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SubjectRe: [PATCH v4 09/10] gpio: Add a driver for Cadence I3C GPIO expander
On Fri, Mar 30, 2018 at 9:47 AM, Boris Brezillon
<boris.brezillon@bootlin.com> wrote:

> Add a driver for Cadence I3C GPIO expander.
>
> Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>

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@linaro.org>

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.

> +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.

Yours,
Linus Walleij

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