linux-kernel - Re: [PATCH 3/3] bus: mhi: replace snprintf in show functions with sysfs

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Date:   Mon, 18 Oct 2021 21:30:41 -0700
From:   Hemant Kumar <hemantk@...eaurora.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>,
        Greg KH <gregkh@...uxfoundation.org>
Cc:     Joe Perches <joe@...ches.com>, bbhatt@...eaurora.org,
        loic.poulain@...aro.org, wangqing@...o.com, mhi@...ts.linux.dev,
        linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Manivannan Sadhasivam <mani@...nel.org>
Subject: Re: [PATCH 3/3] bus: mhi: replace snprintf in show functions with
 sysfs_emit



On 10/16/2021 9:15 AM, Manivannan Sadhasivam wrote:
> On Sat, Oct 16, 2021 at 05:07:06PM +0200, Greg KH wrote:
>> On Sat, Oct 16, 2021 at 03:24:17AM -0700, Joe Perches wrote:
>>> On Sat, 2021-10-16 at 09:37 +0200, Greg KH wrote:
>>>> On Sat, Oct 16, 2021 at 12:27:34PM +0530, Manivannan Sadhasivam wrote:
>>>>> From: Qing Wang <wangqing@...o.com>
>>>>> coccicheck complains about the use of snprintf() in sysfs show functions.
>>> []
>>>>> diff --git a/drivers/bus/mhi/core/init.c b/drivers/bus/mhi/core/init.c
>>> []
>>>>> @@ -94,7 +94,7 @@ static ssize_t serial_number_show(struct device *dev,
>>>>>   	struct mhi_device *mhi_dev = to_mhi_device(dev);
>>>>>   	struct mhi_controller *mhi_cntrl = mhi_dev->mhi_cntrl;
>>>>>   
>>>>> -	return snprintf(buf, PAGE_SIZE, "Serial Number: %u\n",
>>>>> +	return sysfs_emit(buf, "Serial Number: %u\n",
>>>>>   			mhi_cntrl->serial_number);
>>>>
>>>> The text "Serial Number: " should not be in here, right?  It's obvious
>>>> this is a serial number, that's what the documentation and file name
>>>> says.  Userspace should not have to parse sysfs files.
>>>
>>> sysfs is ABI right?  Parsing or not, it's what's already there.
>>
>> If no tools rely on this, and we can change it, we should at least try.
>>
>> We can not change ABI if something breaks.  If nothing relies on it,
>> then it is fine to do so.
>>
> 
> Hemant, Bhaumik, do you guys know if there are any possible users (scripts/apps)
> of this ABI? I'm not 100% inclined to change it but if we are _sure_ that there
> are no users yet, then I'm ok with it.

Mani, i dont know if any script being used by any user to parse "Serial 
Number".

Thanks,
Hemant
> 
> Thanks,
> Mani
> 
>> thanks,
>>
>> greg k-h

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