Hello,
Cc-ing Peter Zijlstra
lkml.kernel.org/r/728a8e68-ea4b-4040-a0fc-217df4f19...@redhat.com
lkml.kernel.org/r/20180817081947.m425gok2ugt7t...@pathway.suse.cz
lkml.kernel.org/r/00c60dca-60bc-8568-eaa3-d4b0c326c...@redhat.com
On (08/17/18 06:36), Prarit Bhargava wrote:
> On 08/17/2018 05:38 AM, Sergey Senozhatsky wrote:
> > On (08/16/18 13:39), Prarit Bhargava wrote:
> >>
> >> + auto [X86] Enable ACPI SPCR console
> > ^^^^
> > And arm64?
>
> Hi Sergey, on arm64 if an SPCR is present the early console and console are
> initialized by default. IOW no kernel parameter is necessary to initialize
> the
> console in that case.
OK, thanks.
> > Any chance we can rename param to "spcr" or something more clear?
> > To explicitly state what exactly it's going to do. `auto' sounds
> > too general and doesn't tell me that much. I'm probably the only
> > here who can't see a connection between "auto" and "SPCR", but
> > still.
>
> I came up with "auto" because I think it is generic. I also thought about
> "console=fw", or just "console". If in the future another arch wants to
> optionally bring up a firmware or hardware defined console then they could use
> auto too.
Hmm, I see your point.
My [sort of a] problem with "auto" is that it tells me as much as "magic"
[and "magic" tells me almost nothing]. By the way, would be fun if we had
"magic" instead of "auto" all over the kernel
echo "magic" > /sys/bus/usb/...../power/control
> > void arch_console_setup(void)
> > {
> > if (acpi_parse_spcr(false, true))
> > pr_err(.........);
> > }
> >
> > There can be other consoles in the system, logging an error is not
> > such a useless thing.
>
> I can make the second change. The problem (IIRC) with returning an error in
> an
> setup fn is that the rest of the setup functions will not execute. I don't
> want
> to fail the setup callbacks because of an incorrect SPCR table.
OK, fair enough.
Letting users know that SPCR is incorrect also makes sense, so option #2
I guess is what we want after all.
> Like I mentioned to Petr, I'd like to know if you (or anyone else) has strong
> feelings about changing the behaviour of earlycon on x86? I could make it so
> that specifying just earlycon would also initialize the console.
x86 people and/or scheduler people might have strong opinions on this.
I Cc-ed Peter Zijlstra; he represents both groups and is known to be
a hardcore earlycon user.
-ss
