access "Display Port Helper Functions" trough userspace

[Jani Nikula]

On Sat, 18 Apr 2015, Marc Ludwig <Brotbuechsenleasing at gmx.de> wrote:
> Hi, Folks!
>  
> I'am looking for an opportunity to access the I2C-Interface which is attached
> to my displayport link.
> Can anyone give me a hint aubout an minimal working example for this?
>  
> I tried to figure aut how this could be solved using the linux userspace, but
> for me it looks like i have to implement my own driver
> according to https://www.kernel.org/doc/htmldocs/drm/ch02s05.html#idp10812112
>  this should be done by describing an
> drm_dp_aux_msg structure, which is passed into a driver's .transfer
>  implementation.

You may be conflating two things here. DP has a native AUX channel, and
I2C-over-AUX on top. If it's DDC you're after, you want I2C, and the I2C
adapters are exposed to userspace. You might want to have a look at
ddccontrol [1]. It's not minimal and seems to be abandoned, but last
time I tried I could use it to control my monitor.

If it's DP AUX you're after (why?) there was some discussion about
adding such an interface in the thread starting at [2].

BR,
Jani.


[1] http://ddccontrol.sourceforge.net/
[2] http://mid.gmane.org/1428493301-20293-1-git-send-email-durgadoss.r@intel.com


> Furthermore i was looking into some packages (the working machine runs an
> ArchLinux-Distro) which where provided.
> $ extra/libdrm 2.4.60-2 :Userspace interface to kernel DRM services
> $ extra/libva-intel-driver 1.5.1-1 : VA-API implementation for Intel G45 and HD
> Graphics family (the working machine has an Intel HD4000 GPU)
> But none of them does provide such helper functions.
>  
> Thank you for your time, with kind Regards,
>  
>  
> Marc
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-- 
Jani Nikula, Intel Open Source Technology Center