Re: [PATCH v3 01/24] firmware: arm_scmi: Add new SCMIv4.0 error codes definitions

[Cristian Marussi <cristian.marussi@arm.com>]

On Fri, Jun 12, 2026 at 03:10:59AM -0700, Usama Arif wrote:
> On Sun, 29 Mar 2026 17:33:12 +0100 Cristian Marussi <cristian.marussi@arm.com> wrote:
> 

Hi Usama,

Thanks for having a look at this first of all !

I was busy posting a V4 before merge window last week so this late
reply....

I am already planning a V5 in -rc1 in two weeks where beside some more
minor ABI additions I will plan to address any incoming reviews and
some residual minor issues I know about (mostly sparse related)

...but you are CCed already in V4...

> > SCMIv4.0 introduces a couple of new possible protocol error codes: add
> > the needed definitions and mappings to Linux error values.
> > 
> > Signed-off-by: Cristian Marussi <cristian.marussi@arm.com>
> > ---
> >  drivers/firmware/arm_scmi/common.h | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/firmware/arm_scmi/common.h b/drivers/firmware/arm_scmi/common.h
> > index 7c35c95fddba..44af2018e21d 100644
> > --- a/drivers/firmware/arm_scmi/common.h
> > +++ b/drivers/firmware/arm_scmi/common.h
> > @@ -45,6 +45,8 @@ enum scmi_error_codes {
> >  	SCMI_ERR_GENERIC = -8,	/* Generic Error */
> >  	SCMI_ERR_HARDWARE = -9,	/* Hardware Error */
> >  	SCMI_ERR_PROTOCOL = -10,/* Protocol Error */
> > +	SCMI_ERR_IN_USE = -11,  /* In Use Error */
> > +	SCMI_ERR_PARTIAL = -12, /* Partial Error */
> >  };
> >  
> >  static const int scmi_linux_errmap[] = {
> > @@ -60,6 +62,8 @@ static const int scmi_linux_errmap[] = {
> >  	-EIO,			/* SCMI_ERR_GENERIC */
> >  	-EREMOTEIO,		/* SCMI_ERR_HARDWARE */
> >  	-EPROTO,		/* SCMI_ERR_PROTOCOL */
> > +	-EPERM,			/* SCMI_ERR_IN_USE */
> 
> "In use" reads like a resource-state failure, where -EBUSY would normally be expected.
> -EPERM suggests an authorization failure,  which is already represented by SCMI_ERR_ACCESS.
> 

The usage of this in Telemetry is indeed a resource state failure that relates to groups usage
and it means something like "this is busy now, so you cannot do that now with this current config"
...but you are definitely right that -EPERM does NOT fit well here and especially is NOT what IN_USE
should signify in general in SCMI as a return code for future users.

I will fix in V5.

Thanks,
Cristian