Hello Hans, thanks for reaching out. On Tue, May 14, 2019 at 1:23 AM Hans de Goede <hdegoede@xxxxxxxxxx> wrote: > > Hi João, All, > > I've been helping a Fedora user debugging a problem where the backlight turns off and > never turns on again with newer kernels: > https://bugzilla.redhat.com/show_bug.cgi?id=1697069 > > At this point I'm pretty sure this commit is the culprit: > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=78f3ac76d9e5 > > The breakage happens between 4.20.4 and 4.20.5 and that commit is the only one > standing out; and blacklisting eeepc-wmi fixes things. > > For now I'm going to add a new DMI quirk for this (patch for this will follow later) > but this is something to keep in mind if we get more reports about backlight/display > breakage on eeepc laptops. I'm thinking that maybe the new behavior introduced > by commit 78f3ac76d9e5 should only be applied to laptops using > asus-nb-wmi and not to laptop using eeepc-wmi (the code modified > by the commit is common to both drivers). > Actually there was another report from a user via private email with similar symptoms on a Asus Eee PC 1015BX -- no backlight after starting the kernel (probably after eeepc-wmi is probed) -- which I've been meaning to reply for a couple of weeks now, so I'm also cc'ing others involved in that thread. In that case the user was able to work around the problem by passing acpi_backlight=vendor, just to add an extra datapoint. > João, can you check if the 11 models mentioned in the commit msg > (or a bunch of similar models you have access too) are using asus-nb-wmi; > or eeepc-wmi ? > All of the 11 models where we saw this problem are using asus_nb_wmi: E203NAS, GL553VE, X441NC, X441UVK, X541UVK, X555DG, X555UB, X555UQ, X560UD, X570ZD, X705FD. Furthermore, from the 144 Asus models we have in our database at Endless, only 10 probe the eeepc_wmi module: D320SF-K, D415MT, D520MT, D640SA, D830MT, G11DF, V221ID, V272UN, ZN220IC-K, ZN241IC. 6 out of these 10 also probe asus_nb_wmi: D640SA, G11DF, V221ID, V272UN, ZN220IC-K, ZN241IC. And the 4 that only probe eeepc_wmi are all desktop models: D320SF-K, D415MT, D520MT, D830MT. I agree with limiting this behavior to asus-nb-wmi only on mainline -- it will still apply to the original affected hardware, and it is much better than keep updating a list of DMI quirks. We will also need to send it to a few linux-stable branches as well. Best regards, ...................................................................................... João Paulo Rechi Vita | Endless
