Re: [PATCH] iio: cros_ec: use sysfs_emit() in show callbacks

[David Laight <david.laight.linux@gmail.com>]

On Fri, 13 Nov 2026 01:36:46 +0000
Jonathan Cameron <jic23@kernel.org> wrote:

> On Thu, 12 Nov 2026 22:02:18 +0000
> David Laight <david.laight.linux@gmail.com> wrote:
> 
> > On Thu, 12 Nov 2026 02:04:39 +0000
> > Jonathan Cameron <jic23@kernel.org> wrote:
> >   
> > > On Wed, 11 Nov 2026 16:39:37 +0200
> > > Andy Shevchenko <andriy.shevchenko@intel.com> wrote:
> > >     
> > > > On Wed, Nov 11, 2026 at 07:26:08AM +0000, Di Wu wrote:      
> > > > > Replace sprintf() and snprintf() with sysfs_emit() in the sysfs show
> > > > > and ext_info read callbacks. sysfs_emit() is aware of the sysfs buffer
> > > > > PAGE_SIZE limit and is the preferred helper for show callbacks.        
> > > > 
> > > > Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
> > > > 
> > > > ...
> > > >       
> > > > > -	return sprintf(buf, "%d.%06u\n",
> > > > > -		       latency / 1000,
> > > > > -		       (latency % 1000) * 1000);
> > > > > +	return sysfs_emit(buf, "%d.%06u\n",
> > > > > +			  latency / 1000,
> > > > > +			  (latency % 1000) * 1000);        
> > > > 
> > > > As David said, since you touched these lines, make the less amount of them
> > > > while at it.
> > > > 
> > > > (But no need to resend, usually Jonathan is kind to tweak this small thing.)
> > > >       
> > > Done and applied.
> > > 
> > >     
> > 
> > I just looked at that line again.
> > Why is it multiplying the remainder by 1000?
> > It could be:
> > 	return sysfs_emit(buf, "%d.%03u000\n", latency / 1000, latency % 1000);
> > if the 6 digits after the decimal point are required.  
> 
> Good point, I guess unrelated change that we could have on top.

Indeed.

> Those trailing zeros shouldn't matter.

There is a matching oddity in the set function (just above).
It calls iio_str_to_fixpoint(buf, 1000000, &integer, &fract)
then does latency = integer * 1000 + fract/1000.
Just replace the 100000 by 1000 and you don't need the divide.

iio_str_to_fixpoint() will ignore are extra fractional digits.

Although I'm not at all sure its handling of negative value is correct.
It converts -1.5 to -1/5 and -0.5 to 0/-5.
I can't see how that is useful since i*10+f for both gives -5.

I'd have though that either the fractional part should always be positive
so -1.4 would need converting to -2/6 or it would have the same sign as
the integer part and -1.4 would be converted to -1/-4.

David

> 
> > 
> > David  
>