* Suggestion for better HDMI console support
@ 2018-05-16 19:47 Thierry Moreau
0 siblings, 0 replies; only message in thread
From: Thierry Moreau @ 2018-05-16 19:47 UTC (permalink / raw)
To: linus-amlogic
Dear kernel developers,
I experimented with Odroid C2 Linux installation and I wanted an HDMI
display console. I succeeded but I needed a workaround which I report below.
My suggestion today is to implement the workaround logic inside the
kernel, which should be (technically at least) easy for some of you.
I noticed that the serial console is often suggested as a highly
recommended alternative for Amlogic SOC development. Maybe my suggestion
would change this (making the HDMI console working out of the box).
The problem I experienced with the Odroid C2 hdmi console display
output: for unknown reason, the kernel initializes the hdmi output in a
blank screen state that is exited only if the kernel receives two
requests: first to blank the (already blanked) screen and then to
unblank the screen. This sequence happens if a connected keyboard is
idle for 15 minutes and then touched by the user.
The workaround: I wrote a small C program that makes the two kernel
requests without wait.
Here is a snapshot:
#include <sys/ioctl.h>
#include <linux/vt.h>
#include <linux/tiocl.h>
static int blank_code=TIOCL_BLANKSCREEN;
static int unblank_code=TIOCL_UNBLANKSCREEN;
int main(int argc, char *argv[])
{
int td;
td=open("/dev/tty0",O_RDWR|O_NOCTTY);
if (td>=0) {
ioctl(td,TIOCLINUX,&blank_code);
ioctl(td,TIOCLINUX,&unblank_code);
}
}
My kernel version is 3.16.56 as customized to Odroid C2 by Hardkernel.
"Hope it helps!"
- Thierry Moreau
P.S. I am chasing installation hints for the Amlogic closed source
libraries for X.11 support in an otherwise plain vanilla Linux
innstallation (headless and server working fine). Any suggestion as
sources of info?
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