On 27 May 2015 at 19:05, Ken Moffat <[email protected]> wrote: > On Wed, May 27, 2015 at 10:57:32AM -0500, Bruce Dubbs wrote: > > Richard Melville wrote: > > >I've just configured my latest kernel (4.0.3) to utilise KMS (thanks > Ken) > > >rather than the legacy vesafb, but of course this has created other > > >problems. > > > > > >The upside is that the font size on the console looks good on my monitor > > >(1440x900) and the backlight now switches itself off when required -- it > > >must have been broken on vesafb. > > > > > >The downside is that the EDID information fed to the kernel appears to > give > > >the wrong screen size. Only about 60% of the width and height are used. > > > > > >Maybe there's something I've missed in the kernel config. I've now > turned > > >off all legacy frame buffer settings that I can find, but it's made no > > >difference. > > > > > >My feeling is that the monitor EDID info is corrupt; it's a cheap and > > >fairly old model of unknown origin. If this is the case then I need to > > >build an EDID file and place it in /lib/firmware. But first I have to > > >discover exactly what the setting are for my monitor. > > > > > >My questions are: has anybody successfully built a custom EDID file, and > > >what is the best way to query the monitor for the settings? Normally I > > >would use xrandr, but I don't have xorg (with its libraries) installed, > and > > >I don't need it. Can xrandr be installed standalone? I've found a > couple > > >of other tools on the web (read-edid and edid-rw) but I'm unfamiliar > with > > >them. > > > > > >Any help much appreciated, otherwise I'll plough on alone :-( > > > > I've never had to do anything like that, but my first step would be to > try a > > commercial distro and see if the same problem persists. I'd also take a > > look at the Xorg log. > > > > -- Bruce > > > Those sound like good places to start - remember to backup grub.cfg > so you can restore it after the distro is installed. >
I'm using syslinux rather than grub. I'll boot a live Mint version from a USB flash drive which should (maybe) give some indication of the problem. > > There seem to be *two* EDID config options which mention FIRMWARE in > the kernel, but I'm not sure which I use (my server uses one, but > not sure about my desktops), and if it really is corrupt then I > doubt changing the config will help. > Linus says it should http://is.gd/gUjI2t > > There is a read-edid or parse-edid tool (lots of references if you > google 'linux EDID'), but it seems to be used to get the right data > from a working example of the same monitor. I did find a post which > mentioned setting custom modelines : I guess using xrandr would be > the least painful way to try that (and ctrl-alt-backspace if it goes > bad : hope it doesn't trash the monitor). > I don't have Xorg installed; I'm only using the Intel I915 frame buffer. I'll try xrandr from the live Mint boot. > > I also found an oldish post mentioning setting up a conf file for > the monitor with options including > > Option "UseEDID" "FALSE" > and also Horizsync and Vertrefresh ranges > > but I'm not sure if it worked. > Thanks Ken, I'll plod on. Richard
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