Re: [PATCH 2/3] drivers/perf: convert sysfs scnprintf family to sysfs_emit_at

[Joe Perches]

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...