Re: [PATCH] drm/tegra: Remove existing framebuffer only if we support display

[Javier Martinez Canillas <javierm@redhat.com>]

Thierry Reding <thierry.reding@gmail.com> writes:

Hello Thierry,

> On Wed, Aug 30, 2023 at 08:13:04AM +0200, Javier Martinez Canillas wrote:

[...]

>> I also wonder if is worth to move the drm_num_crtcs() function from
>> drivers/gpu/drm/drm_crtc.c to include/drm/drm_crtc.h and use that helper
>> instead?
>
> I've been looking at this, there's a few things that come to mind. It
> seems like we have a couple of different ways to get the number of CRTCs
> for a device. We have struct drm_device's num_crtcs, which is set during
> drm_vblank_init(), then we have struct drm_mode_config's num_crtc, which
> is incremented every time a new CRTC is added (and decremented when a
> CRTC is removed), and finally we've got the drm_num_crtcs() which
> "computes" the number of CRTCs registered by iterating over all CRTCs
> that have been registered.
>
> Are there any cases where these three can yield different values? Would
> it not make sense to consolidate these into a single variable?
>

I als was confused by that when looked at the implementation of the
mentioned helpers and couldn't find a reason why there are different
ways to calculate the number of CRTCs.

Maybe Sima or someone else can shed some light?

> Thierry

-- 
Best regards,

Javier Martinez Canillas
Core Platforms
Red Hat