linux-kernel - Re: [PATCH 2/3] drivers/perf: convert sysfs scnprintf family to sysfs_emit

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Message-ID: <eae7016a8cd8f426987dd5c4a2a56c4ec6d28a6e.camel@perches.com>
Date:   Wed, 17 Mar 2021 07:57:59 -0700
From:   Joe Perches <joe@...ches.com>
To:     Qi Liu <liuqi115@...wei.com>, john.garry@...wei.com,
        zhangshaokun@...ilicon.com, will@...nel.org, mark.rutland@....com
Cc:     linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linuxarm@...neuler.org
Subject: Re: [PATCH 2/3] drivers/perf: convert sysfs scnprintf family to
 sysfs_emit_at

On Wed, 2021-03-17 at 17:41 +0800, Qi Liu wrote:
> Use the generic sysfs_emit_at() function take place of scnprintf()
[]
> diff --git a/drivers/perf/arm-ccn.c b/drivers/perf/arm-ccn.c
[]
> @@ -328,41 +328,37 @@ static ssize_t arm_ccn_pmu_event_show(struct device *dev,
>  			struct arm_ccn_pmu_event, attr);
>  	ssize_t res;
>  
> 
> -	res = scnprintf(buf, PAGE_SIZE, "type=0x%x", event->type);
> +	res = sysfs_emit(buf, "type=0x%x", event->type);
>  	if (event->event)
> -		res += scnprintf(buf + res, PAGE_SIZE - res, ",event=0x%x",
> +		res += sysfs_emit_at(buf + res, res, ",event=0x%x",
>  				event->event);

sysfs_emit_at should always use buf, not buf + offset.
res should be int and is the offset from buf for the output

so the form should be similar to

	int len;

	len = sysfs_emit(buf, "type=0x%x", event->type);
	if (event->event) {
		len += sysfs_emit_at(buf, len, ",event=0x%x", event->event);

		etc...