Re: [PATCH 1/4] powerpc/rtas: Handle special return format for RTAS_FN_IBM_OPEN_ERRINJCT

[Sourabh Jain <sourabhjain@linux.ibm.com>]

On 05/12/25 15:15, Narayana Murty N wrote:
> RTAS_FN_IBM_OPEN_ERRINJCT returns results in special format:
>    rets[0] = session token (output)
>    rets[1] = status code
>    rets[2..] = additional outputs (if any)
>
> Unlike standard RTAS calls where:
>    rets[0] = status code
>    rets[1..] = outputs
>
> This patch adds special handling for OPEN_ERRINJCT to:
> 1. Check correct status position (rets[1]) for __fetch_rtas_last_error()
> 2. Copy all rets[0..nret-1] to outputs[] (including token at rets[0])
> 3. Return status from rets[1] instead of rets[0]
>
> Reference: OpenPOWER PAPR documentation
> 	   https://files.openpower.foundation/s/XFgfMaqLMD5Bcm8
> Signed-off-by: Narayana Murty N <nnmlinux@linux.ibm.com>
> ---
>   arch/powerpc/kernel/rtas.c | 30 ++++++++++++++++++++++++------
>   1 file changed, 24 insertions(+), 6 deletions(-)
>
> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
> index 8d81c1e7a8db..04c8438aadda 100644
> --- a/arch/powerpc/kernel/rtas.c
> +++ b/arch/powerpc/kernel/rtas.c
> @@ -1183,7 +1183,7 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
>   	unsigned long flags;
>   	struct rtas_args *args;
>   	char *buff_copy = NULL;
> -	int ret;
> +	int ret = 0;
>   
>   	if (!rtas.entry || token == RTAS_UNKNOWN_SERVICE)
>   		return -1;
> @@ -1213,15 +1213,33 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
>   	va_rtas_call_unlocked(args, token, nargs, nret, list);
>   	va_end(list);
>   
> +	/* Special handling for RTAS_FN_IBM_OPEN_ERRINJCT for error fetching */

It would be more helpful if we explain why special handling is needed.


>   	/* A -1 return code indicates that the last command couldn't
>   	   be completed due to a hardware error. */
> -	if (be32_to_cpu(args->rets[0]) == -1)
> +

The above empty line can be avoided.

> +	if (token == rtas_function_token(RTAS_FN_IBM_OPEN_ERRINJCT) && nret > 1)
> +		ret = be32_to_cpu(args->rets[1]);
> +	else if (nret > 0)
> +		ret = be32_to_cpu(args->rets[0]);
> +
> +	if (ret == -1)It would be more helpful if we explain why special handling is needed.
>
>   		buff_copy = __fetch_rtas_last_error(NULL);
>   
> -	if (nret > 1 && outputs != NULL)
> -		for (i = 0; i < nret-1; ++i)
> -			outputs[i] = be32_to_cpu(args->rets[i + 1]);
> -	ret = (nret > 0) ? be32_to_cpu(args->rets[0]) : 0;
> +	/* Handle outputs and return status */

Return status is already handled above, isn't it?

> +	if (nret > 1 && outputs != NULL) {
> +		if (token == rtas_function_token(RTAS_FN_IBM_OPEN_ERRINJCT)) {
> +			/* Special case: rets[0]=token, rets[1]=status, rets[2..]=outputs */
> +			for (i = 0; i < nret; ++i)
> +				outputs[i] = be32_to_cpu(args->rets[i]);
> +		} else {
> +			/* Normal case: rets[0]=status, rets[1..]=outputs */
> +			for (i = 0; i < nret - 1; ++i)
> +				outputs[i] = be32_to_cpu(args->rets[i + 1]);
> +		}
> +	} else {
> +		/* No outputs: just ret is status */
> +		ret = (nret > 0) ? be32_to_cpu(args->rets[0]) : 0;
> +	}

Do we really need to calculated the ret again here?

>   
>   	lockdep_unpin_lock(&rtas_lock, cookie);
>   	raw_spin_unlock_irqrestore(&rtas_lock, flags);

- Sourabh Jain