Re: [PATCH 2/2] ACPI / osi: add DMI quirk for Dell systems

[Andy Shevchenko <andriy.shevchenko@linux.intel.com>]

On Mon, 2018-02-05 at 14:14 +0100, Jean Delvare wrote:

> On Wed, 31 Jan 2018 00:40:05 -0800, Alex Hung wrote:
> > A number of Dell systems require an OEM _OSI string "Linux-Dell-
> > Video" as
> > a BIOS workaround for a system hang bug caused by discrete VGA. The
> > form of
> > the OEM _OSI string is discussed in Documentation/acpi/osi.txt and
> > is
> > defined by each OEM.
> 
> I admit I don't understand how it is the operating system's job to
> carry the information from the BIOS to the BIOS.

> > +	for (i = 0; i < OSI_STRING_ENTRIES_MAX; i++) {
> > +		osi = &osi_setup_entries[i];
> > +		if (!strcmp(osi->string, str)) {
> 
> This can only happen if the user passes acpi_osi=Linux-Dell-Video or
> acpi_osi=!Linux-Dell-Video on the boot command line, right?
> 
> > +			osi->enable = true;
> 
> Does this not prevent the user from explicitly disabling it with
> acpi_osi=!Linux-Dell-Video ?

Playing with OSI string is a bad idea. I wouldn't do anything while
Rafael, or even Len can confirm that is the right thing to do.

For me, AFAIK we need to be bug-to-bug compatible with Windows (at least
on ACPICA side), so, what Windows exactly does on such laptops?

-- 
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy