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SubjectRe: [PATCH] gpio: 74x164: Implement gpiochip.set_multiple()
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On 14/03/2016 11:19 PM, Geert Uytterhoeven wrote:
> This allows to set multiple outputs using a single SPI transfer.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

Reviewed-by: Phil Reid <preid@electromag.com.au>


I do have a general question about GPIO drivers.
pca953x does not update the cached data unless the write operation
was successful. Which I folowed with the implement of set_multiple.
However a number of other drivers update regardless.
eg chip->buffer is updated even if the write_config fails.

What is the preferred approach?

> ---
> drivers/gpio/gpio-74x164.c | 24 ++++++++++++++++++++++++
> 1 file changed, 24 insertions(+)
>
> diff --git a/drivers/gpio/gpio-74x164.c b/drivers/gpio/gpio-74x164.c
> index c81224ff2dca988b..62291a81c97f7140 100644
> --- a/drivers/gpio/gpio-74x164.c
> +++ b/drivers/gpio/gpio-74x164.c
> @@ -75,6 +75,29 @@ static void gen_74x164_set_value(struct gpio_chip *gc,
> mutex_unlock(&chip->lock);
> }
>
> +static void gen_74x164_set_multiple(struct gpio_chip *gc, unsigned long *mask,
> + unsigned long *bits)
> +{
> + struct gen_74x164_chip *chip = gpiochip_get_data(gc);
> + unsigned int i, idx, shift;
> + u8 bank, bankmask;
> +
> + mutex_lock(&chip->lock);
> + for (i = 0, bank = chip->registers - 1; i < chip->registers;
> + i++, bank--) {
> + idx = i / sizeof(*mask);
> + shift = i % sizeof(*mask) * BITS_PER_BYTE;
> + bankmask = mask[idx] >> shift;
> + if (!bankmask)
> + continue;
> +
> + chip->buffer[bank] &= ~bankmask;
> + chip->buffer[bank] |= bankmask & (bits[idx] >> shift);
> + }
> + __gen_74x164_write_config(chip);
> + mutex_unlock(&chip->lock);
> +}
> +
> static int gen_74x164_direction_output(struct gpio_chip *gc,
> unsigned offset, int val)
> {
> @@ -114,6 +137,7 @@ static int gen_74x164_probe(struct spi_device *spi)
> chip->gpio_chip.direction_output = gen_74x164_direction_output;
> chip->gpio_chip.get = gen_74x164_get_value;
> chip->gpio_chip.set = gen_74x164_set_value;
> + chip->gpio_chip.set_multiple = gen_74x164_set_multiple;
> chip->gpio_chip.base = -1;
>
> chip->registers = nregs;
>


--
Regards
Phil Reid

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