On Thursday 27 June 2019 14:13:22 David Wright wrote: > On Thu 27 Jun 2019 at 18:44:59 (+0300), Reco wrote: > > On Thu, Jun 27, 2019 at 10:24:51AM -0500, David Wright wrote: > > > That has led to finding these lines in systemd's journal: > > > > ... > > > > > Jun 27 09:47:06 west systemd-backlight[615]: [0;1;31mFailed to > > > write system 'brightness' attribute: Input/output error[0m > > > > ... > > > > > which suggests there's something wrong with the backlight. > > > > Hardly. More likely there's something wrong with the appropriate > > kernel facility. > > I'm afraid that's unlikely, based on the evidence that you snipped: > > On Fri 10 May 2019 at 13:20:39 -0500, David Wright wrote: > > > My interest in this stems from a Laptop on which you are blind > > > until the kernel loads (ie text pours down the screen). No > > > boot selection menu, no CMOS screens, no Grub screens. > > ↑↑↑↑↑↑↑↑↑↑↑↑↑↑↑ > > When the laptop is being powered up regularly, the display works for > about as long as the progress bar on the DELL screen takes to cross > from side to side: I would estimate it's about one second. The problem > came on gradually in Jan 2017. During use, the screen would flicker > a little, then die. > > So my strategy was (1) set the CMOS to boot USB/optical/hard drive in > that order. I did that a year ago, after it had been powered off for > a week. (2) Leave a stretch installation USB stick by it, ready for > whenever I got a chance to use it. (3) Go on holiday. When I got > back, I had a long enough period with a display showing to get to: > > ┌────────────────┤ [!!] Continue installation remotely using SSH > ├────────────────┐ │ > │ │ > Start SSH │ │ To continue the > installation, please use an SSH client to connect to the IP │ │ > address 192.168.1.xxx fe80::xxx:xxxx:xxxx:xxxx and log in as the > "installer" │ │ user. For example: > │ │ > │ │ ssh > instal...@192.168.1.xxx > │ │ > │ │ The fingerprint of this SSH server's host key is: > │ │ > │ │ > SHA256:xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx > │ │ > │ │ Please check this carefully against the > fingerprint reported by your SSH client.│ │ > │ │ > <Continue> │ │ > > │ > └───────────────────────────────────────────────────────────────────── >────────────┘ > > at which point I'm home and dry. > > > Basically what this systemd unit tries to do is to write a saved > > value to /sys/class/backlight/intel_backlight/brightness. > > Kernel responds to this with EIO, which is unusual for the laptop > > (to be expected for the desktop as there's no backlight there). > > > > It may be possible to workaround this with certain knobs of i915 > > kernel module (enable_dpcd_backlight or invert_brightness), I'd try > > the latter first. > > I.e. try adding "i915.invert_brightness=1" or > > "i915.enable_dpcd_backlight=1" to the kernel's commandline. > > Yes, I've also looked at the values from /sys/…/*backlight/… and they > all behave sensibly. But the screen flickers a little, then goes out. > That's why I think it might be something like a capacitor charging up. > Over a period of weeks, it could discharge back to behaving normally. > > But I'm not looking for a fix to the problem, just workarounds to make > it possible to do things like install, that require the early screens > which the external monitor won't display. > > Cheers, > David.
That sounds an awful lot like the filter caps have failed. If handy with a small screwdriver, open that lappy and check all the aluminum cans for bulging where the scratches are across the tops. And if possible since the psu bricks are well sealed, try a fresh psu. If the cans have bulged tops, that's a sure sign the electrical characteristic called ESR has gone above and ohm or so. Unless you are handy with a workstation type soldering kit, its probably less trouble to just replace the lappy with a new one. There was a period a decade back where the capacitors were legendarily bad. Your unit may have some of them in it. Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis Genes Web page <http://geneslinuxbox.net:6309/gene>
