Re: [opensuse-arm] vcio, STRICT_DEVMEM

12 Mar 2019

      Matthias Brugger wrote:
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On 12/03/2019 09:04, Guillaume Gardet wrote:
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Hi Per,
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-----Original Message-----
From: Per Jessen 
Sent: 12 March 2019 08:58
To: opensuse-arm@opensuse.org
Subject: Re: [opensuse-arm] vcio, STRICT_DEVMEM
Per Jessen wrote:
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Matthias Brugger wrote:
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On 10/03/2019 19:35, Per Jessen wrote:
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Well, at least I have a vcio module that builds now, we'll see it
if it also works.
It seems that there is another thread on this mailing list, but I
wasn't able to find it. What do you want to achieve?
Hi Matthias,
nothing too complex I hope, I just want to control a series of
WS2812 LEDs, using the code/utilities from
https://github.com/jgarff/rpi_ws281x
I had a look on that code and it looks like a hack to me.
I can't really comment - of the couple of projects I looked at (related
to ws2812), this looked the most complete/useful.
...
...
...
I built the vcio module, seems to work fine.  Then I built the
kernel without STRICT_DEVMEM and I can now control a string of
WS2812 LEDs.
Thanks for your feedback!
The vcio module can probably be upstreamed, or at least packaged in
OBS, I guess.
I don't think this is the right approach for upstream. If we want to
control these leds, then we should write a kernel driver which uses
the mbox and not implement detection etc in user-space.
If you want to use a LED matrix, then I think this is a good candidate
for a tinydrm driver in the kernel.
again, I can't really comment on what is right or good - so just my
observations: 

getting the vcio module to work was no big deal, just required a bit of
research - I think even a relative newbie would manage to get it to
work.

About STRICT_DEVMEM - had I been able to disable with a kernel argument,
that would have been really nice.  In 2008, Bernhard Walle @ suse also
proposed a sysctl "dev.mem.restricted", but I guess that didn't go
through.  

-- 
Per Jessen, Zürich (5.0°C)
member, openSUSE Heroes.

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