https://bgstack15.ddns.net/blog/enContents © 2022 <a href="mailto:bgstack15@gmail.com">bgstack15</a> <a rel="license" href="https://creativecommons.org/licenses/by-sa/4.0/"> <img alt="Creative Commons License BY-SA" style="border-width:0; margin-bottom:12px;" src="https://bgstack15.ddns.net/.images/l_by-sa_4.0_88x31.png"></a>Wed, 12 Oct 2022 13:00:32 GMTNikola (getnikola.com)http://blogs.law.harvard.edu/tech/rsshttps://bgstack15.ddns.net/blog/posts/2022/10/12/ddcontrol-for-monitors/bgstack15<h2>The story</h2> <p>I use an Nvidia graphics card on my Devuan Ceres desktop. I also use two monitors, and a kvm switch for one of the monitors. On the other monitor I have a 3-input HDMI input switcher. Some article I read on the Internet suggested that one can use software to interact with the monitors, using the ddc protocol. I think DDC is how my old computers could recognize what was plugged in to my VGA port (and nowadays, VGA, displayport, and unfortunately some HDMI) by name.</p> <p>On GNU/Linux, that software is ddccontrol. To enable Nvidia to pass through ddc protocol, I had to enable a module parameter. I set value in new file <code>/etc/modprobe.d/nvidia-registry.conf</code> which turns on the i2c capabilities of my <code>01:00.0 VGA compatible controller: NVIDIA Corporation GP107 [GeForce GTX 1050 Ti] (rev a1)</code>.</p> <div class="code"><pre class="code literal-block"><span class="n">options</span><span class="w"> </span><span class="n">nvidia</span><span class="w"> </span><span class="n">NVreg_RegistryDwords</span><span class="o">=</span><span class="s">"RMUseSwI2c=1"</span><span class="w"></span> </pre></div> <p>I re-ran update-initramfs to ensure even the initram has this new setting.</p> <div class="code"><pre class="code literal-block">sudo update-initramfs -u -k $( uname -r ) </pre></div> <p>After a reboot (just to be sure), in userspace, I can now query the monitor. To learn the input field:</p> <div class="code"><pre class="code literal-block">$ ddccontrol dev:/dev/i2c-4 -d <span class="p">|</span> grep -i input Control 0x60: +/5/3 C <span class="o">[</span>Input Source Select <span class="o">(</span>Main<span class="o">)]</span> </pre></div> <p>My two identical Samsung monitors ended up needing slightly different ddccontrol commands. I suspect this is due to one is connected via HDMI and one via DP.</p> <p>My <code>monitor-left-hdmi.sh</code> command:</p> <div class="code"><pre class="code literal-block">ddccontrol dev:/dev/i2c-4 -r 0x60 -w '5' </pre></div> <p><code>monitor-left-dp.sh</code>:</p> <div class="code"><pre class="code literal-block">ddccontrol dev:/dev/i2c-4 -r 0x60 -w '3' </pre></div> <p><code>monitor-right-vga.sh</code>:</p> <div class="code"><pre class="code literal-block">ddccontrol dev:/dev/i2c-2 -r 0x60 -w '1' ddccontrol dev:/dev/i2c-2 -r 0xdb -w '4' ddccontrol dev:/dev/i2c-2 -r 0xdc -w '6' ddccontrol dev:/dev/i2c-2 -r 0xeb -w '253' </pre></div> <p><code>monitor-right-hdmi.sh</code>:</p> <div class="code"><pre class="code literal-block">ddccontrol dev:/dev/i2c-2 -r 0xdb -w '253' ddccontrol dev:/dev/i2c-2 -r 0xdc -w '260' ddccontrol dev:/dev/i2c-2 -r 0xeb -w '9' ddccontrol dev:/dev/i2c-2 -r 0x60 -w '5' </pre></div> <p>I learned all those by evaluating the output of <code>ddccontrol dev:/dev/i2c-4 -d</code> after manually choosing the inputs I cared about.</p> <p>These monitors didn't have prebuilt profiles in the ddccontrol-db.</p>ddccontroldisplaydrivergraphicsmonitorsshellhttps://bgstack15.ddns.net/blog/posts/2022/10/12/ddcontrol-for-monitors/Wed, 12 Oct 2022 12:58:53 GMT