Re: [PATCH v3 1/4] staging: iio: ad7816: Switch to the gpio descriptor interface

["Ardelean, Alexandru" <alexandru.Ardelean@analog.com>]

On Fri, 2018-11-09 at 13:05 +0530, Nishad Kamdar wrote:
> Use the gpiod interface for rdwr_pin, convert_pin and busy_pin
> instead of the deprecated old non-descriptor interface.
> 

Patch looks good.
I do have some thoughts about it. See inline.


> Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
> ---
>  drivers/staging/iio/adc/ad7816.c | 80 ++++++++++++++------------------
>  1 file changed, 34 insertions(+), 46 deletions(-)
> 
> diff --git a/drivers/staging/iio/adc/ad7816.c
> b/drivers/staging/iio/adc/ad7816.c
> index bf76a8620bdb..12c4e0ab4713 100644
> --- a/drivers/staging/iio/adc/ad7816.c
> +++ b/drivers/staging/iio/adc/ad7816.c
> @@ -7,7 +7,7 @@
>   */
>  
>  #include <linux/interrupt.h>
> -#include <linux/gpio.h>
> +#include <linux/gpio/consumer.h>
>  #include <linux/device.h>
>  #include <linux/kernel.h>
>  #include <linux/slab.h>
> @@ -44,9 +44,9 @@
>  
>  struct ad7816_chip_info {
>  	struct spi_device *spi_dev;
> -	u16 rdwr_pin;
> -	u16 convert_pin;
> -	u16 busy_pin;
> +	struct gpio_desc *rdwr_pin;
> +	struct gpio_desc *convert_pin;
> +	struct gpio_desc *busy_pin;

Only if you want to do a re-spin, here's an idea.
If you don't want to, feel free to disregard, since your patch is good.

You could compact things a bit; I know this wasn't what the initial code
was doing, but it's an option.

Something like:

enum {
	GPIO_RWDR,
	GPIO_CONVERT,
	GPIO_BUSY,
	__GPIO_MAX,
}

Then, what you end up having is:

 struct ad7816_chip_info {
  	struct spi_device *spi_dev;
 -	u16 rdwr_pin;
 -	u16 convert_pin;
 -	u16 busy_pin;
 +	struct gpio_desc *gpios[__GPIO_MAX];
 

// Continued below


>  	u8  oti_data[AD7816_CS_MAX + 1];
>  	u8  channel_id;	/* 0 always be temperature */
>  	u8  mode;
> @@ -61,28 +61,28 @@ static int ad7816_spi_read(struct ad7816_chip_info
> *chip, u16 *data)
>  	int ret = 0;
>  	__be16 buf;
>  
> -	gpio_set_value(chip->rdwr_pin, 1);
> -	gpio_set_value(chip->rdwr_pin, 0);
> +	gpiod_set_value(chip->rdwr_pin, 1);
> +	gpiod_set_value(chip->rdwr_pin, 0);

Obviously, in the above context, this becomes:
 +	gpiod_set_value(chip->gpios[GPIO_RWDR], 1);
 +	gpiod_set_value(chip->gpios[GPIO_RWDR], 0);

>  	ret = spi_write(spi_dev, &chip->channel_id, sizeof(chip-
> >channel_id));
>  	if (ret < 0) {
>  		dev_err(&spi_dev->dev, "SPI channel setting error\n");
>  		return ret;
>  	}
> -	gpio_set_value(chip->rdwr_pin, 1);
> +	gpiod_set_value(chip->rdwr_pin, 1);
>  
>  	if (chip->mode == AD7816_PD) { /* operating mode 2 */
> -		gpio_set_value(chip->convert_pin, 1);
> -		gpio_set_value(chip->convert_pin, 0);
> +		gpiod_set_value(chip->convert_pin, 1);
> +		gpiod_set_value(chip->convert_pin, 0);
>  	} else { /* operating mode 1 */
> -		gpio_set_value(chip->convert_pin, 0);
> -		gpio_set_value(chip->convert_pin, 1);
> +		gpiod_set_value(chip->convert_pin, 0);
> +		gpiod_set_value(chip->convert_pin, 1);
>  	}
>  
> -	while (gpio_get_value(chip->busy_pin))
> +	while (gpiod_get_value(chip->busy_pin))
>  		cpu_relax();
>  
> -	gpio_set_value(chip->rdwr_pin, 0);
> -	gpio_set_value(chip->rdwr_pin, 1);
> +	gpiod_set_value(chip->rdwr_pin, 0);
> +	gpiod_set_value(chip->rdwr_pin, 1);
>  	ret = spi_read(spi_dev, &buf, sizeof(*data));
>  	if (ret < 0) {
>  		dev_err(&spi_dev->dev, "SPI data read error\n");
> @@ -99,8 +99,8 @@ static int ad7816_spi_write(struct ad7816_chip_info
> *chip, u8 data)
>  	struct spi_device *spi_dev = chip->spi_dev;
>  	int ret = 0;
>  
> -	gpio_set_value(chip->rdwr_pin, 1);
> -	gpio_set_value(chip->rdwr_pin, 0);
> +	gpiod_set_value(chip->rdwr_pin, 1);
> +	gpiod_set_value(chip->rdwr_pin, 0);
>  	ret = spi_write(spi_dev, &data, sizeof(data));
>  	if (ret < 0)
>  		dev_err(&spi_dev->dev, "SPI oti data write error\n");
> @@ -129,10 +129,10 @@ static ssize_t ad7816_store_mode(struct device
> *dev,
>  	struct ad7816_chip_info *chip = iio_priv(indio_dev);
>  
>  	if (strcmp(buf, "full")) {
> -		gpio_set_value(chip->rdwr_pin, 1);
> +		gpiod_set_value(chip->rdwr_pin, 1);
>  		chip->mode = AD7816_FULL;
>  	} else {
> -		gpio_set_value(chip->rdwr_pin, 0);
> +		gpiod_set_value(chip->rdwr_pin, 0);
>  		chip->mode = AD7816_PD;
>  	}
>  
> @@ -345,15 +345,9 @@ static int ad7816_probe(struct spi_device *spi_dev)
>  {
>  	struct ad7816_chip_info *chip;
>  	struct iio_dev *indio_dev;
> -	unsigned short *pins = dev_get_platdata(&spi_dev->dev);
>  	int ret = 0;
>  	int i;
>  
> -	if (!pins) {
> -		dev_err(&spi_dev->dev, "No necessary GPIO platform
> data.\n");
> -		return -EINVAL;
> -	}
> -
>  	indio_dev = devm_iio_device_alloc(&spi_dev->dev, sizeof(*chip));
>  	if (!indio_dev)
>  		return -ENOMEM;
> @@ -364,34 +358,28 @@ static int ad7816_probe(struct spi_device *spi_dev)
>  	chip->spi_dev = spi_dev;
>  	for (i = 0; i <= AD7816_CS_MAX; i++)
>  		chip->oti_data[i] = 203;
> -	chip->rdwr_pin = pins[0];
> -	chip->convert_pin = pins[1];
> -	chip->busy_pin = pins[2];
> -
> -	ret = devm_gpio_request(&spi_dev->dev, chip->rdwr_pin,
> -				spi_get_device_id(spi_dev)->name);
> -	if (ret) {
> -		dev_err(&spi_dev->dev, "Fail to request rdwr gpio PIN
> %d.\n",
> -			chip->rdwr_pin);
> +
> +	chip->rdwr_pin = devm_gpiod_get(&spi_dev->dev, "rdwr", GPIOD_IN);
> +	if (IS_ERR(chip->rdwr_pin)) {
> +		ret = PTR_ERR(chip->rdwr_pin);
> +		dev_err(&spi_dev->dev, "Failed to request rdwr GPIO: %d\n",
> +			ret);
>  		return ret;
>  	}

But the real benefit if this approach comes here.
You could do:

static const char *gpio_names[__GPIO_MAX] = {
	[GPIO_RWDR] = "rwdr",
	[GPIO_CONVERT] = "convert",
	[GPIO_BUSY] = "busy",
};

// code for patch2	
bool have_busy_pin = (chip->id == ID_AD7816 || chip->id == ID_AD7817);
// end code for patch2	


for (i = 0; i < __GPIO_MAX; i++) {
// code for patch2	
	if (i == GPIO_BUSY && !have_busy_pin)
		continue;
// end code for patch2	

	chip->gpios[i] = devm_gpiod_get(&spi_dev->dev, gpio_names[i], 
					GPIOD_IN);
	if (IS_ERR(chip->gpios[i])) {
		ret = PTR_ERR(chip->gpios[i]);
		dev_err(&spi_dev->dev, "Failed to request rdwr GPIO: %d\n",
			ret;
		return ret;
	}
}

Then, in your patch2 (i.e " staging: iio: ad7816: Do not use busy_pin in
case of AD7818"), what you could do, is to add that code (along with the
other ID code).

And finaly what you could do in patch2, is:

	while (chip->gpios[GPIO_BUSY] &&
	       gpiod_get_value(chip->busy_pin))
		cpu_relax();



> -	gpio_direction_input(chip->rdwr_pin);
> -	ret = devm_gpio_request(&spi_dev->dev, chip->convert_pin,
> -				spi_get_device_id(spi_dev)->name);
> -	if (ret) {
> -		dev_err(&spi_dev->dev, "Fail to request convert gpio PIN
> %d.\n",
> -			chip->convert_pin);
> +	chip->convert_pin = devm_gpiod_get(&spi_dev->dev, "convert",
> GPIOD_IN);
> +	if (IS_ERR(chip->convert_pin)) {
> +		ret = PTR_ERR(chip->convert_pin);
> +		dev_err(&spi_dev->dev, "Failed to request convert GPIO:
> %d\n",
> +			ret);
>  		return ret;
>  	}
> -	gpio_direction_input(chip->convert_pin);
> -	ret = devm_gpio_request(&spi_dev->dev, chip->busy_pin,
> -				spi_get_device_id(spi_dev)->name);
> -	if (ret) {
> -		dev_err(&spi_dev->dev, "Fail to request busy gpio PIN
> %d.\n",
> -			chip->busy_pin);
> +	chip->busy_pin = devm_gpiod_get(&spi_dev->dev, "busy", GPIOD_IN);
> +	if (IS_ERR(chip->busy_pin)) {
> +		ret = PTR_ERR(chip->busy_pin);
> +		dev_err(&spi_dev->dev, "Failed to request busy GPIO: %d\n",
> +			ret);
>  		return ret;
>  	}
> -	gpio_direction_input(chip->busy_pin);
>  
>  	indio_dev->name = spi_get_device_id(spi_dev)->name;
>  	indio_dev->dev.parent = &spi_dev->dev;