Re: [PATCH/RFT] fbdev driver for HP Visualize FX cards

From: Thomas Zimmermann <tzimmermann@suse.de>
To: Sven Schnelle <svens@stackframe.org>
Cc: linux-fbdev@vger.kernel.org,
	dri-devel <dri-devel@lists.freedesktop.org>,
	linux-parisc@vger.kernel.org, Helge Deller <deller@gmx.de>
Subject: Re: [PATCH/RFT] fbdev driver for HP Visualize FX cards
Date: Mon, 1 Nov 2021 10:33:12 +0100	[thread overview]
Message-ID: <e21cdf83-2178-7c59-2585-a6012f861f68@suse.de> (raw)
In-Reply-To: <87r1c0s1bt.fsf@x1.stackframe.org>

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Hi

Am 01.11.21 um 09:54 schrieb Sven Schnelle:
> Hi Thomas,
> 
> Thomas Zimmermann <tzimmermann@suse.de> writes:
> 
>> Am 31.10.21 um 20:53 schrieb Sven Schnelle:
>>> Hi List(s),
>>> i wrote a fbdev driver for the HP Visualize FX cards used some of
>>> the
>>> PA-RISC workstations. It utilizes some of the 2D acceleration features
>>> present in the card.
>>> [..]
>>
>> Thanks for all the work you put into this. We welcome drivers even for
>> older hardware, but not for fbdev. DRM is all the rage now and has
>> been for a while. I'd like to ask you to convert the driver to DRM and
>> resubmit to <dri-devel@lists.freedesktop.org>.
>>
>> I while ago, I made conversion helpers for this. You can look at [1]
>> for a trivial DRM drivers that wraps existing fbdev drivers for use
>> with DRM. Once you have that, it turns into a refactoring job.
> 
> Thanks, i wasn't aware as i normally don't do any graphics related
> development. I take a look at dri and port the driver, which is
> hopefully not too hard.

Sounds good.

The one big difference when converting is that DRM really wants drivers 
to support 32-bit XRGB colors. It's not a DRM limitation per se, but a 
requirement of today's userspace programs. AFAICS your fbdev driver uses 
a 256-color palette format. So the DRM driver would have to convert
XRGB8888 to 8-bit RGB332 and install a corresponding palette. Don't 
worry, it's easy. Take a look at the cirrus driver for a simple DRM 
driver. [1]

If you need help, there's <dri-devel@lists.freedesktop.org>.

Best regards
Thomas

[1] 
https://elixir.bootlin.com/linux/latest/source/drivers/gpu/drm/tiny/cirrus.c

> 
> Sven
> 

-- 
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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