Re: [OE-core] [PATCH v2] mesa: Add native patch via a variable

Mark Hatle
2022-10-28T18:02:47Z

On 10/28/22 5:59 AM, Alexander Kanavin wrote:
> Thanks. What I would want to understand is whether this arrangement
> should have its own
> MACHINE_FEATURE, e.g. 'vendor-egl' or similar, and then mesa proper
> would be configured accordingly to
> disable bits that come from the vendor.
>
> Is there a particular need for a separate recipe?

When libmali support is enabled in our configuration we do the following:

define a mali400 MACHINEOVERRIDE

Then we use PREFERRED_PROVIDER to switch:

https://github.com/Xilinx/meta-xilinx/blob/master/meta-xilinx-core/conf/machine/include/machine-xilinx-default.inc#L25

virtual/libgles1
virtual/libgles2
virtual/egl
virtual/libgl
virtual/mesa

So the mesa-gl

the PROVIDES are:

virtual/libgl virtual/mesa

while in mesa:

PROVIDES = " \
${@bb.utils.contains('PACKAGECONFIG', 'opengl', 'virtual/libgl', '', d)} \
${@bb.utils.contains('PACKAGECONFIG', 'gles', 'virtual/libgles1
virtual/libgles2 virtual/libgles3', '', d)} \
${@bb.utils.contains('PACKAGECONFIG', 'egl', 'virtual/egl', '', d)} \
${@bb.utils.contains('PACKAGECONFIG', 'gbm', 'virtual/libgbm', '', d)} \
virtual/mesa \
"

While it might be possible to switch around the PROVIDES using distibution
configuration or similar, this has been difficult to get right in the past.
This is why the split happened, it's one or the other based on the configuration.

--Mark

> Alex
>
> On Thu, 27 Oct 2022 at 02:46, Mark Hatle <mark.hatle@kernel.crashing.org> wrote:
>>
>>
>>
>> On 10/26/22 1:01 PM, Alexander Kanavin wrote:
>>> Is there a combination of libmali recipe and mesa-gl somewhere public
>>> so we could try to pick it apart and see what links to where?
>>
>> libmali is ALWAYS implementation specific. You will need to pick a vendor and
>> build for it. What is generic is the application interface (from what I've been
>> told.). I can give you the AMD (Xilinx) instructions. But you likely won't be
>> able to actually execute the code without a corresponding board. (AFAIK QEMU
>> doesn't have any mali400 emulation.)
>>
>> And to be clear, libmali provides the interfaces, but it is NOT a replacement to
>> mesa, it works WITH mesa, just the 'gl' part (not the gles part).
>>
>> The following is an abbreviated attempt to show how the pieces interact with
>> each other. It may not be 100% correct, I am definitely not an expert at this.
>> (For example, I don't understand why it's "DRM" in some places but "DRI" in
>> others. These seem to be 'generally' the same systems.) But it's how the parts
>> and pieces appear to be put together based on a functioning system.
>>
>>
>> In a 'normal' system (mesa):
>>
>> mesa provides:
>> libglapi.so.0
>> libEGL.so.1
>> libGLESv2.so.2
>> (and others)
>>
>> The CONFIG_DRM_LIMA backend and whatever the display port DRM (CONFIG_DRM_XLNX)
>> go through a dlopened backend module, which USUALLY talks to a kernel module for
>> any hardware access through a standard (known) kernel interface.
>>
>> In our case the dynamic modules would be the lima_dri.so and xlnx_dri.so.
>>
>> glmark2-es2-wayland ->
>> libwayland-client
>> libwayland-cursor
>> libwayland-egl.so.1
>>
>> I believe the libwayland-egl talks to weston "somehow" for the egl interfaces,
>> via the libwayland-client? but I'm fuzzy here.
>>
>> Weston has two related items:
>>
>> drm-backend.o ->
>> libglapi.so.0 (dlopened)
>>
>> This bit uses mesa to access the DRM backend to actually display the stuff..
>>
>> gl-backend.so ->
>> libwayland-server
>> libEGL.so.1
>> libGLESv2.so.2
>>
>> This backend is used to render the items.
>>
>>
>> So the glmark2 does it's benchmarking and renders (gl-backend) through Weston
>> backends to the display port (drm-backend).
>>
>> In the above case it all comes from mesa, the drm and libELG/libGLESv2 parts.
>>
>>
>>
>> The following shows a libmali configured system as a contrasts to the above:
>>
>> libmali-xlnx provides:
>>
>> libEGL.so.1
>> libGLESv1_CM.so.1
>> libGLESv2.so.2
>> libmali.so.9
>> libgbm.so.1
>>
>> (also provides specific backends for fbdev, headless, wayland and x11)
>>
>>
>> It talks to a backend kernel module called 'mali.ko'
>>
>> mesa provides:
>>
>> libGL.so.1
>> libglapi.so.0
>>
>> and also swrast dri interface
>>
>> glmark2-es2-wayland ->
>> libwayland-client
>> libwayland-cursor
>> libwayland-egl.so.1
>>
>> (same as above)
>>
>> drm-backend.o ->
>> libwayland-server
>> libdrm.so.2
>> libMali.so.9
>>
>> gl-backend.so ->
>> libwayland-server
>> libMali.so.9
>>
>> So in the above, libMali is providing all of the APIs of libEGL and libGLESv2,
>> as well as (enough of) libglapi for the built in raster implementation.
>>
>>
>> Compiling things like Chromium that will link directly, you move from linking to
>> libGL.so from mesa to linking in libMali, along with libGL from mesa. The
>> libMali will provide the core set of APIs, while the libGL will augement them
>> with additional APIs.
>>
>> Cairo is another utility that similar modifies in this way.
>>
>>
>> To re-iterate, it's NOT a "swap libmali" and re-use everything. You need to
>> rebuild anything that links to libgles or libgl or even libglapi with this new
>> configuration. It's API compatible, NOT ABI compatible!
>>
>>
>> I hope this helps. As far as letting you play with it, I'm working through the
>> final stuff and should have something I can push to langdale/master on the
>> meta-xilinx and meta-xilinx-tools soon.
>>
>> --Mark
>>
>>> My (perhaps confused) understanding is similar to Joshua's: 'gl' is
>>> basically 'opengl in x11' or 'opengl rendered to memory', and if a
>>> system uses neither, then it is not needed.
>>>
>>> Alex
>>>
>>> On Wed, 26 Oct 2022 at 19:48, Joshua Watt <jpewhacker@gmail.com> wrote:
>>>>
>>>> On Wed, Oct 26, 2022 at 12:21 PM Mark Hatle
>>>> <mark.hatle@kernel.crashing.org> wrote:
>>>>>
>>>>>
>>>>>
>>>>> On 10/26/22 11:03 AM, Alexander Kanavin wrote:
>>>>>> On Wed, 26 Oct 2022 at 16:35, Mark Hatle <mark.hatle@kernel.crashing.org> wrote:
>>>>>>> (I just saw this, so a little late on the reply, but..)
>>>>>>>
>>>>>>> mesa-gl is ABSOLUTELY still being used. It's needed for libmali usage. Not
>>>>>>> everyone wants to use lima support for graphics.
>>>>>>>
>>>>>>> It was broken into two separate packages so that is was VERY clear if you were
>>>>>>> using mesa for 'everything' (mesa), or mesa JUST for 'gl' (not gles).
>>>>>>
>>>>>> Okay, I'm not going to propose this, but can you clarify, what is the
>>>>>> current use for 'gl'? Is it just opengl 3d in standalone x server
>>>>>> based systems (which is slowly dying), or is there something else to
>>>>>> it?
>>>>
>>>> Are you specifically talking about libmali with the following statements?
>>>>
>>>> I would say that in general libmali is probably not doing things in
>>>> the "normal" way if so, although I'm not trying to say that it isn't a
>>>> legitimate way to do it.
>>>>
>>>>>
>>>>> Anything that needs "OpenGL", i.e. Wayland/Weston, X11, Chromium, etc etc etc.
>>>>> These all end up linking to a combination of libmali and mesa-gl.
>>>>
>>>> In general (maybe not for libmali) Wayland and Weston themselves don't
>>>> use OpenGL, or mesa-gl. Individual clients may be able to use it,
>>>> although it's rare in my (incomplete) experience. Most of the OpenGL
>>>> users in Wayland/Weston are going through XWayland/X11 and using GLX.
>>>>
>>>>>
>>>>> Pretty much anything that depends on 'virtual/gl' (vs virtual/libgles1,2,3).
>>>>> libmali provides virtual/libgles1 and virtual/libgles2 and a few other things
>>>>> that meta-gl doesn't.
>>>>>
>>>>> libmali also doesn't include the DRM/DRI parts. This comes from mesa-gl.
>>>>
>>>> In general, DRM/DRI doesn't come from mesa-gl. libdrm is its own
>>>> recipe, and libgbm comes from mesa proper, or from some other
>>>> dedicated vendor specific libgbm recipe.
>>>>
>>>>
>>>> If this is sidetracking the discussion please ignore; I'm just a
>>>> little confused by the above statements because either A) libmali is
>>>> really weird B) my understanding of things is _way_ off, or C) the
>>>> statements aren't quite correct.
>>>>
>>>>>
>>>>> --Mark
>>>>>
>>>>>> Alex
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>
>>
>>
>>
>>
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