linux-kernel - Re: [PATCH] perf/arm-cmn: fix compilation issue

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Message-ID: <ZGHt0OyK6ntqwqR6@FVFF77S0Q05N>
Date:   Mon, 15 May 2023 09:31:25 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     liming.wu@...uarmicro.com
Cc:     will@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, robin.murphy@....com
Subject: Re: [PATCH] perf/arm-cmn: fix compilation issue

On Mon, May 15, 2023 at 09:29:30AM +0800, liming.wu@...uarmicro.com wrote:
> From: Liming Wu <liming.wu@...uarmicro.com>
> 
> This patch is used to fix following compilation issue with legacy gcc
> and define variables at the beginning of the function
> 
> error: ‘for’ loop initial declarations are only allowed in C99 or C11 mode
> 2098 |                 for (int p = 0; p < CMN_MAX_PORTS; p++)

The kernel builds as gnu11 (i.e. C11 + GNU extensions) since commit:

  e8c07082a810fbb9 ("Kbuild: move to -std=gnu11")

... so that warning shouldn't be happenning.

How are you triggering this? Have you modified KBUILD_CFLAGS?

> Signed-off-by: Liming Wu <liming.wu@...uarmicro.com>
> ---
>  drivers/perf/arm-cmn.c | 13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/perf/arm-cmn.c b/drivers/perf/arm-cmn.c
> index 47d359f72957..2299fcde5b4a 100644
> --- a/drivers/perf/arm-cmn.c
> +++ b/drivers/perf/arm-cmn.c
> @@ -2009,8 +2009,11 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
>  	u16 child_count, child_poff;
>  	u32 xp_offset[CMN_MAX_XPS];
>  	u64 reg;
> -	int i, j;
> +	int i, j, p;
>  	size_t sz;
> +	void __iomem *xp_region;
> +	struct arm_cmn_node *xp;
> +	unsigned int xp_ports;
>  
>  	arm_cmn_init_node_info(cmn, rgn_offset, &cfg);
>  	if (cfg.type != CMN_TYPE_CFG)
> @@ -2067,9 +2070,9 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
>  	cmn->dns = dn;
>  	cmn->dtms = dtm;
>  	for (i = 0; i < cmn->num_xps; i++) {
> -		void __iomem *xp_region = cmn->base + xp_offset[i];
> -		struct arm_cmn_node *xp = dn++;
> -		unsigned int xp_ports = 0;
> +		xp_region = cmn->base + xp_offset[i];
> +		xp = dn++;
> +		xp_ports = 0;

None of these are for loop initial declarations. Even if we wanted to avoid the
warning, there's no need for these to change.

>  
>  		arm_cmn_init_node_info(cmn, xp_offset[i], xp);
>  		/*
> @@ -2095,7 +2098,7 @@ static int arm_cmn_discover(struct arm_cmn *cmn, unsigned int rgn_offset)
>  		 * from this, since in that case we will see at least one XP
>  		 * with port 2 connected, for the HN-D.
>  		 */
> -		for (int p = 0; p < CMN_MAX_PORTS; p++)
> +		for (p = 0; p < CMN_MAX_PORTS; p++)

This shouldn't be necessary given the jernel builds as gnu11.

Thanks,
Mark.

>  			if (arm_cmn_device_connect_info(cmn, xp, p))
>  				xp_ports |= BIT(p);
>  
> -- 
> 2.25.1
>