Nouveau - Sep 2024 - [PATCH v3 02/81] drm/fbdev-helper: Set and clear VGA switcheroo client from fb_info

Thomas Zimmermann <tzimmermann at suse.de> writes:

Hello Thomas,
> Call vga_switcheroo_client_fb_set() with the PCI device from the
> instance of struct fb_info. All fbdev clients now run these calls.
> For non-PCI devices or drivers without vga-switcheroo, this does
> nothing. For i915 and radeon, it allows these drivers to use a
> common fbdev client.
>
> The device is the same as the one stored in struct drm_client and
> struct drm_fb_helper, so there is no difference in behavior. Some
> NULL-pointer checks are being removed, where those pointers cannot
> be NULL.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
> ---
>  drivers/gpu/drm/drm_fb_helper.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c
b/drivers/gpu/drm/drm_fb_helper.c
> index af1fe79c701d..13095d38aa42 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -562,8 +562,12 @@ EXPORT_SYMBOL(drm_fb_helper_release_info);
>   */
>  void drm_fb_helper_unregister_info(struct drm_fb_helper *fb_helper)
>  {
> -	if (fb_helper && fb_helper->info)
> -		unregister_framebuffer(fb_helper->info);
I'm not sure if we can assume these won't be NULL... AFAICT some drivers
still have their own struct drm_client_funcs vtable and could potentially
pass a NULL struct drm_fb_helper ?

If you think that's safe to do this and the function semantics should be
changed, then I think that the kernel-doc needs to be updated:

- * @fb_helper: driver-allocated fbdev helper, can be NULL
+ * @fb_helper: driver-allocated fbdev helper, must not be NULL

Other than that, the patch looks good to me:

Reviewed-by: Javier Martinez Canillas <javierm at redhat.com>

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat

Hi Javier

Am 03.09.24 um 12:18 schrieb Javier Martinez Canillas:
> Thomas Zimmermann <tzimmermann at suse.de> writes:
>
> Hello Thomas,
>
>> Call vga_switcheroo_client_fb_set() with the PCI device from the
>> instance of struct fb_info. All fbdev clients now run these calls.
>> For non-PCI devices or drivers without vga-switcheroo, this does
>> nothing. For i915 and radeon, it allows these drivers to use a
>> common fbdev client.
>>
>> The device is the same as the one stored in struct drm_client and
>> struct drm_fb_helper, so there is no difference in behavior. Some
>> NULL-pointer checks are being removed, where those pointers cannot
>> be NULL.
>>
>> Signed-off-by: Thomas Zimmermann <tzimmermann at suse.de>
>> ---
>>   drivers/gpu/drm/drm_fb_helper.c | 15 +++++++++++----
>>   1 file changed, 11 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/drm_fb_helper.c
b/drivers/gpu/drm/drm_fb_helper.c
>> index af1fe79c701d..13095d38aa42 100644
>> --- a/drivers/gpu/drm/drm_fb_helper.c
>> +++ b/drivers/gpu/drm/drm_fb_helper.c
>> @@ -562,8 +562,12 @@ EXPORT_SYMBOL(drm_fb_helper_release_info);
>>    */
>>   void drm_fb_helper_unregister_info(struct drm_fb_helper *fb_helper)
>>   {
>> -	if (fb_helper && fb_helper->info)
>> -		unregister_framebuffer(fb_helper->info);
> I'm not sure if we can assume these won't be NULL... AFAICT some
drivers
> still have their own struct drm_client_funcs vtable and could potentially
> pass a NULL struct drm_fb_helper ?
I did a

 ? git grep -B4 drm_fb_helper_unregister_info

on drm-tip and all callers, such as [1], test fb_helper->info before 
calling the function. So it's safe to remove the test.

[1] 
https://elixir.bootlin.com/linux/v6.10/source/drivers/gpu/drm/drm_fbdev_dma.c#L162
>
> If you think that's safe to do this and the function semantics should
be
> changed, then I think that the kernel-doc needs to be updated:
>
> - * @fb_helper: driver-allocated fbdev helper, can be NULL
> + * @fb_helper: driver-allocated fbdev helper, must not be NULL
Ok.
>
> Other than that, the patch looks good to me:
>
> Reviewed-by: Javier Martinez Canillas <javierm at redhat.com>
Thanks.

Best regards
Thomas
>
-- 
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)