On Thu, 2021-03-18 at 17:33 +0800, liuqi (BA) wrote:
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", 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...
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.
The 2nd arg of sysfs_emit_at is int. On 64 bit platforms, ssize_t is 64 bit while int is 32. If res (or len) is ssize_t, there could be a lot of -Wconversion warnings like this produced when using make W= warning: conversion from ‘ssize_t’ {aka ‘long int’} to ‘int’ may change value [-Wconversion] 262 | len += sysfs_emit_at(buf, len, "\n");