On Mon, Mar 27, 2017 at 8:23 AM, Nandor Han <nandor.han@xxxxxx> wrote:
> This is a simple driver that provides a /sys/class/gpio
> interface for controlling and configuring the GPIO lines.
Use the gpio tools in tools/gpio, use the characcter device.
Do not use sysfs. Change this to reference the tools.
> It does not provide support for chip select or interrupts.
>
> Signed-off-by: Nandor Han <nandor.han@xxxxxx>
> Signed-off-by: Semi Malinen <semi.malinen@xxxxxx>
(...)
> +exar Exar Corporation
Send this as a separate patch to the DT bindings maintainer
(Rob Herring.)
> +static int xra1403_get_byte(struct xra1403 *xra, unsigned int addr)
> +{
> + return spi_w8r8(xra->spi, XRA_READ | (addr << 1));
> +}
> +
> +static int xra1403_get_bit(struct xra1403 *xra, unsigned int addr,
> + unsigned int bit)
> +{
> + int ret;
> +
> + ret = xra1403_get_byte(xra, addr + (bit > 7));
> + if (ret < 0)
> + return ret;
> +
> + return !!(ret & BIT(bit % 8));
> +}
This looks like it can use regmap-spi right off, do you agree?
git grep devm_regmap_init_spi
should give you some examples of how to use it.
If it's not off-the shelf regmap drivers like
drivers/iio/pressure/mpl115_spi.c
give examples of how to make more elaborate custom
SPI transfers with regmap.
> +static int xra1403_set_bit(struct xra1403 *xra, unsigned int addr,
> + unsigned int bit, int value)
> +{
> + int ret;
> + u8 mask;
> + u8 tx[2];
> +
> + addr += bit > 7;
> +
> + mutex_lock(&xra->lock);
> +
> + ret = xra1403_get_byte(xra, addr);
> + if (ret < 0)
> + goto out_unlock;
> +
> + mask = BIT(bit % 8);
> + if (value)
> + value = ret | mask;
> + else
> + value = ret & ~mask;
> +
> + if (value != ret) {
> + tx[0] = addr << 1;
> + tx[1] = value;
> + ret = spi_write(xra->spi, tx, sizeof(tx));
> + } else {
> + ret = 0;
> + }
> +
> +out_unlock:
> + mutex_unlock(&xra->lock);
> +
> + return ret;
> +}
Classical mask-and-set implementation right?
With regmap this becomes simply regmap_update_bits(map, addr, mask, set)
> +static int xra1403_probe(struct spi_device *spi)
> +{
> + struct xra1403 *xra;
> + struct gpio_desc *reset_gpio;
> +
> + xra = devm_kzalloc(&spi->dev, sizeof(*xra), GFP_KERNEL);
> + if (!xra)
> + return -ENOMEM;
> +
> + /* bring the chip out of reset */
> + reset_gpio = gpiod_get_optional(&spi->dev, "reset", GPIOD_OUT_LOW);
> + if (IS_ERR(reset_gpio))
> + dev_warn(&spi->dev, "could not get reset-gpios\n");
> + else if (reset_gpio)
> + gpiod_put(reset_gpio);
I don't think you should put it, other than in the remove()
function and in that case you need to have it in the
state container.
> + mutex_init(&xra->lock);
> +
> + xra->chip.direction_input = xra1403_direction_input;
> + xra->chip.direction_output = xra1403_direction_output;
Please implement .get_direction(). This is very nice to have.
> +static int xra1403_remove(struct spi_device *spi)
> +{
> + struct xra1403 *xra = spi_get_drvdata(spi);
> +
> + gpiochip_remove(&xra->chip);
Use devm_gpiochip_add_data() and this remove is not
needed at all.
> +static int __init xra1403_init(void)
> +{
> + return spi_register_driver(&xra1403_driver);
> +}
> +
> +/*
> + * register after spi postcore initcall and before
> + * subsys initcalls that may rely on these GPIOs
> + */
> +subsys_initcall(xra1403_init);
> +
> +static void __exit xra1403_exit(void)
> +{
> + spi_unregister_driver(&xra1403_driver);
> +}
> +module_exit(xra1403_exit);
This seems like tricksy. Just module_spi_driver()
should be fine don't you think?
Yours,
Linus Walleij
--
To unsubscribe from this list: send the line "unsubscribe devicetree" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
