linux-kernel - Re: [PATCH v1 0/4] fbtft: Unorphan the driver for maintenance

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Date:   Wed, 26 Jan 2022 12:41:41 +0100
From:   Thomas Zimmermann <tzimmermann@...e.de>
To:     Helge Deller <deller@....de>,
        Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Phillip Potter <phil@...lpotter.co.uk>,
        Lee Jones <lee.jones@...aro.org>,
        Heiner Kallweit <hkallweit1@...il.com>,
        Carlis <zhangxuezhi1@...ong.com>, linux-kernel@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-fbdev@...r.kernel.org,
        dri-devel@...ts.freedesktop.org,
        Michael Hennerich <michael.hennerich@...log.com>,
        Andy Shevchenko <andy@...nel.org>
Subject: Re: [PATCH v1 0/4] fbtft: Unorphan the driver for maintenance

Hi

Am 26.01.22 um 11:59 schrieb Helge Deller:
> On 1/26/22 11:02, Andy Shevchenko wrote:
>> On Wed, Jan 26, 2022 at 10:52 AM Thomas Zimmermann <tzimmermann@...e.de> wrote:
>>> Am 25.01.22 um 21:21 schrieb Andy Shevchenko:
>>>> Since we got a maintainer for fbdev, I would like to
>>>> unorphan fbtft (with the idea of sending PRs to Helge)
>>>> and move it out of staging since there is no more clean
>>>> up work expected and no more drivers either.
>>>>
>>>> Thoughts?
> 
> Personally I'm in favour of this proposal and would be happy
> to take patches for it through the fbdev git tree.
> Reasoning below...
> 
>>> But why? We already have DRM drivers for some of these devices.
>>
>> No, we do not (only a few are available).
> 
> seems to be 2 out of 10 (according to the other mails)

FYI it's ili9163 and hx8357d. Both of those are of the same size ('wc 
-l') on DRM and fbdev: 200 to 300 loc.

>>> Porting the others to DRM is such a better long-term plan.  OTOH,
>>> as no one has shown up and converted them, maybe they should be
>>> left dead or removed entirely.
>>
>> As I mentioned above there are devices that nobody will take time to
>> port to a way too complex DRM subsystem. But the devices are cheap and
>> quite widespread in the embedded world. I'm in possession of 3 or 4
>> different models and only 1 is supported by tiny DRM.
>>
>> On top of that the subtle fact people forgot about FBTFT is that it
>> does support parallel interface (yes, I know that it's not performant,
>> but one of the displays I have is with that type of interface).
> 
> I don't know those devices, but it seems they are still being used.
> 
> And the reasons why they have not been ported to DRM yet is
> likely because either lack of man-power, a slow-down with DRM (due to
> slow bus connections or increased memory usage with DRM), or
> simply that it's used in embedded-like scenarios with a limited
> set of userspace applications for which existing fbdev access is sufficient.
> 
> Again, I don't know the reason for this specific devices, but I know
> of other devices for which those reasons above are valid.
> Just the example I posted yesterday where a simple "time dmesg" needed
> unaccelerated 19 seconds compared to 2 seconds with acceleration.
> So, as long as acceleration isn't possible with that driver in
> DRM, DRM isn't a preferred target where the driver should be ported.
> 
> So, I'd be fine to take it into fbdev tree.
> 
> Interestingly there is another fbdev driver in staging (sm750fb) with
> similiar issues. The TODO mentions a porting to DRM which happens at
> https://gitlab.com/sudipm/sm750/tree/sm750
> but the last commit there is 3 years ago. I don't know why it wasn't
> continued yet.

It's always for the same reason: the hw is old and devs have moved on.

Best regards
Thomas

-- 
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev

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