Re: [PATCH v2] perf/arm_pmu_platform: Fix an error message related to dev_err_probe() usage

[Robin Murphy]

On 2022-08-05 21:55, Christophe JAILLET wrote:
> dev_err() is a macro that expand dev_fmt, but dev_err_probe() is a
> function and cannot perform this macro expansion.
>
> So hard code the "hw perfevents: " prefix and dd a comment explaining why.
>
> Fixes: 11fa1dc8020a ("perf/arm_pmu_platform: Use dev_err_probe() for IRQ errors")
> Signed-off-by: Christophe JAILLET <christophe.jaillet@xxxxxxxxxx>
> ---
> Untested, but I can't see how it could work.
>
> v1 --> v2
>    - fix a typo in the comment
> ---
>   drivers/perf/arm_pmu_platform.c | 7 +++++--
>   1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/perf/arm_pmu_platform.c b/drivers/perf/arm_pmu_platform.c
> index 513de1f54e2d..02cca4b8f0fd 100644
> --- a/drivers/perf/arm_pmu_platform.c
> +++ b/drivers/perf/arm_pmu_platform.c
> @@ -101,8 +101,11 @@ static int pmu_parse_irqs(struct arm_pmu *pmu)
>   	struct device *dev = &pdev->dev;
>   
>   	num_irqs = platform_irq_count(pdev);
> -	if (num_irqs < 0)
> -		return dev_err_probe(dev, num_irqs, "unable to count PMU IRQs\n");
> +	if (num_irqs < 0) {
> +		/* dev_err_probe() does not handle dev_fmt, so hard-code the prefix */
> +		return dev_err_probe(dev, num_irqs,
> +				     "hw perfevents: unable to count PMU IRQs\n");

Why not use dev_fmt directly? But even better, is there any practical 
reason why this couldn't be fixed at the source by indirecting 
dev_err_probe() through a macro wrapper just like all its friends:

#define dev_err_probe(dev, err, fmt, ...) \
	_dev_err_probe(dev, err, dev_fmt(fmt), ##__VA_ARGS__)

?

Thanks,
Robin.

> +	}
>   
>   	/*
>   	 * In this case we have no idea which CPUs are covered by the PMU.