Hello: I am attempting to get modedb to output a 15kHz Horizontal 320x240@60Hz signal. The standard VESA CEA mode 1,8 represents the digital implementation of SD resolution re: BT.601 https://en.wikipedia.org/wiki/Rec._601 Based on this information: https://www.kernel.org/doc/html/v5.4/fb/modedb.html It appears that modedb will pass my modeline set in the kernel to some CVT timing calculator and lets that derive the timings. I have found that this internal calculator doesn’t work, and using standard CVT timing selections produces incorrect results in the following manner: When selecting VESA Mode CEA 8, setting this mode in the kernel works perfectly, as evidenced by correctly displayed boot screen and initial pre-cmdline boot dialog. When cmdline parses and modedb sets the framebuffer, display goes blank. Modedb reports in /proc/cmdline video=HDMI-A-1:720x240M@60 but it does not output a usable signal. Since this signal is a standard VESA CEA mode, CVT should create the mode correctly, but there is clearly something wrong going on with the timings. Perhaps the CVT calculator is trying to produce a line-doubled or line-quadrupled mode with 31kHz horizontal? In any case, it’s not usable in the defined setup. Is this normal? Is there a workaround such as defining a custom video mode for the modedb pool with custom timings, etc? I found this old document: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/EDID/HOWTO.txt?id=be53bfdb8088e9d1924199cc1a96e113756b1075 Which mentions a method to insert a custom EDID, but I don't follow the method exactly. Is this something that could address the issue I am having? Thanks, Brian Goldberg
