detected a display, the driver would assume
one display was available, but because it had failed to retrieve the
display size it would try to allocate a zero-sized buffer.

Avoid the allocation failure by bailing out early if no display is
found.

See: https://github.com/raspberrypi/linux/issues/3598

Signed-off-by: Phil Elwell <phil@raspberrypi.com>

diff --git a/drivers/video/fbdev/bcm2708_fb.c b/drivers/video/fbdev/bcm2708_fb.c
index 17e9260..dac5c02 100644 (file)
--- a/drivers/video/fbdev/bcm2708_fb.c
+++ b/drivers/video/fbdev/bcm2708_fb.c
@@ -1092,10 +1092,9 @@ static int bcm2708_fb_probe(struct platform_device *dev)
         * set one display
         */
        if (ret || num_displays == 0) {
-               num_displays = 1;
                dev_err(&dev->dev,
-                       "Unable to determine number of FB's. Assuming 1\n");
-               ret = 0;
+                       "Unable to determine number of FBs. Disabling driver.\n");
+               return -ENOENT;
        } else {
                fbdev->firmware_supports_multifb = 1;
        }