Re: [PATCH v4 09/10] gpio: Add a driver for Cadence I3C GPIO expander

[Boris Brezillon]

Hi Linus,

I realize I never replied to this review.

On Thu, 26 Apr 2018 10:44:26 +0200
Linus Walleij <linus.walleij@xxxxxxxxxx> wrote:

> On Fri, Mar 30, 2018 at 9:47 AM, Boris Brezillon
> <boris.brezillon@xxxxxxxxxxx> wrote:
> 
> > Add a driver for Cadence I3C GPIO expander.
> >
> > Signed-off-by: Boris Brezillon <boris.brezillon@xxxxxxxxxxx>  
> 
> This is pretty much OK, and I don't want to raise the bar
> even higher for you to get this code into the kernel, so:
> Acked-by: Linus Walleij <linus.walleij@xxxxxxxxxx>

Thanks.

> 
> The following is an observation for future improvement:
> 
> > +static int cdns_i3c_gpio_read_reg(struct cdns_i3c_gpio *gpioc, u8 reg,
> > +                                 u8 *val)
> > +{
> > +       struct i3c_priv_xfer xfers[] = {
> > +               {
> > +                       .len = sizeof(reg),
> > +                       .data.out = &reg,
> > +               },
> > +               {
> > +                       .rnw = true,
> > +                       .len = sizeof(*val),
> > +                       .data.in = val,
> > +               },
> > +       };
> > +
> > +       return i3c_device_do_priv_xfers(gpioc->i3cdev, xfers,
> > +                                       ARRAY_SIZE(xfers));
> > +}
> > +
> > +static int cdns_i3c_gpio_write_reg(struct cdns_i3c_gpio *gpioc, u8 reg,
> > +                                  u8 val)
> > +{
> > +       struct i3c_priv_xfer xfers[] = {
> > +               {
> > +                       .len = sizeof(reg),
> > +                       .data.out = &reg,
> > +               },
> > +               {
> > +                       .len = sizeof(val),
> > +                       .data.out = &val,
> > +               },
> > +       };
> > +
> > +       return i3c_device_do_priv_xfers(gpioc->i3cdev, xfers,
> > +                                       ARRAY_SIZE(xfers));
> > +}  
> 
> This is starting to resemble
> drivers/base/regmap/regmap-i2c.c
> 
> Maybe we should very quickly add regmap-i3c.c as this
> infrastructre has had a great positive effect on may kernel
> subsystems.

Yes I considered that too, I was just waiting for at least one
other user before adding this regmap-i3c implementation.

> 
> > +static int cdns_i3c_gpio_get_direction(struct gpio_chip *g, unsigned offset)
> > +{
> > +       struct cdns_i3c_gpio *gpioc = gpioc_to_cdns_gpioc(g);
> > +
> > +       return gpioc->dir & BIT(offset);  
> 
> I would:
> 
> return !!(gpioc->dir & BIT(offset));
> 
> So you clamp it to bit 0.

Will fix that in my v5.

Thanks for your review.

Boris