linux-kernel - Re: [PATCH v3 1/4] HID: hid-picolcd*: Convert sprintf/scnprintf to sysfs_emit/sysfs_emit

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Date: Tue, 19 Mar 2024 01:21:20 +0000
From: "Zhijian Li (Fujitsu)" <lizhijian@...itsu.com>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: Bruno Prémont <bonbons@...ux-vserver.org>, Jiri Kosina
	<jikos@...nel.org>, Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	"linux-input@...r.kernel.org" <linux-input@...r.kernel.org>
Subject: Re: [PATCH v3 1/4] HID: hid-picolcd*: Convert sprintf/scnprintf to
 sysfs_emit/sysfs_emit_at



On 19/03/2024 02:17, Christophe JAILLET wrote:
> Le 18/03/2024 à 02:28, Li Zhijian a écrit :
>> Per filesystems/sysfs.rst, show() should only use sysfs_emit()
>> or sysfs_emit_at() when formatting the value to be returned to user space.
>>
>> coccinelle complains that there are still a couple of functions that use
>> snprintf(). Convert them to sysfs_emit().
>>
>> scnprintf() will be converted as weel if they have.
>>
>> Generally, this patch is generated by
>> make coccicheck M=<path/to/file> MODE=patch \
>> COCCI=scripts/coccinelle/api/device_attr_show.cocci
>>
>> No functional change intended
>>
>> CC: "Bruno Prémont" <bonbons@...ux-vserver.org>
>> CC: Jiri Kosina <jikos@...nel.org>
>> CC: Benjamin Tissoires <benjamin.tissoires@...hat.com>
>> CC: linux-input@...r.kernel.org
>> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
>> ---
>> V3:
>>     Covert more file(drivers/hid/hid-picolcd_fb.c) as suggested by Bruno
>>
>> This is a part of the work "Fix coccicheck device_attr_show warnings"[1]
>> Split them per subsystem so that the maintainer can review it easily
>> [1] https://lore.kernel.org/lkml/20240116041129.3937800-1-lizhijian@fujitsu.com/
>> Signed-off-by: Li Zhijian <lizhijian@...itsu.com>
>> ---
>>   drivers/hid/hid-picolcd_core.c | 6 +++---
>>   drivers/hid/hid-picolcd_fb.c   | 4 ++--
>>   2 files changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/hid/hid-picolcd_core.c b/drivers/hid/hid-picolcd_core.c
>> index bbda231a7ce3..fa46fb6eab3f 100644
>> --- a/drivers/hid/hid-picolcd_core.c
>> +++ b/drivers/hid/hid-picolcd_core.c
>> @@ -256,9 +256,9 @@ static ssize_t picolcd_operation_mode_show(struct device *dev,
>>       struct picolcd_data *data = dev_get_drvdata(dev);
>>       if (data->status & PICOLCD_BOOTLOADER)
>> -        return snprintf(buf, PAGE_SIZE, "[bootloader] lcd\n");
>> +        return sysfs_emit(buf, "[bootloader] lcd\n");
>>       else
>> -        return snprintf(buf, PAGE_SIZE, "bootloader [lcd]\n");
>> +        return sysfs_emit(buf, "bootloader [lcd]\n");
>>   }
>>   static ssize_t picolcd_operation_mode_store(struct device *dev,
>> @@ -301,7 +301,7 @@ static ssize_t picolcd_operation_mode_delay_show(struct device *dev,
>>   {
>>       struct picolcd_data *data = dev_get_drvdata(dev);
>> -    return snprintf(buf, PAGE_SIZE, "%hu\n", data->opmode_delay);
>> +    return sysfs_emit(buf, "%hu\n", data->opmode_delay);
>>   }
>>   static ssize_t picolcd_operation_mode_delay_store(struct device *dev,
>> diff --git a/drivers/hid/hid-picolcd_fb.c b/drivers/hid/hid-picolcd_fb.c
>> index d7dddd99d325..369c78d70e66 100644
>> --- a/drivers/hid/hid-picolcd_fb.c
>> +++ b/drivers/hid/hid-picolcd_fb.c
>> @@ -424,9 +424,9 @@ static ssize_t picolcd_fb_update_rate_show(struct device *dev,
> 
> Hi,
> 
> just above we have:
>      for (i = 1; i <= PICOLCDFB_UPDATE_RATE_LIMIT; i++)
> 
>>           if (ret >= PAGE_SIZE)
>>               break;
> 
> and PICOLCDFB_UPDATE_RATE_LIMIT is 10, so it is not possible to have ret >= PAGE_SIZE. Should it happen, sysfs_emit_at() handles it.
> So, this test can also be removed, IMHO.

Good catch, i will update it.


Thanks
Zhijian

> 
> CJ
> 
>>           else if (i == fb_update_rate)
>> -            ret += scnprintf(buf+ret, PAGE_SIZE-ret, "[%u] ", i);
>> +            ret += sysfs_emit_at(buf, ret, "[%u] ", i);
>>           else
>> -            ret += scnprintf(buf+ret, PAGE_SIZE-ret, "%u ", i);
>> +            ret += sysfs_emit_at(buf, ret, "%u ", i);
>>       if (ret > 0)
>>           buf[min(ret, (size_t)PAGE_SIZE)-1] = '\n';
>>       return ret;
>