On Tue, Mar 24, 2020 at 06:08:03PM +0100, Enric Balletbo i Serra wrote: > Hi Greg, > > On 24/3/20 17:49, Greg Kroah-Hartman wrote: > > On Tue, Mar 24, 2020 at 05:31:10PM +0100, Enric Balletbo i Serra wrote: > >> Hi Greg, > >> > >> Many thanks for your quick answer, some comments below. > >> > >> On 22/3/20 12:10, Greg Kroah-Hartman wrote: > >>> On Sun, Mar 22, 2020 at 10:43:34AM +0100, Enric Balletbo i Serra wrote: > >>>> This driver attaches to the ChromeOS ACPI device and then exports the values > >>>> reported by the ACPI in a sysfs directory. The ACPI values are presented in > >>>> the string form (numbers as decimal values) or binary blobs, and can be > >>>> accessed as the contents of the appropriate read only files in the sysfs > >>>> directory tree originating in /sys/devices/platform/chromeos_acpi. > >>>> > >>>> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@xxxxxxxxxxxxx> > >>> > >>> What is wrong with the "default" ACPI sysfs access? Why do you need a > >>> special driver just for this specific ACPI firmware? > >>> > >> > >> Please correct me if I am wrong, as I'm not an ACPI expert and I probably have > >> some ACPI leaks and misunderstandings. > >> > >> What is exporting this driver is the attributes for the non-default Chromebook > >> specific MLST ACPI method. Hence, I assumed we needed a special driver to expose > >> these values that can't be done using "default" ACPI sysfs. Note that these > >> attributes are dynamically created and are different between Chromebooks so need > >> some parsing. > >> > >> I didn't find a "standard" way to expose these attributes to userspace, so, > >> please kindly point me to one if there is one. > > > > Are you sure they aren't already there under /sys/firmware/acpi/? I > > thought all tables and methods were exported there with no need to do > > anything special. > > > > That's the first I did when I started to forward port this patch from chromeos > kernel to mainline. > > On my system I get: > > /sys/firmware/acpi/tables# > APIC DSDT FACP FACS HPET MCFG SSDT data dynamic > > (data and dynamic are empty directories) > > I quickly concluded (maybe wrong) that as there is no a MLST entry it was not > exported, but maybe one of those already contains the info? Or, should I expect > a MLST entry here? > > > What makes these attributes "special" from any other ACPI method? > > > > I can't answer this question right now. I need to investigate more I guess ;-) You can always ask the acpi developers as well, you need to get their review for your driver anyway :) good luck! greg k-h
