linux-kernel - Re: [PATCH 2/5] firmware: arm_scmi: imx: Add i.MX95 CPU Protocol

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Message-ID: <ac1a1ebe-ef97-42a2-a2be-529a656a7706@stanley.mountain>
Date: Wed, 22 Jan 2025 15:41:41 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Cristian Marussi <cristian.marussi@....com>
Cc: "Peng Fan (OSS)" <peng.fan@....nxp.com>,
	Sudeep Holla <sudeep.holla@....com>,
	Shawn Guo <shawnguo@...nel.org>,
	Sascha Hauer <s.hauer@...gutronix.de>,
	Pengutronix Kernel Team <kernel@...gutronix.de>,
	Fabio Estevam <festevam@...il.com>, linux-kernel@...r.kernel.org,
	arm-scmi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	imx@...ts.linux.dev, Peng Fan <peng.fan@....com>
Subject: Re: [PATCH 2/5] firmware: arm_scmi: imx: Add i.MX95 CPU Protocol

On Wed, Jan 22, 2025 at 12:22:18PM +0000, Cristian Marussi wrote:
> > > +struct scmi_msg_imx_cpu_attributes_out {
> > > +	__le32 attributes;
> > > +#define	CPU_MAX_NAME	16
> > > +	u8 name[CPU_MAX_NAME];
> > 
> > char is always unsigned in the kernel these days but strings should
> > still always be char.  Same thing in patch 1, there were a couple u8
> > names.
> > 
> 
> While it is certainly true that char is the way to go for strings and, as
> such, it is used elsewhere to hold the resource names across all SCMI
> protocols, in this context it is a field of structure representing
> exactly the layout of message reply coming from the server, and defined
> in the SCMI spec as a uint8 array, so, we have generally preferred to
> used u8 to represent such fixed size array all across the SCMI stack
> protocols implementation....
> 
> .... not saying that it is necessarily completelt right, but that is the
> reason we are guilty :D

Fine.  I don't have intense emotions about this.

It does slightly bother me when we assume that the SCMI server NUL
terminates these when we do things like:

	dev_info(ph->dev, "i.MX CPU: name: %s\n", out->name);

But from a practical perspective we have to trust the SCMI server.

regards,
dan carpenter