Re: [PATCH v2] iio: stx104: Add GPIO support for the Apex Embedded Systems STX104

[Jonathan Cameron <jic23@kernel.org>]

On 03/06/16 18:42, William Breathitt Gray wrote:
> The Apex Embedded Systems STX104 device features eight lines of digital
> I/O (four digital inputs and four digital outputs). This patch adds GPIO
> support for these eight lines of digital I/O via GPIOLIB.
> 
> Signed-off-by: William Breathitt Gray <vilhelm.gray@gmail.com>
This is a gpio chip support patch.  Even though the driver is in IIO we
need to get it reviewed by appropriate maintainer.

Cc'd Linus, Alexandre and the list.

> ---
> Changes in v2:
>   - Change GPIOLIB Kconfig selection to a dependency for the STX104 Kconfig
>     option; STX104 should only be available to systems configured for GPIOLIB
> 
>  drivers/iio/dac/Kconfig  |  11 +++--
>  drivers/iio/dac/stx104.c | 118 ++++++++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 122 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/dac/Kconfig b/drivers/iio/dac/Kconfig
> index 61d5008..35a3d49 100644
> --- a/drivers/iio/dac/Kconfig
> +++ b/drivers/iio/dac/Kconfig
> @@ -246,13 +246,14 @@ config MCP4922
>  	  will be called mcp4922.
>  
>  config STX104
> -	tristate "Apex Embedded Systems STX104 DAC driver"
> +	tristate "Apex Embedded Systems STX104 driver"
>  	depends on ISA
> +	depends on GPIOLIB
>  	help
> -	  Say yes here to build support for the 2-channel DAC on the Apex
> -	  Embedded Systems STX104 integrated analog PC/104 card. The base port
> -	  addresses for the devices may be configured via the "base" module
> -	  parameter array.
> +	  Say yes here to build support for the 2-channel DAC and GPIO on the
> +	  Apex Embedded Systems STX104 integrated analog PC/104 card. The base
> +	  port addresses for the devices may be configured via the base array
> +	  module parameter.
>  
>  config VF610_DAC
>  	tristate "Vybrid vf610 DAC driver"
> diff --git a/drivers/iio/dac/stx104.c b/drivers/iio/dac/stx104.c
> index 174f4b7..dc445cf 100644
> --- a/drivers/iio/dac/stx104.c
> +++ b/drivers/iio/dac/stx104.c
> @@ -14,6 +14,7 @@
>  #include <linux/bitops.h>
>  #include <linux/device.h>
>  #include <linux/errno.h>
> +#include <linux/gpio/driver.h>
>  #include <linux/iio/iio.h>
>  #include <linux/iio/types.h>
>  #include <linux/io.h>
> @@ -21,6 +22,7 @@
>  #include <linux/isa.h>
>  #include <linux/module.h>
>  #include <linux/moduleparam.h>
> +#include <linux/spinlock.h>
>  
>  #define STX104_NUM_CHAN 2
>  
> @@ -56,6 +58,20 @@ struct stx104_iio {
>  	unsigned base;
>  };
>  
> +/**
> + * struct stx104_gpio - GPIO device private data structure
> + * @chip:	instance of the gpio_chip
> + * @lock:	synchronization lock to prevent I/O race conditions
> + * @base:	base port address of the GPIO device
> + * @out_state:	output bits state
> + */
> +struct stx104_gpio {
> +	struct gpio_chip chip;
> +	spinlock_t lock;
> +	unsigned int base;
> +	unsigned int out_state;
> +};
> +
>  static int stx104_read_raw(struct iio_dev *indio_dev,
>  	struct iio_chan_spec const *chan, int *val, int *val2, long mask)
>  {
> @@ -95,15 +111,74 @@ static const struct iio_chan_spec stx104_channels[STX104_NUM_CHAN] = {
>  	STX104_CHAN(1)
>  };
>  
> +static int stx104_gpio_get_direction(struct gpio_chip *chip,
> +	unsigned int offset)
> +{
> +	if (offset < 4)
> +		return 1;
> +
> +	return 0;
> +}
> +
> +static int stx104_gpio_direction_input(struct gpio_chip *chip,
> +	unsigned int offset)
> +{
> +	return 0;
> +}
> +
> +static int stx104_gpio_direction_output(struct gpio_chip *chip,
> +	unsigned int offset, int value)
> +{
> +	return 0;
Not return an error if the relevant pin can't be an output?
> +}
> +
> +static int stx104_gpio_get(struct gpio_chip *chip, unsigned int offset)
> +{
> +	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
> +
> +	if (offset >= 4)
> +		return -EINVAL;
> +
> +	return !!(inb(stx104gpio->base) & BIT(offset));
> +}
> +
> +static void stx104_gpio_set(struct gpio_chip *chip, unsigned int offset,
> +	int value)
> +{
> +	struct stx104_gpio *const stx104gpio = gpiochip_get_data(chip);
> +	const unsigned int mask = BIT(offset) >> 4;
> +	unsigned long flags;
> +
> +	if (offset < 4)
> +		return;
> +
> +	spin_lock_irqsave(&stx104gpio->lock, flags);
> +
> +	if (value)
> +		stx104gpio->out_state |= mask;
> +	else
> +		stx104gpio->out_state &= ~mask;
> +
> +	outb(stx104gpio->out_state, stx104gpio->base);
> +
> +	spin_unlock_irqrestore(&stx104gpio->lock, flags);
> +}
> +
>  static int stx104_probe(struct device *dev, unsigned int id)
>  {
>  	struct iio_dev *indio_dev;
>  	struct stx104_iio *priv;
> +	struct stx104_gpio *stx104gpio;
> +	int err;
>  
>  	indio_dev = devm_iio_device_alloc(dev, sizeof(*priv));
>  	if (!indio_dev)
>  		return -ENOMEM;
>  
> +	stx104gpio = devm_kzalloc(dev, sizeof(*stx104gpio), GFP_KERNEL);
> +	if (!stx104gpio)
> +		return -ENOMEM;
> +
>  	if (!devm_request_region(dev, base[id], STX104_EXTENT,
>  		dev_name(dev))) {
>  		dev_err(dev, "Unable to lock port addresses (0x%X-0x%X)\n",
> @@ -124,14 +199,53 @@ static int stx104_probe(struct device *dev, unsigned int id)
>  	outw(0, base[id] + 4);
>  	outw(0, base[id] + 6);
>  
> -	return devm_iio_device_register(dev, indio_dev);
> +	err = devm_iio_device_register(dev, indio_dev);
> +	if (err) {
> +		dev_err(dev, "IIO device registering failed (%d)\n", err);
> +		return err;
> +	}
> +
> +	stx104gpio->chip.label = dev_name(dev);
> +	stx104gpio->chip.parent = dev;
> +	stx104gpio->chip.owner = THIS_MODULE;
> +	stx104gpio->chip.base = -1;
> +	stx104gpio->chip.ngpio = 8;
> +	stx104gpio->chip.get_direction = stx104_gpio_get_direction;
> +	stx104gpio->chip.direction_input = stx104_gpio_direction_input;
> +	stx104gpio->chip.direction_output = stx104_gpio_direction_output;
> +	stx104gpio->chip.get = stx104_gpio_get;
> +	stx104gpio->chip.set = stx104_gpio_set;
> +	stx104gpio->base = base[id] + 3;
> +	stx104gpio->out_state = 0x0;
> +
> +	spin_lock_init(&stx104gpio->lock);
> +
> +	dev_set_drvdata(dev, stx104gpio);
> +
> +	err = gpiochip_add_data(&stx104gpio->chip, stx104gpio);
> +	if (err) {
> +		dev_err(dev, "GPIO registering failed (%d)\n", err);
> +		return err;
> +	}
> +
> +	return 0;
> +}
> +
> +static int stx104_remove(struct device *dev, unsigned int id)
> +{
> +	struct stx104_gpio *const stx104gpio = dev_get_drvdata(dev);
> +
> +	gpiochip_remove(&stx104gpio->chip);
> +
> +	return 0;
>  }
>  
>  static struct isa_driver stx104_driver = {
>  	.probe = stx104_probe,
>  	.driver = {
>  		.name = "stx104"
> -	}
> +	},
> +	.remove = stx104_remove
>  };
>  
>  static void __exit stx104_exit(void)
>