Re: [PATCH 4/9] firmware: arm_ffa: Add support for querying FF-A features

[Sudeep Holla <sudeep.holla@arm.com>]

On Thu, Sep 01, 2022 at 09:56:41AM +0200, Jens Wiklander wrote:
> On Tue, Aug 30, 2022 at 12:07 PM Sudeep Holla <sudeep.holla@arm.com> wrote:
> >
> > Add support for FFA_FEATURES to discover properties supported at the
> > FF-A interface. This interface can be used to query:
> >  - If an FF-A interface is implemented by the component at the higher EL,
> >  - If an implemented FF-A interface also implements any optional features
> >    described in its interface definition, and
> >  - Any implementation details exported by an implemented FF-A interface
> >    as described in its interface definition.
> >
> > Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
> > ---
> >  drivers/firmware/arm_ffa/driver.c | 23 +++++++++++++++++++++++
> >  1 file changed, 23 insertions(+)
> >
> > diff --git a/drivers/firmware/arm_ffa/driver.c b/drivers/firmware/arm_ffa/driver.c
> > index 04e7cbb1b9aa..de94073f4109 100644
> > --- a/drivers/firmware/arm_ffa/driver.c
> > +++ b/drivers/firmware/arm_ffa/driver.c
> > @@ -571,6 +571,29 @@ static int ffa_memory_reclaim(u64 g_handle, u32 flags)
> >         return 0;
> >  }
> >
> > +static int ffa_features(u32 func_feat_id, u32 input_props, u32 *if_props)
> > +{
> > +       ffa_value_t id;
> > +
> > +       if (!ARM_SMCCC_IS_FAST_CALL(func_feat_id) && input_props) {
> > +               pr_err("%s: Invalid Parameters: %x, %x", __func__,
> > +                      func_feat_id, input_props);
> > +               return ffa_to_linux_errno(FFA_RET_INVALID_PARAMETERS);
> > +       }
> > +
> > +       invoke_ffa_fn((ffa_value_t){
> > +               .a0 = FFA_FEATURES, .a1 = func_feat_id, .a2 = input_props,
> > +               }, &id);
> > +
> > +       if (id.a0 == FFA_ERROR)
> > +               return ffa_to_linux_errno((int)id.a2);
> > +
> > +       if (if_props)
> > +               *if_props = id.a2;
>
> w3 (id.a3) also contains a value when querying for
> FFA_MEM_RETRIEVE_REQ. I see that in "[PATCH 5/9] firmware: arm_ffa:
> Use FFA_FEATURES to detect if native versions are supported" you're
> using this function with if_props = NULL. So I guess that at the
> moment we have more than needed, but in case you need to add another
> parameter to this function you'll need to update all the call sites
> too.
>

Right, I clearly missed to observe that. I am fine either way. Do you
have any preference ? As long as the callers are with this driver, it
shouldn't be much of an issue to change all, but happy to update to
accommodate w3 as well in v2.

--
Regards,
Sudeep