AFBC versions modifiers

[Liviu Dudau]

On Thu, Feb 28, 2019 at 11:15:11AM +0100, Daniel Vetter wrote:
> On Wed, Feb 27, 2019 at 03:41:35PM +0000, Ayan Halder wrote:
> > Hi Neil,
> > 
> > AFBC 1.0 does not support (ignoring common prefix AFBC_FORMAT_MOD_) BLOCK_SIZE_32x8, BLOCK_SIZE_64x4, BLOCK_SIZE_32x8_64x4
> > CBR, TILED, SC, DB and BCH  modifiers.
> > 
> > AFBC 1.2 does not support BLOCK_SIZE_64x4, BLOCK_SIZE_32x8_64x4, DB and BCH modifiers.
> 
> Would be great to add that to kernel comments in drm_fourcc.h ...

Kind of ... :)

Like Ayan is saying, the numbers relate to the spec, not what silicon
vendors implement. AFBC defines a set of "compression parameters" (for
the lack of a better definition) and then various blocks implement the
parameters that they need. Some might only encode buffers, in which case
they will ignore or skip all the options related to decoding, but will
still claim to be compliant with AFBC 1.x.

The best way to look at AFBC from an implementation PoV is to look at
the modifiers and determine if they are supported by a certain silicon
IP or not. The fact that a given modifier has been introduced by AFBC
spec number 1.2 or 1.1 should not be relevant.

Best regards,
Liviu


> -Daniel
> 
> > 
> > Beyond that it's very hard to say. The AFBC version numbers refer to versions of the specification, but aren't very useful for describing the actual bitstream format.
> > To determine which modifiers _are_ supported, you will really need to get technical documentation from the SoC vendor
> > 
> > Regards,
> > Ayan Kumar Halder
> > 
> > ________________________________
> > From: Neil Armstrong <narmstrong at baylibre.com>
> > Sent: Tuesday, February 26, 2019 2:15 PM
> > To: Ayan Halder; Liviu Dudau
> > Cc: DRI Development
> > Subject: AFBC versions modifiers
> > 
> > Hi Ayan,
> > 
> > Could you help distinguish which are the AFBC modifiers for each version of AFBC ?
> > 
> > The Amlogic SoCs embeds an AFBC 1.0 compatible decoder, then the newer SoCs embeds an AFBC 1.2 decoder,
> > I assume the modifiers before the patch "drm/fourcc: Add modifier defininitions for AFBC 1.3" are
> > valid for AFBC 1.2, but what is the subset for 1.0 and 1.1 ?
> > 
> > Thanks,
> > Neil
> > 
> > --
> > Neil Armstrong
> > Embedded Linux Software Engineer
> > BayLibre - At the Heart of Embedded Linux
> > www.baylibre.com<http://www.baylibre.com>
> 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

-- 
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