Re: bug: kernel bug when unbinding EFI framebuffer

On Wed, 13 May 2020 at 06:03, Dave Airlie [off-list ref] wrote:

On Sat, 2 May 2020 at 22:36, Fabian Mastenbroek [off-list ref] wrote:

quoted

Hi,

When I try to unbind the EFI framebuffer via:

        echo -n efi-framebuffer.0 > /sys/bus/platform/drivers/efi-framebuffer/unbind

Can I ask why?

nouveau kicks the efifb off the hw, and unregisters it, but when you
unbind it it tries to unregister again.

It might be possible to block this, but not sure of the point, efifb
is a built-in, you can't unload the module to save memory.

diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
index 65491ae74808..87405545a903 100644
--- a/drivers/video/fbdev/efifb.c
+++ b/drivers/video/fbdev/efifb.c

@@ -598,7 +598,8 @@ static int efifb_remove(struct platform_device *pdev)
 {
        struct fb_info *info = platform_get_drvdata(pdev);

-       unregister_framebuffer(info);
+       if (info->dev)
+               unregister_framebuffer(info);
        sysfs_remove_groups(&pdev->dev.kobj, efifb_groups);
        framebuffer_release(info);

something like that (applied by hand, this is just pasted out into
gmail so won't apply), might stop the oops.

Dave.

Dave.