Re: [PATCH v5 15/21] drm/tegra: Add new UAPI to header

Dmitry Osipenko
2021-01-13T18:15:05Z

11.01.2021 16:00, Mikko Perttunen пишет:
> +struct drm_tegra_submit_buf {
> + /**
> + * @mapping_id: [in]
> + *
> + * Identifier of the mapping to use in the submission.
> + */
> + __u32 mapping_id;

I'm now in process of trying out the UAPI using grate drivers and this
becomes the first obstacle.

Looks like this is not going to work well for older Tegra SoCs, in
particular for T20, which has a small GART.

Given that the usefulness of the partial mapping feature is very
questionable until it will be proven with a real userspace, we should
start with a dynamic mappings that are done at a time of job submission.

DRM already should have everything necessary for creating and managing
caches of mappings, grate kernel driver has been using drm_mm_scan for a
long time now for that.

It should be fine to support the static mapping feature, but it should
be done separately with the drm_mm integration, IMO.

What do think?