From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1752585AbdK1SV3 (ORCPT <rfc822;w@1wt.eu>);
        Tue, 28 Nov 2017 13:21:29 -0500
Received: from mail-it0-f42.google.com ([209.85.214.42]:37926 "EHLO
        mail-it0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1751648AbdK1SV1 (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Tue, 28 Nov 2017 13:21:27 -0500
X-Google-Smtp-Source: AGs4zMZzTMUQJe2Pil0rUvhT4s1lLZxdiyhrbGnK1zl3geR2Zzf4NK7mJHfBF52eBX/bo6huKhrMtg==
Date: Tue, 28 Nov 2017 10:21:23 -0800
From: Brian Norris <briannorris@chromium.org>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: Archit Taneja <architt@codeaurora.org>,
        Andrzej Hajda <a.hajda@samsung.com>, David Airlie <airlied@linux.ie>,
        Yannick Fertre <yannick.fertre@st.com>,
        Philippe Cornu <philippe.cornu@st.com>,
        Benjamin Gaignard <benjamin.gaignard@linaro.org>,
        Vincent Abriou <vincent.abriou@st.com>,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        Sean Paul <seanpaul@chromium.org>,
        Nickey Yang <nickey.yang@rock-chips.com>, hl@rock-chips.com,
        linux-rockchip@lists.infradead.org, mka@chromium.org,
        Jeffy Chen <jeffy.chen@rock-chips.com>,
        Doug Anderson <dianders@chromium.org>
Subject: Re: [PATCH] drm/bridge/synopsis: stop clobbering drvdata
Message-ID: <20171128182121.GA116479@google.com>
References: <20171128010538.119114-1-briannorris@chromium.org>
 <1743921.AofnJoQ8Rz@avalon>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1743921.AofnJoQ8Rz@avalon>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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