Re: DRM Inquiry DPCD

[Jani Nikula]

On Wed, 23 May 2018, John Sledge  wrote:
> Do you have any suggestions or advice how to use the kernel driver in
> DRM in regards to how to implement the method drm_dp_dpcd_readb for
> example?

Sincerely, my suggestion is to respond and be active when people take
the time to look into your problem and reply to you [1].

BR,
Jani.


[1] 87fu2pxph0.fsf@intel.com">http://mid.mail-archive.com/87fu2pxph0.fsf@intel.com

-- 
Jani Nikula, Intel Open Source Graphics Center
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DRM Inquiry DPCD

[John Sledge]

Hi ,

I’ve been doing some PTN3460 programming under Linux and I have some questions 
regarding on setting the brightness level via DisplayPort Native Aux.
The display device with PTN3460 is connected in DP (display port) to my 
computer. I’m currently looking into the DRM (Direct Rendering Manager) a 
subsystem of the Linux kernel. It has a methods drm_dp_dpcd_readb, 
drm_dp_dpcd_read and drm_dp_dpcd_write. 
Do you have any suggestions or advice how to use the kernel driver in DRM in 
regards to how to implement the method drm_dp_dpcd_readb for example? I 
couldn't not find any test tool examples that implement it.


My goal is to create an application that would send/read bytes (brightness 
level) to address 0x722 or 0x723.


Namedrm_dp_dpcd_readb — read a single byte from the DPCDSynopsisssize_t 
drm_dp_dpcd_readb (    struct drm_dp_aux * aux,
               unsigned int offset,               u8 * valuep);
Argumentsaux - DisplayPort AUX channeloffset - address of the register to 
readvaluep - location where the value of the register will be 
storedDescriptionReturns the number of bytes transferred (1) on success, or a 
negative error code on failure.
Regards,John

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