Re: [PATCH] gpio MIPS/OCTEON: Add a driver for OCTEON's on-chip GPIOpins.

[David Daney]

On 06/20/2013 11:43 AM, Joe Perches wrote:
> On Thu, 2013-06-20 at 11:27 -0700, David Daney wrote:
> > On 06/20/2013 11:18 AM, Joe Perches wrote:
> > > On Thu, 2013-06-20 at 11:10 -0700, David Daney wrote:
> > > > Sorry for not responding earlier, but my e-mail system seems to have
> > > > malfunctioned with respect to this message...
> > > []
> > > > On 06/17/2013 01:51 AM, Linus Walleij wrote:
> > > > > > +static int octeon_gpio_get(struct gpio_chip *chip, unsigned offset)
> > > > > > +{
> > > > > > +       struct octeon_gpio *gpio = container_of(chip, struct octeon_gpio, chip);
> > > > > > +       u64 read_bits = cvmx_read_csr(gpio->register_base + RX_DAT);
> > > > > > +
> > > > > > +       return ((1ull << offset) & read_bits) != 0;
> > > > >
> > > > > A common idiom we use for this is:
> > > > >
> > > > > return !!(read_bits & (1ull << offset));
> > > >
> > > > I hate that idiom, but if its use is a condition of accepting the patch,
> > > > I will change it.
> > >
> > > Or use an even more common idiom and change the
> > > function to return bool and let the compiler do it.
> >
> > ... but it is part of the gpiochip system interface, so it would have to
> > be done kernel wide.
>
> Not really.  It's a local static function.

... which we generate a pointer to, and then assign that pointer to a 
variable with a type defined in the gpiochip system interface.  So If we 
do what you suggest, the result is:

  CC      drivers/gpio/gpio-octeon.o
drivers/gpio/gpio-octeon.c: In function 'octeon_gpio_probe':
drivers/gpio/gpio-octeon.c:113:12: warning: assignment from incompatible 
pointer type [enabled by default]



> > Really I don't like the idea of GPIO lines having Boolean truth values
> > associated with them.  Some represent things that are active-high and
> > others active-low.  Converting the pin voltage being above or below a
> > given threshold to something other than zero or one would in my opinion
> > be confusing.
>
> No worries, just offering options.  Your code, your choice.

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