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

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Message-ID: <a2ccfc0f-5790-ef03-d357-ab606f40b3c5@huawei.com>
Date:   Thu, 18 Mar 2021 17:33:50 +0800
From:   "liuqi (BA)" <liuqi115@...wei.com>
To:     Joe Perches <joe@...ches.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: [Linuxarm] Re: [PATCH 2/3] drivers/perf: convert sysfs scnprintf
 family to sysfs_emit_at



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.

Thanks,

Qi

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