linux-kernel - Re: [RFC PATCH 1/8] drm: writeback: Refactor drm_writeback

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Message-ID: <20250813120029.GE20174@pendragon.ideasonboard.com>
Date: Wed, 13 Aug 2025 15:00:29 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: "Kandpal, Suraj" <suraj.kandpal@...el.com>
Cc: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>,
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Subject: Re: [RFC PATCH 1/8] drm: writeback: Refactor drm_writeback_connector
 structure

On Wed, Aug 13, 2025 at 10:04:22AM +0000, Kandpal, Suraj wrote:
> > > > };
> > >
> > > I still don't like that. This really doesn't belong here. If anything,
> > > the drm_connector for writeback belongs to drm_crtc.
> > 
> > Why? We already have generic HDMI field inside drm_connector. I am really
> > hoping to be able to land DP parts next to it. In theory we can have a DVI-
> > specific entry there (e.g. with the subconnector type).
> > The idea is not to limit how the drivers subclass those structures.
> > 
> > I don't see a good case why WB should deviate from that design.
> > 
> > > If the issue is that some drivers need a custom drm_connector
> > > subclass, then I'd rather turn the connector field of
> > > drm_writeback_connector into a pointer.
> > 
> > Having a pointer requires additional ops in order to get drm_connector from
> > WB code and vice versa. Having drm_connector_wb inside drm_connector
> > saves us from those ops (which don't manifest for any other kind of structure).
> > Nor will it take any more space since union will reuse space already taken up by
> > HDMI part.
> 
> Seems like this thread has died. We need to get a conclusion on the design.
> Laurent do you have any issue with the design given Dmitry's explanation as to why this
> Design is good for drm_writeback_connector.

I'm busy, I'll try to reply in the next few days.

> > > > I plan to add drm_connector_dp in a similar way, covering DP needs
> > > > (currently WIP).

-- 
Regards,

Laurent Pinchart