Re: [PATCH v2 05/18] gpiolib: cdev: support GPIO_GET_LINE_IOCTL and GPIOLINE_GET_VALUES_IOCTL

[Kent Gibson <warthog618@xxxxxxxxx>]

On Sun, Jul 26, 2020 at 09:12:44AM +0800, Kent Gibson wrote:
> On Sat, Jul 25, 2020 at 11:51:54PM +0300, Andy Shevchenko wrote:
> > On Sat, Jul 25, 2020 at 7:24 AM Kent Gibson <warthog618@xxxxxxxxx> wrote:
> > >

[ snip ]
> > 
> > > +static bool padding_not_zeroed(__u32 *padding, int pad_size)
> > > +{
> > > +       int i, sum = 0;
> > > +
> > > +       for (i = 0; i < pad_size; i++)
> > > +               sum |= padding[i];
> > > +
> > > +       return sum;
> > > +}
> > 
> > Reimplementation of memchr_inv() ?
> > 
> 
> I was hoping to find an existing function, surely checking a region is
> zeroed is a common thing, right?, so this was a place holder as much
> as anything.  Not sure memchr_inv fits the bill, but I'll give it a
> try...
> 

I gave it a try.  It is a good fit functionally, but in my build it
results in a larger object by ~104 bytes.  I assume that is because 
padding_not_zeroed is being inlined, and otherwise optimized, while
memchr_inv calls aren't.

As such I'm inclined to leave it as is - unless there are other
objections.

Cheers,
Kent.