linux-kernel - Re: [PATCH] firmware: smccc: default ARM_SMCCC_SOC

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Message-ID: <aWgEn4GmKwUOjNPe@bogus>
Date: Wed, 14 Jan 2026 21:03:27 +0000
From: Sudeep Holla <sudeep.holla@....com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: Satya Durga Srinivasu Prabhala <satya.prabhala@....qualcomm.com>,
	Mark Rutland <mark.rutland@....com>,
	Sudeep Holla <sudeep.holla@....com>,
	Lorenzo Pieralisi <lpieralisi@...nel.org>,
	linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org, trilok.soni@....qualcomm.com
Subject: Re: [PATCH] firmware: smccc: default ARM_SMCCC_SOC_ID to disabled

On Wed, Jan 14, 2026 at 09:37:24PM +0200, Dmitry Baryshkov wrote:
> On Wed, Jan 14, 2026 at 10:04:21AM -0800, Satya Durga Srinivasu Prabhala wrote:
> > Hello Dmitry,
> > 
> > On 1/13/2026 3:25 AM, Dmitry Baryshkov wrote:
> > > On Mon, Jan 12, 2026 at 10:24:06PM -0800, 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.
> > > NAK, the userspace should not depend on the exact kernel configuration.
> > > Consider working with distribution kernels, which would enable this
> > > driver anyway.
> > As I mentioned in the other replies, vendor interface exists before the
> > standard
> > interface and user space heavily relies on soc0 already. If not disabling
> > the
> > SMCCC SOC ID by default. I believe, we should  at-least have a way to make
> > sure vendors can disable SMCCC SOC ID by some means or have vendor
> > interface takes precedence.
> 
> Please correct me if I'm wrong, what do you observe? SMCCC device on
> soc0 and qcom_socinfo at soc1?
> 
> In such a case the ABI file, Documentation/ABI/testing/sysfs-devices-soc clearly
> defines that there might be several different SoC devices (identified by
> different drivers, etc). If the userspace depends on qcom_socinfo device
> being soc0, then the userspace is broken.
> 
> Last, but not least, the soc_id format is documented in the ABI
> document. It is clearly allowed to have jep106 format in the soc_id. So,
> I think, you have two options: disable SMCCC 1.2+ in the firmware or
> adapt the userspace. You can't control e.g. the kernel that will be
> running on your platform (it very well can be a standard distro kernel
> from Debian, Ubuntu or Fedora, which obviously will have that driver
> enabled).
> 

Completely agree to all the points made here.

-- 
Regards,
Sudeep