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

[Phil Reid]

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+rene...@glider.be>

Reviewed-by: Phil Reid <pr...@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