+everyone again On Tue, Sep 4, 2018 at 2:39 PM Bas Nieuwenhuizen bas@basnieuwenhuizen.nl wrote:

On Tue, Sep 4, 2018 at 2:22 PM Daniel Stone daniel@fooishbar.org wrote:

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Hi,

On Tue, 4 Sep 2018 at 11:44, Christian König ckoenig.leichtzumerken@gmail.com wrote:

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Am 04.09.2018 um 12:15 schrieb Daniel Stone:

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Right. The conclusion, after people went through and started sorting out the kinds of formats for which they would _actually_ export real colour buffers for, that most vendors definitely have fewer than 115,792,089,237,316,195,423,570,985,008,687,907,853,269,984,665,640,564,039,457,584,007,913,129,639,936 possible formats to represent, very likely fewer than 340,282,366,920,938,463,463,374,607,431,768,211,456 formats, probably fewer than 72,057,594,037,927,936 formats, and even still generally fewer than 281,474,976,710,656 if you want to be generous and leave 8 bits of the 56 available.

The problem here is that at least for some parameters we actually don't know which formats are actually used.

The following are not real world examples, but just to explain the general problem.

The memory configuration for example can be not ASIC specific, but rather determined by whoever took the ASIC and glued it together with VRAM on a board. It is not likely that somebody puts all the VRAM chips on one channel, but it is still perfectly possible.

Same is true for things like harvesting, e.g. of 16 channels halve of them could be bad and we need to know which to actually use.

Sure, that's fine, but I'm not sure why, for instance, 'half of the memory channels are bad and must be avoided' would be attached to a format in the same way that macrotile size/depth would be? Similarly, what happens if you encode a channel or lane blacklist mask into a modifier, and then you import a buffer with that modifier into a client API on another device. Does that also apply to the other device or only the source device?

How then do you handle the capability query between them: is it relevant to device B attempting to import and sample from an image that device A only has a 128-bit memory bus because of SKU configuration? How does generic userspace look at a token which encodes all of this information and know that the buffer is interchangeable between devices?

So my idea here is to encode all the bits that determine format in a way that as much as possible if it results in the same layout it should get the same modifier(i.e. remove useless info):

https://lists.freedesktop.org/archives/dri-devel/2018-September/188418.html

An example of the per-chip things is the PIPE_CONFIG, which is used for address calculation in the macro-tiled mode:

https://gitlab.freedesktop.org/mesa/mesa/blob/master/src/amd/addrlib/r800/si...

two chips with different PIPE_CONFIG will have different texture layouts, as the address swizzles are different.

So it gets included in the modifier (the PIPE_CONFIG is pretty much constant per chip but multiple chips might have the same PIPE_CONFIG).

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Cheers, Daniel _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel