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

[Thomas Zimmermann <tzimmermann@suse.de>]

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Hi

Am 06.11.21 um 22:02 schrieb Sven Schnelle:
> Thomas Zimmermann <tzimmermann@suse.de> writes:
> 
>> Hi
>>
>> Am 01.11.21 um 09:54 schrieb Sven Schnelle:
>>> Hi Thomas,
>>> Thomas Zimmermann <tzimmermann@suse.de> writes:
>>> 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]
> 
> I have converted the driver, 

Cool!

> but am using FORMAT_C8 because i haven't
> figured out yet how to switch the card to XRGB8888. That's still on the
> TODO list.

Don't worry. As I outlined , you can still convert any image from 
XRGB888 to RGB332 and display this instead.

> 
> One question about hw blitting: with the old fbdev framework one could
> replace the fb_imageblit function. For normal console text, this
> function gets called with a monochrome bitmap, and an fg/bg color value.
> This makes it easy to use HW accelerated blitting for text. In the
> gpu/drm drivers i think i found only one driver (nouveau) doing this and
> that was via the drm fbdev layer.
> 
> Is that still the way to go, or is there a better way to do HW accelerated
> text blitting?

Simply call drm_fbdev_generic_setup() after registering the device. This 
should give you a console.

Don't bother about HW-accelerated blitting. From what I've heard, it 
barely makes a difference nowadays. And our generic helpers have plenty 
of features. Not using them to get a small benefit from HW blitting 
isn't worth it.

Best regards
Thomas

> 
> Thanks
> 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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