[Mesa-dev] [PATCH-RFC] i965: do not advertise MESA_FORMAT_Z_UNORM16 support

[Eric Anholt]

Kenneth Graunke <kenneth at whitecape.org> writes:

> On 02/18/2014 09:48 PM, Chia-I Wu wrote:
>> Since 73bc6061f5c3b6a3bb7a8114bb2e1ab77d23cfdb, Z16 support is not advertised
>> for OpenGL ES contexts due to the terrible performance.  It is still enabled
>> for desktop GL because it was believed GL 3.0+ requires Z16.
>> 
>> It turns out only GL 3.0 requires Z16, and that is corrected in later GL
>> versions.  In light of that, and per Ian's suggestion, stop advertising Z16
>> support by default, and add a drirc option, gl30_sized_format_rules, so that
>> users can override.
>
> I actually don't think that GL 3.0 requires Z16, either.
>
> In glspec30.20080923.pdf, page 180, it says:
> "[...] memory allocation per texture component is assigned by the GL to
> match the allocations listed in tables 3.16-3.18 as closely as possible.
> [...]
>
> Required Texture Formats
> [...]
> In addition, implementations are required to support the following sized
> internal formats.  Requesting one of these internal formats for any
> texture type will allocate exactly the internal component sizes and
> types shown for that format in tables 3.16-3.17:"
>
> Notably, however, GL_DEPTH_COMPONENT16 does /not/ appear in table 3.16
> or table 3.17.  It appears in table 3.18, where the "exact" rule doesn't
> apply, and thus we fall back to the "closely as possible" rule.
>
> The confusing part is that the ordering of the tables in the PDF is:
>
> Table 3.16 (pages 182-184)
> Table 3.18 (bottom of page 184 to top of 185)
> Table 3.17 (page 185)

ffs.

Yeah, let's just drop Z16 from the driver and the sized depth stuff from
the 3.0 piglit test.
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