Re: [PATCH v2 0/1] platform/x86: asus-wmi: add support for ASUS screenpad

[Luke Jones <luke@ljones.dev>]

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**snip**
> >> Question 2:
> >> 
> >> If you turn the second screen off through drm/kms, using the desktop
> >> environments monitor config panel does this also turn off the
> >> backlight ?
> > 
> > The screen is dark but there is still some backlight coming out of it.
> > I think this means I need to add a small pre-off to the patch to ensure
> > backlight is fully off when display is turned off.
> 
> I'm afraid that this is not going to be easy to fix at the kernel level,
> we first need to tie backlight control to drm-connectors as I proposed
> (and plan to implement when I can make time):
> 
> https://lore.kernel.org/dri-devel/b61d3eeb-6213-afac-2e70-7b9791c86d2e@redha
> t.com/
> 
> Once that is in place we can simply make the drm-code call out to
> the backlight driver and have it turn the backlight off when disabling
> the output through the drm/kms interface.

Okay cool. But until then I can set the screenpad to turn brightness off when 
it does the call to:
err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_POWER, 0, NULL);
here I can also do before that call:
err = asus_wmi_set_devstate(ASUS_WMI_DEVID_SCREENPAD_LIGHT,ctrl_param, NULL);

Then when the patch you mention is done this can be removed.

**snip** 
> > I would like to go with the backlight patch as it seems more likely I
> > can adjust this without breaking userspace if required in future. The
> > WMI controls behave as expected to.
> 
> Ok, lets go with the v2 which adds /sys/class/backlight support then.
> 
> I must warn you though if this does turn out to cause issues I'll have
> no choice but to revert it.
> 
> I must admit I've lost track a bit of the state of v2 during this
> discussion.  Can I pick up v2 as is, or were there (other) remarks
> which need addressing and should I expect a v3 ?

There will be a V3. I don't anticipate any issues at all with this, and some 
folks have been using this patch with Gnome and KDE since V2 was submitted.

> 
> ####### Switch to (off-topic) GPU mux discussion ########
**snip**
> >> I think the best thing to do here is to just use EFI on machines like
> >> this. That or put grub in text mode so that it makes BIOS calls to
> >> display text. Using GRUB_TERMINAL_OUTPUT=gfxterm combined with
> >> classic BIOS booting will make grub try to directly drive the gfx
> >> card itself and I'm not surprised that it gets that wrong in this
> >> case.
> >> Note I think that just using EFI is prefered over switching grub to
> >> GRUB_TERMINAL_OUTPUT=console. I would expect
> >> GRUB_TERMINAL_OUTPUT=console to also work but I'm not sure. I don't
> >> think that the classic BIOS boot stuff is still tested by laptop
> >> vendors and esp. not tested with non standard BIOS settings ...
> > 
> > The grub gfx mode is GRUB_TERMINAL_OUTPUT="console", fedora default in
> > all cases here. Grub itself shows fine when the MUX mode is in dgpu
> > mode (aka, internal display connected to dgpu).
> 
> Ah ok, so I misunderstood and the problem only happens *after* grub?
> 
> Have I understood that correctly?
> 
> And this is on Fedora with the nvidia binary driver ?
> 
> The problem then likely is that the nvidia binary driver is not in
> the initrd (which is by design since it may need to be rebuild on
> a driver update while the kernel is kept at the same version,
> so the initrd won't be rebuild).

That was indeed the issue. It also creates new problems for when a user wants 
to use iGPU only via the plain (and frankly not adequate or good) method of 
simply removing the dGPU from the device tree.

Currently I maintain the supergfxd tool which is a lot more advanced than the 
other gpu switchers around, and I expose both the above method, and also PCI 
hotplug, and the ASUS WMI method (which I now think is used by other vendors 
also). Hotplug and Asus method can force the device off, and it can't be 
brought back by a PCI rescan - but to do so safely the Nvidia drivers must be 
unused and unloaded. I guess I'll need to tweak the boot process of supergfxd 
and block things until this is done.

Maybe we can move this to a new topic, because there looks to be a few things 
to discuss in relation to hybrid laptops, and specifically Nvidia with MUX, 
and Advanced Optimus.

Cheers,
Luke.



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