linux-kernel - Re: [PATCH 8/8] drm/bridge: it66121: Allow link this driver as a lib

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Message-ID: <58d71614-4be0-4b78-8169-d7e6399734b3@linaro.org>
Date:   Mon, 20 Nov 2023 09:23:24 +0100
From:   Neil Armstrong <neil.armstrong@...aro.org>
To:     Sui Jingfeng <sui.jingfeng@...ux.dev>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     Phong LE <ple@...libre.com>, Maxime Ripard <mripard@...nel.org>,
        Sui Jingfeng <suijingfeng@...ngson.cn>,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Thomas Zimmermann <tzimmermann@...e.de>
Subject: Re: [PATCH 8/8] drm/bridge: it66121: Allow link this driver as a lib

On 17/11/2023 18:14, Sui Jingfeng wrote:
> Hi,
> 
> On 2023/11/17 17:03, Dmitry Baryshkov wrote:
>> On Fri, 17 Nov 2023 at 06:24, Sui Jingfeng <sui.jingfeng@...ux.dev> wrote:
>>> Hi,
>>>
>>> On 2023/11/16 23:23, Dmitry Baryshkov wrote:
>>>>>>> Then you will need some way (fwnode?) to
>>>>>>> discover the bridge chain. And at the last point you will get into the
>>>>>>> device data and/or properties business.
>>>>>>>
>>>>>> No, leave that chance to a more better programmer and forgive me please,
>>>>>> too difficult, I'm afraid of not able to solve. Thanks a lot for the
>>>>>> trust!
>>>>   From my point of view: no.
>>>
>>> I respect the fact that the community prefer generic mechanisms.
>>> If our approach is not what the community want, can I switch back
>>> to my previous solution? I can reduce the duplication of our
>>> localized it66121 driver to a minimal, rewrite it until it meets
>>> the community's requirement. I know our device looks weird and
>>> our approach is not elegant. But at the very least, we could not
>>> mess the community's design up by localize. Otherwise, I don't know
>>> what is the better approach to solve such a problem.
>>>
>>> Can I switch back or any other ideas?
>> I keep on repeating: create the i2c device from your root device
>> driver, which parses BIOS data.
>>
> This is not my own problems, currently it66121 (but not only) display bridge driver
> don't works on X86 either. What we are trying to do is to provide a generic, non-platform
> dependent solution. It is not only relevant to my driver. In fact, this series made
> no assumption which hardware/display controller will be the user.
> 
> I have investigated before respin this patch, there are other hardwares which
> ship the it66121 display bridge. For example, the Fresco Logic FL2000dx USB 3.0
> to VGA display adapter[1][2]. Even the windows have a driver.
> 
> [1] https://github.com/FrescoLogic/FL2000
> [2] https://oemdrivers.com/graphics-fresco-logic-fl2000

Switching to fwnodes, registering an i2c bus and generating fwnode data matching the
interconnect architecture is the way.

DRM Bridge transition to fwnode only should be done first, this will open bridge
to any architecture and device description (DT or ACPI).

Neil

>