Re: [PATCH] gpio: 74x164: Implement gpiochip.set_multiple()

From: Phil Reid
Date: Tue Mar 15 2016 - 00:04:46 EST


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@xxxxxxxxx>

Reviewed-by: Phil Reid <preid@xxxxxxxxxxxxxxxxx>


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