linux-kernel - Re: [PATCH 1/3] drm: mxsfb: Change driver.name to mxsfb-drm

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Message-ID: <6fdba55b-0be6-9e28-d87a-43d876a1fd09@denx.de>
Date:   Tue, 10 Jul 2018 11:11:17 +0200
From:   Marek Vasut <marex@...x.de>
To:     Stefan Agner <stefan@...er.ch>, Marek Vasut <marek.vasut@...il.com>
Cc:     Leonard Crestez <leonard.crestez@....com>, festevam@...il.com,
        shawnguo@...nel.org, devicetree@...r.kernel.org,
        linux-fbdev@...r.kernel.org, marcofrk@...il.com,
        linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        dl-linux-imx <linux-imx@....com>, kernel@...gutronix.de,
        Fabio Estevam <fabio.estevam@....com>,
        linux-arm-kernel@...ts.infradead.org, l.stach@...gutronix.de
Subject: Re: [PATCH 1/3] drm: mxsfb: Change driver.name to mxsfb-drm

On 07/10/2018 11:06 AM, Stefan Agner wrote:
> On 16.06.2018 01:32, Marek Vasut wrote:
>> On 06/16/2018 12:42 AM, Leonard Crestez wrote:
>>> On Fri, 2018-06-15 at 23:36 +0200, Marek Vasut wrote:
>>>> On 06/15/2018 10:58 PM, Leonard Crestez wrote:
>>>>> On Fri, 2018-06-15 at 16:47 -0300, Fabio Estevam wrote:
>>>>>> On Fri, Jun 15, 2018 at 4:43 PM, Leonard Crestez
>>>>>> <leonard.crestez@....com> wrote:
>>>
>>>>>>> The FBDEV driver uses the same name and both can't be registered at the
>>>>>>> same time. Fix this by renaming the drm driver to mxsfb-drm
>>>>>>
>>>>>> Stefan sent the same patch a few days ago:
>>>>>
>>>>> In that thread there is a proposal for removing the old fbdev/mxsfb
>>>>> driver entirely.
>>>>>
>>>>> That would break old DTBs, isn't this generally considered bad? Also,
>>>>> are we sure the removal of fbdev/mxsfb wouldn't lose any features?
>>>>>
>>>>> What my series does is make both drivers work with the same kernel
>>>>> image and turns the choice into a board-level dtb decision. Supporting
>>>>> everything at once seems desirable to me and it allows for a very
>>>>> smooth upgrade path.
>>>>
>>>> Having two drivers in the kernel with different set of bugs is always bad.
>>>>
>>>>> The old driver could be removed later, after all users are converted.
>>>>
>>>> Both drivers were in for long enough already. And let's be realistic,
>>>> how many MX23/MX28 users of old DTs with new kernels are there who
>>>> cannot update the DT as well ?
>>>
>>> Grepping for "display =" in arch/arm/boot/dts/imx* I see that old
>>> bindings are also used by 3rd-party boards for imx6/7:
>>>  * imx6sx-nitrogen6sx
>>>  * imx6ul-geam
>>>  * imx6ul-isiot
>>>  * imx6ul-opos6uldev
>>>  * imx6ul-pico-hobbit
>>>  * imx6ul-tx6ul
>>>  * imx7d-nitrogen7
>>
>> Er, yes, a handful of boards which could be updated :)
>>
>>> Converting everything might be quite a bit of work, and explicitly
>>> supporting old bindings is also work.
>>
>> Does adding support for old bindings justify the effort invested ? I
>> doubt so, it only adds more code to maintain.
>>
>>> It is very confusing that there is a whole set of displays for imx6/7
>>> which are supported by upstream but only with a non-default config.
>>> While it is extremely common in the embedded field to have custom
>>> configs the default one in the kernel should try to "just work".
>>>
>>> Couldn't this patch series be considered a bugfix? It was also
>>> surprisingly small.
>>
>> I think it's just a workaround which allows you to postpone the real
>> fix, and I don't like that.
> 
> This is one of the situation where states quo is kinda the worst
> situation.
> 
> Currently imx_v6_v7_defconfig and mxs_defconfig actually still uses
> CONFIG_FB_MXS.
> 
> I understand that you'd rather prefer to move forward. I suggest we do
> it in steps.
> 
> In 4.19:
> 
> - Change DRM driver.name to mxsfb-drm so we avoid conflicts for now

But this will break mesa if it depends on mxsfb name for ie. etnaviv
binding.

> - Remove CONFIG_FB_MXS from imx_v6_v7_defconfig/mxs_defconfig now, and
> only enable CONFIG_DRM_MXSFB=y
> - Add (deprecated) to CONFIG_FB_MXS
> 
> In 4.19/4.20:
> - Fix the above device trees
> 
> In 4.20/4.21:
> - Remove FB_MXS
> 
> Does that sound reasonable? If yes, I can send the patch set to do step
> 1.

Can you fix the DTs for 4.19 too ?

-- 
Best regards,
Marek Vasut