Re: [PATCH] drm/bridge/synopsis: stop clobbering drvdata

From: Brian Norris <briannorris@chromium.org>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Doug Anderson <dianders@chromium.org>,
	hl@rock-chips.com, linux-rockchip@lists.infradead.org,
	David Airlie <airlied@linux.ie>,
	Jeffy Chen <jeffy.chen@rock-chips.com>,
	Philippe Cornu <philippe.cornu@st.com>,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
	Yannick Fertre <yannick.fertre@st.com>,
	Nickey Yang <nickey.yang@rock-chips.com>,
	mka@chromium.org, Vincent Abriou <vincent.abriou@st.com>
Subject: Re: [PATCH] drm/bridge/synopsis: stop clobbering drvdata
Date: Tue, 28 Nov 2017 10:21:23 -0800	[thread overview]
Message-ID: <20171128182121.GA116479@google.com> (raw)
In-Reply-To: <1743921.AofnJoQ8Rz@avalon>

Hi Laurent,

On Tue, Nov 28, 2017 at 02:51:46PM +0200, Laurent Pinchart wrote:
> Hi Brian,
> 
> Thank you for the patch.
> 
> I'd mention dw-mipi-dsi in the subject line as the directory contains the dw-
> hdmi driver as well that this patch doesn't touch.

Yep. Does it need another tag in the subject? e.g., '.../dw-mipi-dsi:'?

> On Tuesday, 28 November 2017 03:05:38 EET Brian Norris wrote:
> > Bridge drivers/helpers shouldn't be clobbering the drvdata, since a
> > parent driver might need to own this.
> 
> By parent driver I assume you mean a glue driver that binds to the SoC-
> specific compatible string for the DSI transmitter.

Indeed. Nickey picked this up for his Rockchip driver submission, but
maybe we should reword the commit message a bit.

> > Instead, let's return our
> > 'dw_mipi_dsi' object and have callers pass that back to us for removal.
> > 
> > Signed-off-by: Brian Norris <briannorris@chromium.org>
> 
> Wouldn't it be cleaner to embed the dw_mipi_dsi structure in the parent-
> specific data structure (struct dw_mipi_dsi_stm and struct 
> dw_mipi_dsi_rockchip when the "[PATCH v3 0/5] Update ROCKCHIP DSI driver that 
> uses dw-mipi-dsi bridge" patch series will land) instead of allocating it 
> dynamically ? We would then have a single object to track.

I suppose we could do that too. But that would require exposing the
whole layout of 'struct dw_mipi_dsi' to users. Do we want to sacrifice
the enforced separation for a little bit of nicer object handling?

Also, this was modeled a bit after the similar rework needed to untangle
the drvdata handling in the Rockchip analogix DP driver vs. the analogix
bridge DP code:

[PATCH v6 03/10] drm/bridge: analogix: Do not use device's drvdata
https://patchwork.kernel.org/patch/10015875/

Brian
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