Messages in this thread | | | Subject | Re: [Linuxarm] Re: [PATCH 2/3] drivers/perf: convert sysfs scnprintf family to sysfs_emit_at | From | Joe Perches <> | Date | Thu, 18 Mar 2021 06:33:25 -0700 |
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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");
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