Re: [PATCH] firmware: smccc: default ARM_SMCCC_SOC_ID to disabled

[Satya Durga Srinivasu Prabhala]

Hello Neil,

On 1/14/2026 9:12 AM, Neil Armstrong wrote:
> On 1/13/26 07:24, Satya Durga Srinivasu Prabhala wrote:
> > The ARM SMCCC SoC ID driver is currently enabled by default and 
> > publishes
> > SMCCC-provided SoC identification into /sys/bus/soc/devices/socX/*.
> >
> > On platforms where a vendor SoC driver already exposes widely-consumed
> > attributes (e.g. Qualcomm socinfo [1]), enabling the SMCCC driver 
> > changes
> > the format of /sys/devices/soc0/soc_id (e.g. "jep106:XXYY:ZZZZ" instead
> > of a vendor logical ID like "519") and breaks existing userspace 
> > consumers.
> >
> > Flip the default of CONFIG_ARM_SMCCC_SOC_ID from y to n. Platforms that
> > prefer SMCCC over a vendor driver can explicitly enable it.
> >
> > This avoids unexpected format changes and keeps the generic SoC sysfs
> > stable on systems that rely on vendor-specific identification.
> >
> > [1]
> > Link: 
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/soc/qcom/socinfo.c
> >
> > Signed-off-by: Satya Durga Srinivasu Prabhala 
> > <satya.prabhala@xxxxxxxxxxxxxxxx>
> > ---
> >   drivers/firmware/smccc/Kconfig | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/firmware/smccc/Kconfig 
> > b/drivers/firmware/smccc/Kconfig
> > index 15e7466179a6..f830d11ebdca 100644
> > --- a/drivers/firmware/smccc/Kconfig
> > +++ b/drivers/firmware/smccc/Kconfig
> > @@ -18,8 +18,11 @@ config HAVE_ARM_SMCCC_DISCOVERY
> >   config ARM_SMCCC_SOC_ID
> >       bool "SoC bus device for the ARM SMCCC SOC_ID"
> >       depends on HAVE_ARM_SMCCC_DISCOVERY
> > -    default y
> > +    default n
> >       select SOC_BUS
> >       help
> >         Include support for the SoC bus on the ARM SMCCC firmware based
> >         platforms providing some sysfs information about the SoC 
> > variant.
> > +      Note: Several vendor platforms provide their own SoC information
> > +      drivers under drivers/soc/*. To avoid conflicting sysfs attribute
> > +      formats in /sys/devices/socX/*, this driver defaults to disabled.
> >
> > ---
> > base-commit: b71e635feefc852405b14620a7fc58c4c80c0f73
> > change-id: 20260112-disable_smccc_soc_id-ed09ef4d777f
> >
> > Best regards,
>
> Disabling it by default impacts other platforms, the arm64 kernel is 
> designed
> to be generic and run on any platform with defconfig and from the same 
> build,
> please don't forget that.

Thanks.

> If you want to ship an arm64 kernel tailored for Qualcomm platforms, 
> you're
> allowed, and you're also allowed to disable ARM_SMCCC_SOC_ID.

Not entirely true. Say in case of Android / GKI, ARM_SMCCC_SOC_ID gets 
enabled
by default and we do not have a way to disable it.

> The soc sysfs interface is designed to support multiple source of 
> information,
> from vendor (like qcom socinfo) and smccc ID. And this is well 
> documented,
> and pretty obvious...

Yes, it is indeed obvious. The point to note is vendor interface existed
from long time and unfortunately user space had made certain assumptions.
All, we need is a way for vendor to choose which interface to be provided
to user space to make sure user space isn't broken.

> Neil