Re: [PATCH v3] i2c: i801: Safely share SMBus with BIOS/ACPI

[Alex Henrie <alexh@vpitech.com>]

On Sat, 18 Dec 2021 12:39:11 +0900
Hector Martin <marcan@marcan.st> wrote:

> On 18/12/2021 11.51, Alex Henrie wrote:
> > On Fri, 17 Dec 2021 16:41:05 +0900
> > Hector Martin <marcan@marcan.st> wrote:
> > 
> >> On 17/12/2021 09.31, Alex Henrie wrote:
> >>> I am having a similar problem, but unfortunately this patch doesn't
> >>> work for me (I get the error "BIOS uses SMBus unsafely"). Would it be
> >>> acceptable to add a module parameter to allow access to the SMBus, even
> >>> if the BIOS is using it? I realize that this is not a good idea in
> >>> general, but I believe it is safe in my particular case, and I don't
> >>> see any other way to solve my problem.
> >>
> >> How is this safe in your case? If the BIOS is using SMBus without
> >> locking it, and may do so at any time, then there's no way to safely use
> >> it from Linux.
> > 
> > The BIOS appears to access the SMBus during the first few minutes after
> > boot, and then it stops using it. So "safe" may not be the right word,
> > but in my case, it seems to work OK to use the SMBus as long as the
> > uptime is greater than a few minutes.
> 
> Linux will probe the SMBus on startup, so that still seems like a rather
> fragile situation. You'd have to blacklist the module and load it
> separately a few minutes after boot, or something like that...

It's awful, I agree. I was just hoping to find a slightly less awful
solution than patching the kernel to remove the BIOS access check,
which is what I currently have to do. It seems to me that if multiple
people are in this situation, it might make sense to add a module
parameter to disable the check.

-Alex