DingoAus
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Impact of New Linux Kernel

Tue Jan 26, 2016 1:38 am

I was reading this article about changes the next version of the Linux kernel (http://www.phoronix.com/scan.php?page=a ... ures&num=1) and read the following:

"While the VC4 DRM driver was previously added as the Raspberry Pi kernel mode-setting driver, the kernels up to now haven't had the necessary bits for supporting 3D/OpenGL in conjunction with the new VC4 Gallium3D driver from Mesa. However, with Linux 4.5 those needed kernel bits are in place for having a fully open Raspberry Pi 3D driver stack."

Does anyone have more information about what this means?

jdb
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Re: Impact of New Linux Kernel

Tue Jan 26, 2016 11:55 am

In practice for regular users of Raspbian, not much. The default VCHIQ-based driver is still enabled by default and will be for a while yet until any regressions are found and bug-fixed.

We're likely to include it in a future release of Raspbian but disabled-by-default.

Having KMS, Gallium and DRM support on Pi means that OpenGL can be supported (instead of OpenGLES) and full Kernel Modesetting (automatic display detection and configuration from within Linux). It would also in theory allow for deactivation of a large portion of the VPU blob (about 1/3rd of start.elf).
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DingoAus
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Re: Impact of New Linux Kernel

Tue Jan 26, 2016 12:09 pm

Wow, would that mean OpenGL could be supported in hardware?

That would likely have a huge impact on what I plan to do with graphics.

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kusti8
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Re: Impact of New Linux Kernel

Tue Jan 26, 2016 12:12 pm

DingoAus wrote:Wow, would that mean OpenGL could be supported in hardware?

That would likely have a huge impact on what I plan to do with graphics.
Once the work is done, yes. But that won't be done by 4.5, there's still a ways to go. You can try it out and see how it works for you.
There are 10 types of people: those who understand binary and those who don't.

ShiftPlusOne
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Re: Impact of New Linux Kernel

Tue Jan 26, 2016 12:14 pm

Yes, but don't expect miracles. And actually, you might see it well before 4.5 in raspbian ;).

mimi123
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Re: Impact of New Linux Kernel

Tue Jan 26, 2016 5:54 pm

DingoAus wrote:Wow, would that mean OpenGL could be supported in hardware?

That would likely have a huge impact on what I plan to do with graphics.
The RPi is DirectX 10(9Ex profile) and OpenGL 2.1 capable with current drivers, it may even get better in the future :)

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bstrobl
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Re: Impact of New Linux Kernel

Sat Jan 30, 2016 7:08 pm

jdb wrote: It would also in theory allow for deactivation of a large portion of the VPU blob (about 1/3rd of start.elf).
What are the other two thirds used for? I assume all the decode logic along with the rtos takes a decent chunk.

Also, is an open source blob without the hardware decoders possible? I believe it was mentioned once that an open source blob might be made available but am guessing due to patents that a bunch of chip features would be deactivated/unavailable.

jdb
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Re: Impact of New Linux Kernel

Sat Jan 30, 2016 7:18 pm

bstrobl wrote:What are the other two thirds used for? I assume all the decode logic along with the rtos takes a decent chunk.

Also, is an open source blob without the hardware decoders possible? I believe it was mentioned once that an open source blob might be made available but am guessing due to patents that a bunch of chip features would be deactivated/unavailable.
RTOS, Audio handling (HD audio codecs such as DTS, Dolby), h.264 encode/decode, VC1/MPEG2 decode, CSI camera, DSI displays, power and clock management (which is now about 75% working under upstream Linux).

And yes, most of the stuff in the blob is covered under patent - either from companies licencing the codec(s) or because the interfaces are Broadcom proprietary. A FOSS blob would probably have none of these features available.
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bstrobl
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Re: Impact of New Linux Kernel

Sat Jan 30, 2016 8:12 pm

jdb wrote: And yes, most of the stuff in the blob is covered under patent - either from companies licencing the codec(s) or because the interfaces are Broadcom proprietary. A FOSS blob would probably have none of these features available.
Thanks for the info. I take it that because of a loss of all those features an open source blob is pretty low on the priority list, since it would probably only appeal to those who are concerned with running proprietary code.

jdb
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Re: Impact of New Linux Kernel

Sat Jan 30, 2016 8:36 pm

bstrobl wrote:
Thanks for the info. I take it that because of a loss of all those features an open source blob is pretty low on the priority list, since it would probably only appeal to those who are concerned with running proprietary code.
Correct.

It would make absolutely no sense to remove such a large set of features which incidentally are the main selling points of the Pi, publish it as "open-source software" and promote it to those that are interested, then blame Richard Stallman for the reduction in product quality.

The more of the SoC that's in the public domain is more of a learning opportunity for people that want to know what's going on inside their little green board, but expanding this is a case of perpetually chipping away at the pervasive belief that proprietary systems maximise profits.

Don't take my word for it; here's GabeN in 2013:
https://www.youtube.com/watch?v=rCGMiT0CQAI
Rockets are loud.
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