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Sender: Chris Gagneraud <chgans@googlemail.com>
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Date: Sun, 28 Jul 2013 03:18:05 +1200
From: Christian Gagneraud <chgans@gna.org>
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To: "Sundareson, Prabindh" <prabu@ti.com>
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Cc: "meta-ti@yoctoproject.org" <meta-ti@yoctoproject.org>
Subject: Re: [Qt5] mkspecs/devices: beagleboard == am335x ?
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On 07/27/2013 02:20 PM, Sundareson, Prabindh wrote:
> The device approach is useful for adding platform specific hooks for
> eglfs via EGLFS_PLATFORM_HOOKS_SOURCES, so it is a good thing. So it is
> more of a convenience/cleaner way, than anything related to performance.
>

I do agree with Dennys about the compiler flags, yocto knows what are 
the best flags for the machine/device.
What is nice with the device file approach is the specification for 
OpenGL includes, libs, QPA and the EGLFS hooks as well.
Basically I like the fact that all the OpenGL "mess" is sorted out in 
one place (when it comes to compilation).
Interesting examples are the Rasberry Pi [1] and Freescale i.mx6 [2].

when considering Qt alone (out of Yocto/OE), I think as a SoC vendor, it 
is the best way to make sure your users get the best of Qt5/OpenGL, and 
very easily according to [3] (not tested).


When it comes to Yocto, I didn't see any easy way for meta-bsp to tell 
meta-qt5 how to configure/build qt5 w/ OpenGL support.
It seems to me that the only way is through the .bbappend, in qtbase.inc:
[...]
# if you want to enable egl/gles2 in your .bbappend, don't forget to add 
right dependencies, e.g.
# GL_DEPENDS = "virtual/libgles2 virtual/egl"
# QT_GLFLAGS = "-opengl es2 -eglfs"
GL_DEPENDS ?= "virtual/libgl"
QT_GLFLAGS ?= "-opengl"
[...]

Could/should this be used by the meta-ti layer?

I spent some time recently going through meta-qt5 recently (as well as 
the qt4 stuff), I even tried an alternative configure/method, so far 
unsuccessfully. My feeling is that meta-qt5 tries to adapt qt5 to OE, I 
think it should be done the other way around, that's my very personal view.

I really would like to see a Yocto Qt5 SDK one of these days.

Prabindh, could you tell more about the status of Qt5/OpenGL for TI 
SoCs, what about this commit [4]? Is it possible to build within Yocto 
Qt5 w/ OpenGL support for AM335x platforms?

Regards,
Chris

[1] 
http://qt.gitorious.org/qt/qtbase/trees/stable/mkspecs/devices/linux-rasp-pi-g++
[2] 
http://qt.gitorious.org/qt/qtbase/trees/stable/mkspecs/devices/linux-imx6-g++
[3] 
http://blog.qt.digia.com/blog/2012/04/13/cross-compiling-qt-for-the-masses/
[4] 
https://github.com/prabindh/meta-qt5/commit/c8129fb5057f9254c773f82d2fdbd85d9c56410a


>
> regards
> Prabindh
> ________________________________________
> From: meta-ti-bounces@yoctoproject.org [meta-ti-bounces@yoctoproject.org] on behalf of Dmytriyenko, Denys
> Sent: Saturday, July 27, 2013 2:36 AM
> To: Christian Gagneraud
> Cc: meta-ti@yoctoproject.org
> Subject: Re: [meta-ti] [Qt5] mkspecs/devices: beagleboard == am335x ?
>
> On Fri, Jul 26, 2013 at 10:45:02AM +1200, Christian Gagneraud wrote:
>> Hi there,
>>
>> In qtbase sources, there are a couple of "device" definitions files,
>> according to [1], this greatly help cross-compiling qt5.
>> This device file specify things for CPU and GPU optimisations. So
>> basically these files are tightly coupled with BSP providers.
>>
>> One of them is linux-beagleboard-g++ [2], is it appropriate to use
>> this one for AM335x based platform as well?
>>
>> The meta-qt5 layer doesn't seem to use this feature, but if it did,
>> would this device config files help to get an optimised Qt5 build
>> for TI SoCs? Especially, would that help to get OpenGL stuff sorted
>> out?
>>
>> Regards,
>> Chris
>>
>> [1] http://blog.qt.digia.com/blog/2012/04/13/cross-compiling-qt-for-the-masses/
>> [2] https://qt.gitorious.org/qt/qtbase/trees/stable/mkspecs/devices/linux-beagleboard-g++
>
> Chris,
>
> Looking at those files shows very basic compiler optimization flags being set,
> -march, -mtune, -mfpu etc. I don't see any GL or GPU specifics in there. It
> also hardcodes things like soft-fp, which is not good. All this stuff is
> alredy taken care of by the build framework and I'm sure meta-qt5, like the
> old qt4, sets all the right COMPILER_FLAGS to get the most performance from
> the target CPU.
>
> --
> Denys
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