Re: [PATCH] fb: fix lost console when the user unplugs a USB adapter

AFAIU calling unregister_framebuffer() with open fd's is just fine as
long as fb_info with buffers stay intact. All it does is to remove the
fbX from userspace. Cleanup can be done in fb_ops->fb_destroy.

I have been working on generic fbdev emulation for DRM [1] and I did a
test now to see what would happen if I did unbind the driver from the
device. It worked as expected if I didn't have another fbdev present,
but if there is an fb0 and I remove fb1 with a console on it, I would
sometimes get crashes, often with a call to cursor_timer_handler() in
the traceback.

I think there's index mixup in fbcon_fb_unbind(), at least this change
seems to solve the immediate problem:

diff --git a/drivers/video/fbdev/core/fbcon.c

b/drivers/video/fbdev/core/fbcon.c
index 5fb156bdcf4e..271b9b988b73 100644

--- a/drivers/video/fbdev/core/fbcon.c
+++ b/drivers/video/fbdev/core/fbcon.c

@@ -3066,7 +3072,7 @@ static int fbcon_fb_unbind(int idx)

        for (i = first_fb_vc; i <= last_fb_vc; i++) {
                if (con2fb_map[i] != idx &&
                    con2fb_map[i] != -1) {
-                       new_idx = i;
+                       new_idx = con2fb_map[i];
                        break;
                }
        }