linux-kernel - Re: [PATCH] firmware: arm_scmi: fix SMCCC_RET_NOT

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Date:   Thu, 14 May 2020 15:29:24 +0100
From:   Sudeep Holla <sudeep.holla@....com>
To:     Etienne Carriere <etienne.carriere@...aro.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH] firmware: arm_scmi: fix SMCCC_RET_NOT_SUPPORTED
 management

On Thu, May 14, 2020 at 10:24:28AM +0200, Etienne Carriere wrote:
> Fix management of argument a0 output value of arm_smccc_1_1_invoke() that
> should consider only SMCCC_RET_NOT_SUPPORTED as reporting an unsupported
> function ID as correctly stated in the inline comment.
>

I agree on the comment part, but ...

> Signed-off-by: Etienne Carriere <etienne.carriere@...aro.org>
> ---
>  drivers/firmware/arm_scmi/smc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/arm_scmi/smc.c b/drivers/firmware/arm_scmi/smc.c
> index 49bc4b0e8428..637ad439545f 100644
> --- a/drivers/firmware/arm_scmi/smc.c
> +++ b/drivers/firmware/arm_scmi/smc.c
> @@ -115,7 +115,7 @@ static int smc_send_message(struct scmi_chan_info *cinfo,
>  	mutex_unlock(&scmi_info->shmem_lock);
>  
>  	/* Only SMCCC_RET_NOT_SUPPORTED is valid error code */
> -	if (res.a0)
> +	if (res.a0 == SMCCC_RET_NOT_SUPPORTED)
>  		return -EOPNOTSUPP;

Now this will return 0 for all values other than SMCCC_RET_NOT_SUPPORTED.
Is that what we need ? Or do you see non-zero res.a0 for a success case ?
If later, we need some fixing, otherwise it is safer to leave it as is
IMO.

-- 
Regards,
Sudeep