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Date:   Thu, 12 Jul 2018 11:21:57 +0200
From:   Stefan Agner <stefan@agner.ch>
To:     Marek Vasut <marex@denx.de>
Cc:     Marek Vasut <marek.vasut@gmail.com>,
        Leonard Crestez <leonard.crestez@nxp.com>, festevam@gmail.com,
        shawnguo@kernel.org, devicetree@vger.kernel.org,
        linux-fbdev@vger.kernel.org, marcofrk@gmail.com,
        linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
        dl-linux-imx <linux-imx@nxp.com>, kernel@pengutronix.de,
        Fabio Estevam <fabio.estevam@nxp.com>,
        linux-arm-kernel@lists.infradead.org, l.stach@pengutronix.de
Subject: Re: [PATCH 1/3] drm: mxsfb: Change driver.name to mxsfb-drm
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On 10.07.2018 11:11, Marek Vasut wrote:
> 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@nxp.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.
> 

Does it? grep -r -e mxsfb in libdrm and mesa master returns nothing.

There is also .name in struct drm_driver, which is already set to
mxsfb-drm... Is that the one exposed to user space?

>> - 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 ?

Getting tight, but will try.

--
Stefan