Re: udlfb: remove sysfs framebuffer device with USB .disconnect()

On Sat, Jan 21, 2012 at 14:44, Florian Tobias Schandinat
[off-list ref] wrote:

On 01/20/2012 08:18 PM, Kay Sievers wrote:

quoted

+++ b/drivers/video/fbmem.c

@@ -1672,7 +1672,7 @@ static int do_unregister_framebuffer(str

      registered_fb[i] = NULL;

Here registered_fb[fb_info->node] is set to NULL...

quoted

+int unlink_framebuffer(struct fb_info *fb_info)
+{
+     int i;
+
+     i = fb_info->node;
+     if (i < 0 || i >= FB_MAX || registered_fb[i] != fb_info)
+             return -EINVAL;

...and here you check whether it is still valid (did you copy the check from the
do_unregister_framebuffer?). So the code below would be never executed, when
called in this context.

That's true. If one calls the current _unregister() *before* calling
_unlink(), the _unlink() is a NOP. But that's intentional.

The _unlink() is only needed for stuff needs to be called when we are
required to 'orphan' the device before cleaning up. Normal,
non-hotpluggable devices do not need this, they can continue what they
do today.

The _unlink() call *can* be called before _unregister() if needed for
disconnecting it from the driver core parent and remove its userspace
visibility. If _unlink() is called before _unregister(), it passes the
check, the later _unregister() will also pass the check but get rid of
the entire device.

Kay