linux-kernel - Re: [PATCH] firmware: arm_scmi: fix voltage description in failure cases

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Message-ID: <ZqO9s9YzYjaCHSap@bogus>
Date: Fri, 26 Jul 2024 16:16:03 +0100
From: Sudeep Holla <sudeep.holla@....com>
To: Etienne Carriere <etienne.carriere@...s.st.com>
Cc: <linux-kernel@...r.kernel.org>,
	Cristian Marussi <cristian.marussi@....com>,
	<arm-scmi@...r.kernel.org>, <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] firmware: arm_scmi: fix voltage description in failure
 cases

On Thu, Jul 25, 2024 at 08:53:17AM +0200, Etienne Carriere wrote:
> Reset the reception buffer max size when a voltage domain description
> request fails, for example when the voltage domain returns an access
> permission error (SCMI_ERR_ACCESS) unless what only a single 32bit
> word is read back for the remaining voltage description requests
> responses leading to invalid information. The side effect of this
> issue is that the voltage regulators registered from those remaining
> SCMI voltage domain were assigned a wrong regulator name.
> 
> Signed-off-by: Etienne Carriere <etienne.carriere@...s.st.com>
> ---
>  drivers/firmware/arm_scmi/voltage.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/firmware/arm_scmi/voltage.c b/drivers/firmware/arm_scmi/voltage.c
> index 2175ffd6cef5..f1a7c04ae820 100644
> --- a/drivers/firmware/arm_scmi/voltage.c
> +++ b/drivers/firmware/arm_scmi/voltage.c
> @@ -229,8 +229,10 @@ static int scmi_voltage_descriptors_get(const struct scmi_protocol_handle *ph,
>  		/* Retrieve domain attributes at first ... */
>  		put_unaligned_le32(dom, td->tx.buf);
>  		/* Skip domain on comms error */
> -		if (ph->xops->do_xfer(ph, td))
> +		if (ph->xops->do_xfer(ph, td)) {
> +			ph->xops->reset_rx_to_maxsz(ph, td);

I am fine with this to keep it simple, but thought I will check my thoughts.
We usually use reset_rx_to_maxsz in iterators as we don't know the expected
size of the response, whereas here it must be max sizeof(*resp_dom).

That said, we don't have any helpers and changing xfer->rx.len directly
doesn't looks good ? Or may be it is OK ? Thoughts ?

--
Regards,
Sudeep