Re: [PATCH v3 00/21] drm: Add support for bus-format negotiation

[Ezequiel Garcia <ezequiel@collabora.com>]

Hi Boris, Neil,

On Wed, 2019-10-23 at 17:44 +0200, Boris Brezillon wrote:
> This patch series aims at adding support for runtime bus-format
> negotiation between all elements of the
> 'encoder -> bridges -> connector/display' section of the pipeline.
> 
> In order to support that, we need drm bridges to fully take part in the
> atomic state validation process, which requires adding a
> drm_bridge_state and a new drm_bridge_funcs.atomic_check() hook.
> Once those basic building blocks are in place, we can add new hooks to
> allow bus format negotiation (those are called just before
> ->atomic_check()). The bus format selection is done at runtime by
> testing all possible combinations across the whole bridge chain until
> one is reported to work.
> 
> Major changes since v2:
> * Get rid of the dummy bridge embedded in drm_encoder and let encoder
>   drivers provide their own bridge element
> * Clarify APIs and improve the doc
> * Propagate bus flags by default
> 
> Major changes since the RFC:
> 
> * Add a dummy bridge to the drm_encoder object so that vc4 and exynos
>   DSI drivers can implement the pre_enable/post_disable hooks instead
>   of manually setting encoder->bridge to NULL to control the
>   enable/disable sequence. This change is also a first step towards
>   drm_bridge/drm_encoder unification. New encoder drivers should
>   stop implementing drm_encoder_helper_funcs and switch to
>   drm_bridge_funcs. Existing drivers can be converted progressively
>   (already have a branch where I started converting some of them [1])
> * rework the bus format negotiation to give more control to bridge
>   drivers in the selection process (driver can select at runtime which
>   input bus format they support for a specific output bus format based
>   on any information available in the connector, crtc and bridge state.
> 
> A more detailed changelog is provided in each patch.
> 
> This patch series is also available here [2].
> 
> Thanks,
> 
> Boris
> 
> [1]https://github.com/bbrezillon/linux-0day/commits/drm-encoder-bridge
> [2]https://github.com/bbrezillon/linux-0day/commits/drm-bridge-busfmt-v3
> 
> *** BLURB HERE ***
> 
> Boris Brezillon (21):
>   drm/vc4: Declare the DSI encoder as a bridge element
>   drm/exynos: Don't reset bridge->next
>   drm/exynos: Declare the DSI encoder as a bridge element
>   drm/bridge: Rename bridge helpers targeting a bridge chain
>   drm/bridge: Introduce drm_bridge_chain_get_next_bridge()
>   drm: Stop accessing encoder->bridge directly

Patches 1 to 6 seem to be reviewed, and appear as a good
step forward.

Perhaps we can consider merging these first? That way,
we can reduce the patches needed to rebase and submit
on each iteration.

Regards,
Ezequiel