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Date:   Thu, 20 Jun 2019 23:12:04 +0200
From:   Daniel Vetter <daniel@ffwll.ch>
To:     Cheng-yi Chiang <cychiang@chromium.org>
Cc:     Hans Verkuil <hverkuil@xs4all.nl>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Philipp Zabel <p.zabel@pengutronix.de>,
        Mark Brown <broonie@kernel.org>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Takashi Iwai <tiwai@suse.com>,
        Jaroslav Kysela <perex@perex.cz>,
        Russell King <rmk+kernel@armlinux.org.uk>,
        Andrzej Hajda <a.hajda@samsung.com>,
        Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
        David Airlie <airlied@linux.ie>,
        Rob Herring <robh+dt@kernel.org>,
        Heiko Stuebner <heiko@sntech.de>,
        Doug Anderson <dianders@chromium.org>,
        Dylan Reid <dgreid@chromium.org>, tzungbi@chromium.org,
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        Dariusz Marcinkiewicz <darekm@google.com>,
        Daniel Vetter <daniel@ffwll.ch>
Subject: Re: [PATCH 1/7] video: add HDMI state notifier support
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Massively cutting this thread, since halfway through in my previous reply
I realized that maybe hdmi_codec is a much better starting point.

On Thu, Jun 20, 2019 at 09:23:23PM +0800, Cheng-yi Chiang wrote:
> On Thu, Jun 20, 2019 at 5:25 PM Daniel Vetter <daniel@ffwll.ch> wrote:
> > Yeah fully agreeing that hdmi_audio_code is probably a better starting
> > point. Problem is that becuase hdmi_codec is built on top of platform
> > device it's quite a bit harder to extend with callbacks and things like
> > that, without breaking the driver model.
> >
> > I need to think about this more, but if all we need to look at is
> > hdmi_codec, then I think this becomes a lot easier. And we can ignore
> > drm_audio_component.h completely.
> 
> 
> It is surprising that you think this way.
> Maybe the original patch before hdmi-notifier was introduced is the
> better way to solve this issue, if we only need to look at hdmi_codec.
> 
> The history of hdmi_codec driver is in this patch series:
> 
> https://lore.kernel.org/patchwork/patch/539656/

Hm, this doesn't seem to be the hdmi_codec driver I meant, but another,
new one. I was talking about SND_SOC_HDMI_CODEC.

> There was a callback mechanism implemented between dw-hdmi and hdmi
> codec driver.
> It was later consolidated by Doug in this patch for better jack status
> reporting:
> 
> https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/303573/

Hm that still seems entirely separate hdmi-codec specific to dw-hdmi only
...

> I am not sure why the original patch series did not get fully accepted
> in the upstream.
> It was quite long time ago.
> 
> But if you think this might be the right way to do, then it is even
> better for us because the patch series and Doug's patch had been quite
> stable
> on our RK3288 products for about four years with plenty of users, so
> we have much higher confidence in them.
> I can rebase and clean up them and post another patch for review.
> 
> Please let me know what approach you feel is better.
> Thanks again!

Not sure we're talking about the same. What I had in mind is to add jack
status to the hdmi-codec.c stuff, which is used by multiple soc drm
display drivers already. Looking at git grep output, there seems to be
already some support for dw-hdmi synopsys drm_bridge driver. I thought of
extending that. Does that not work for you?

Thanks, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch