Re: [PATCH 2/9] fbdev: Put mmap for deferred I/O into drivers

On 3/3/22 21:58, Thomas Zimmermann wrote:

The fbdev mmap function fb_mmap() unconditionally overrides the driver's implementation if deferred I/O has been activated. This makes it hard to implement mmap with anything but a vmalloc()'ed software buffer. That is specifically a problem for DRM, where video memory is maintained by a memory manager.

Leave the mmap handling to drivers and expect them to call the helper for deferred I/O by thmeselves.

Signed-off-by: Thomas Zimmermann tzimmermann@suse.de

[snip]

• /*

• * FB deferred I/O want you to handle mmap in your drivers. At a
  

• * minimum, point struct fb_ops.fb_mmap to fb_deferred_io_mmap().
  

• */
  

• if (WARN_ON_ONCE(info->fbdefio))

• return -ENODEV;
  

Maybe part of that comment could be printed as a WARN_ON_ONCE() message ?

Regardless, the patch looks good to me:

Reviewed-by: Javier Martinez Canillas javierm@redhat.com