Re: [PATCH] char: nvram: disable on ARM

On 07/02/2018 at 16:47:00 +0100, Alexandre Belloni wrote:

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I really don't think anyone is using that but I don't really know much
about x86 and the specification this may be part of.

I see the info may be used in drivers/video/fbdev/ and
drivers/platform/x86/thinkpad_acpi.c

The thinkpad_acpi driver seems to look at some other bytes
in the nvram, which have a platform specific meaning.

Yeah, I was more concerned that they need drivers/char/nvram.c for
nvram_read_byte so we can't simply remove the driver.

Ok, so the procfs interface may be obsolete, but we still need an
interface into the CMOS NVRAM data.

Actually, I just found
https://unix.stackexchange.com/questions/331419/is-dev-nvram-dangerous-to-write-to

So it seems to have real values for some people (even if they are
wrong).

That also points to https://sourceforge.net/projects/nvram-wakeup/ but I
don't think it is necessary. The RTC driver should be able to wakeup an
x86 platform.

All the other uses of /dev/nvram I could find with a simple google
search (i.e. saving and restoring CMOS settings) could just use
/sys/class/rtc/rtc0/device/nvram

Ok, the chromeos guys are using it for verified boot it seems:
https://chromium.googlesource.com/chromiumos/platform/vboot_reference

I'm wondering whether they really care about the checksum though.

-- 
Alexandre Belloni, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
http://bootlin.com