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

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Date:   Sat, 16 Oct 2021 21:45:31 +0530
From:   Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     Joe Perches <joe@...ches.com>, hemantk@...eaurora.org,
        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 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.

Thanks,
Mani

> thanks,
> 
> greg k-h