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

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Date:   Thu, 1 Sep 2022 09:56:41 +0200
From:   Jens Wiklander <jens.wiklander@...aro.org>
To:     Sudeep Holla <sudeep.holla@....com>
Cc:     linux-kernel@...r.kernel.org, op-tee@...ts.trustedfirmware.org,
        Marc Bonnici <marc.bonnici@....com>,
        Achin Gupta <achin.gupta@....com>,
        Valentin Laurent <valentin.laurent@...stonic.com>,
        Lukas Hanel <lukas.hanel@...stonic.com>,
        Coboy Chen <coboy.chen@...iatek.com>
Subject: Re: [PATCH 4/9] firmware: arm_ffa: Add support for querying FF-A features

On Tue, Aug 30, 2022 at 12:07 PM Sudeep Holla <sudeep.holla@....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@....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.

Cheers,
Jens

> +
> +       return 0;
> +}
> +
>  static u32 ffa_api_version_get(void)
>  {
>         return drv_info->version;
> --
> 2.37.2
>