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

From: liuqi (BA)
Date: Thu Mar 18 2021 - 05:34:56 EST

On 2021/3/17 22:57, Joe Perches wrote:
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",

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);


Hi Joe,

I'll fix the use of sysfs_emit_at in next version, thanks.
But I think it's better to keep the res as ssize_t, as the return value of this function is ssize_t.



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