Re: [PATCH 07/13] scpi: ignore init_versions failure if reported not supported

[Sudeep Holla]

On 23/08/16 15:55, Neil Armstrong wrote:
> On 08/23/2016 04:54 PM, Sudeep Holla wrote:
> > On 23/08/16 09:23, Neil Armstrong wrote:
> > > On 08/19/2016 06:46 PM, Sudeep Holla wrote:
> > > > On 18/08/16 11:11, Neil Armstrong wrote:
> > > > > In Amlogic GXBB Legacy SCPI, the LEGACY_SCPI_CMD_SCPI_CAPABILITIES report
> > > > > as SCPI_ERR_SUPPORT, so do not fail if this command is not supported.
> > > > >
> > > > > Signed-off-by: Neil Armstrong <narmstrong@xxxxxxxxxxxx>
> > > > > ---
> > > > >  drivers/firmware/arm_scpi.c | 12 +++++++-----
> > > > >  1 file changed, 7 insertions(+), 5 deletions(-)
> > > > >
> > > > > diff --git a/drivers/firmware/arm_scpi.c b/drivers/firmware/arm_scpi.c
> > > > > index 3fe39fe..d3be4c5 100644
> > > > > --- a/drivers/firmware/arm_scpi.c
> > > > > +++ b/drivers/firmware/arm_scpi.c
> > > > > @@ -1111,12 +1111,13 @@ err:
> > > > >          ret = scpi_info->ops->init_versions(scpi_info);
> > > > >      else
> > > > >      ret = scpi_init_versions(scpi_info);
> > > > > -    if (ret) {
> > > > > +    if (ret && ret != -EOPNOTSUPP) {
> > > > >          dev_err(dev, "incorrect or no SCP firmware found\n");
> > > > >          scpi_remove(pdev);
> > > > >          return ret;
> > > > >      }
> > > >
> > > > Why not deal it in init_versions itself.
> > > >
> > > > > +    if (ret != -EOPNOTSUPP) {
> > > > >      _dev_info(dev, "SCP Protocol %d.%d Firmware %d.%d.%d version\n",
> > > > >            PROTOCOL_REV_MAJOR(scpi_info->protocol_version),
> > > > >            PROTOCOL_REV_MINOR(scpi_info->protocol_version),
> > > >
> > > > Why not have default value like 0.0 ? Just add a comment. Since get
> > > > version is exported out, IMO having default value makes more sense. What
> > > > do you think ?
> > > >
> > > > > @@ -1124,15 +1125,16 @@ err:
> > > > >            FW_REV_MINOR(scpi_info->firmware_version),
> > > > >            FW_REV_PATCH(scpi_info->firmware_version));
> > > > >
> > > > > +        ret = sysfs_create_groups(&dev->kobj, versions_groups);
> > > > > +        if (ret)
> > > > > +            dev_err(dev, "unable to create sysfs version group\n");
> > > > > +    }
> > > > > +
> > > >
> > > > Again this can stay as is if we have default.
> > >
> > > Printing version 0.0 firmware 0.0.0 is a nonsense for me...
> >
> > OK 0.0 was a wrong example. May be 0.1 ?
> >
> > Since the driver has already exposed, hypothetically user-space can use
> > that information, so IMO, we need to expose some static version for pre-v1.0
> >
> > I am surprised that capability is not supported as this was present even
> > in that legacy SCPI. Do you know what happens if you send that command ?
> > Have you done some experiments on that ?
>
> I've experimented and returns EOPNOTSUPP, Amlogic confirmed to us the command was not implemented.
>
> This a clearly a corner-case.

OK, thanks for the confirmation.
Not exporting anything could be kind of breaking ABI as it was not made
optional when introduced :( (you can blame me ;))

--
Regards,
Sudeep