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[209.85.210.48]) by smtp.gmail.com with ESMTPSA id w85sm77754oif.42.2021.05.03.09.55.44 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 May 2021 09:55:44 -0700 (PDT) Received: by mail-ot1-f48.google.com with SMTP id 65-20020a9d03470000b02902808b4aec6dso5674063otv.6 for ; Mon, 03 May 2021 09:55:44 -0700 (PDT) X-Received: by 2002:a25:d9ce:: with SMTP id q197mr15755336ybg.276.1620060932851; Mon, 03 May 2021 09:55:32 -0700 (PDT) MIME-Version: 1.0 References: <20210423165906.2504169-1-dianders@chromium.org> <20210423095743.v5.9.I3e68fa38c4ccbdbdf145cad2b01e83a1e5eac302@changeid> In-Reply-To: From: Doug Anderson Date: Mon, 3 May 2021 09:55:20 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH v5 09/20] drm/bridge: ti-sn65dsi86: Break GPIO and MIPI-to-eDP bridge into sub-drivers To: Linus Walleij Cc: Andrzej Hajda , Neil Armstrong , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Sam Ravnborg , Wolfram Sang , MSM , Rob Clark , Stanislav Lisovskiy , Stephen Boyd , Steev Klimaszewski , Maarten Lankhorst , linux-i2c , Bjorn Andersson , "open list:DRM PANEL DRIVERS" , Daniel Vetter , David Airlie , Robert Foss , linux-kernel Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Sat, May 1, 2021 at 4:59 AM Linus Walleij wrote: > > On Fri, Apr 23, 2021 at 6:59 PM Douglas Anderson wrote: > > > Let's use the newly minted aux bus to break up the driver into sub > > drivers. We're not doing a full breakup here: all the code is still in > > the same file and remains largely untouched. The big goal here of > > using sub-drivers is to allow part of our code to finish probing even > > if some other code needs to defer. This can solve some chicken-and-egg > > problems. Specifically: > > - In commit 48834e6084f1 ("drm/panel-simple: Support hpd-gpios for > > delaying prepare()") we had to add a bit of a hack to simpel-panel > > to support HPD showing up late. We can get rid of that hack now > > since the GPIO part of our driver can finish probing early. > > - We have a desire to expose our DDC bus to simple-panel (and perhaps > > to a backlight driver?). That will end up with the same > > chicken-and-egg problem. A future patch to move this to a sub-driver > > will fix it. > > - If/when we support the PWM functionality present in the bridge chip > > for a backlight we'll end up with another chicken-and-egg > > problem. If we allow the PWM to be a sub-driver too then it solves > > this problem. > > > > Signed-off-by: Douglas Anderson > > --- > > > > Changes in v5: > > - Fix module compile problems (Bjorn + kbuild bot) > > - Remove useless MODULE_DEVICE_TABLE (Bjorn). > > This is generally a good idea. I have no idea when to use > auxbus or MFD It was a bit hard for me to figure out too. I think historically this could have been implemented by MFD but I believe that the point of introducing the AUX bus was that MFD wasn't a great fit for things like this. It's talked about a bit in "Documentation/driver-api/auxiliary_bus.rst". For me the important thing here is that we think of the bridge chip as one device, not a collection of IP blocks glued together in one package. As some evidence, the DT bindings don't have sub-nodes for this. There's a single DT node that says that this one device is the bridge, is a GPIO controller, and can provide a PWM. > but I trust that you researched that so: > Acked-by: Linus Walleij Thanks! I'll land it then to whittle the patch stack down to just the controversial EDID one. -Doug