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

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Message-ID: <85308177b3679d1103feee7a2b6e5879@agner.ch>
Date:   Mon, 18 Jun 2018 10:13:16 +0200
From:   Stefan Agner <stefan@...er.ch>
To:     Marek Vasut <marek.vasut@...il.com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sascha Hauer <s.hauer@...gutronix.de>
Cc:     Leonard Crestez <leonard.crestez@....com>, festevam@...il.com,
        marex@...x.de, 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
Subject: Re: [PATCH 1/3] drm: mxsfb: Change driver.name to mxsfb-drm

On 18.06.2018 09:43, Daniel Vetter wrote:
> On Sat, Jun 16, 2018 at 01:32:44AM +0200, 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.
> 
> Yeah agreed, imo the proper fix here would be to either update the dts for
> the affected boards and/or make mxsfb accept the old dt bindings for
> backwards compat. Artificially extending the life of the fbdev drivers
> seems silly.

We shouldn't have merged a DRM driver with a driver name which conflicts
with an existing driver... If anything, this is artificially shortening
the lifetime of the fbdev driver :-)

Again, I am ok with removing the driver. I just think it is silly to do
it just because of the conflicting driver name.

Maybe Sascha, original author of the mxs fbdev driver has an opinion on
this?

--
Stefan