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Subject: Re: [PATCH 1/2] hwmon: (ucd9000) Add gpio chip interface
To:     Eddie James <eajames@linux.vnet.ibm.com>,
        linux-hwmon@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, jdelvare@suse.com, joel@jms.id.au,
        Christopher Bostic <cbostic@linux.vnet.ibm.com>,
        Andrew Jeffery <andrew@aj.id.au>
References: <1520623196-9534-1-git-send-email-eajames@linux.vnet.ibm.com>
 <1520623196-9534-2-git-send-email-eajames@linux.vnet.ibm.com>
From:   Guenter Roeck <linux@roeck-us.net>
Message-ID: <39df66cf-2580-5e49-17b5-2187469b5d44@roeck-us.net>
Date:   Sat, 10 Mar 2018 08:44:46 -0800
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On 03/09/2018 11:19 AM, Eddie James wrote:
> From: Christopher Bostic <cbostic@linux.vnet.ibm.com>
> 
> Add a struct gpio_chip and define some methods so that this device's
> I/O can be accessed via /sys/class/gpio.
> 
> Signed-off-by: Christopher Bostic <cbostic@linux.vnet.ibm.com>
> Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
> Signed-off-by: Eddie James <eajames@linux.vnet.ibm.com>
> ---
>   drivers/hwmon/pmbus/ucd9000.c | 220 ++++++++++++++++++++++++++++++++++++++++++
>   1 file changed, 220 insertions(+)
> 
> diff --git a/drivers/hwmon/pmbus/ucd9000.c b/drivers/hwmon/pmbus/ucd9000.c
> index b74dbec..e3a507f 100644
> --- a/drivers/hwmon/pmbus/ucd9000.c
> +++ b/drivers/hwmon/pmbus/ucd9000.c
> @@ -27,6 +27,7 @@
>   #include <linux/slab.h>
>   #include <linux/i2c.h>
>   #include <linux/pmbus.h>
> +#include <linux/gpio.h>
>   #include "pmbus.h"
>   
>   enum chips { ucd9000, ucd90120, ucd90124, ucd90160, ucd9090, ucd90910 };
> @@ -35,8 +36,18 @@
>   #define UCD9000_NUM_PAGES		0xd6
>   #define UCD9000_FAN_CONFIG_INDEX	0xe7
>   #define UCD9000_FAN_CONFIG		0xe8
> +#define UCD9000_GPIO_SELECT		0xfa
> +#define UCD9000_GPIO_CONFIG		0xfb
>   #define UCD9000_DEVICE_ID		0xfd
>   
> +/* GPIO CONFIG bits */
> +#define UCD9000_GPIO_CONFIG_ENABLE	BIT(0)
> +#define UCD9000_GPIO_CONFIG_OUT_ENABLE	BIT(1)
> +#define UCD9000_GPIO_CONFIG_OUT_VALUE	BIT(2)
> +#define UCD9000_GPIO_CONFIG_STATUS	BIT(3)
> +#define UCD9000_GPIO_INPUT		0
> +#define UCD9000_GPIO_OUTPUT		1
> +
>   #define UCD9000_MON_TYPE(x)	(((x) >> 5) & 0x07)
>   #define UCD9000_MON_PAGE(x)	((x) & 0x0f)
>   
> @@ -47,9 +58,15 @@
>   
>   #define UCD9000_NUM_FAN		4
>   
> +#define UCD9000_GPIO_NAME_LEN	16
> +#define UCD9090_NUM_GPIOS	23
> +#define UCD901XX_NUM_GPIOS	26
> +#define UCD90910_NUM_GPIOS	26
> +
>   struct ucd9000_data {
>   	u8 fan_data[UCD9000_NUM_FAN][I2C_SMBUS_BLOCK_MAX];
>   	struct pmbus_driver_info info;
> +	struct gpio_chip gpio;
>   };
>   #define to_ucd9000_data(_info) container_of(_info, struct ucd9000_data, info)
>   
> @@ -149,6 +166,168 @@ static int ucd9000_read_byte_data(struct i2c_client *client, int page, int reg)
>   };
>   MODULE_DEVICE_TABLE(of, ucd9000_of_match);
>   
> +static int ucd9000_gpio_read_config(struct i2c_client *client,
> +				    unsigned int offset)
> +{
> +	int ret;
> +
> +	/* No page set required */
> +	ret = i2c_smbus_write_byte_data(client, UCD9000_GPIO_SELECT, offset);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to select GPIO %d: %d\n", offset,
> +			ret);
> +

I am not a fan of kernel log error messages outside the probe function.
Please consider dropping those or making it dev_dbg.

Would it make sense to cache those values ?

> +		return ret;
> +	}
> +
> +	return i2c_smbus_read_byte_data(client, UCD9000_GPIO_CONFIG);
> +}
> +
> +static int ucd9000_gpio_get(struct gpio_chip *gc, unsigned int offset)
> +{
> +	struct i2c_client *client  = gpiochip_get_data(gc);
> +	int ret;
> +
> +	ret = ucd9000_gpio_read_config(client, offset);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to read GPIO %d config: %d\n",
> +			offset, ret);
> +
... even more so if a single error can result in multiple error messages.

> +		return ret;
> +	}
> +
> +	return !!(ret & UCD9000_GPIO_CONFIG_STATUS);
> +}
> +
> +static void ucd9000_gpio_set(struct gpio_chip *gc, unsigned int offset,
> +			     int value)
> +{
> +	struct i2c_client *client = gpiochip_get_data(gc);
> +	int ret;
> +
> +	ret = ucd9000_gpio_read_config(client, offset);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to read GPIO %d config: %d\n",
> +			offset, ret);
> +
> +		return;
> +	}
> +
> +	if (value) {
> +		if (ret & UCD9000_GPIO_CONFIG_STATUS)
> +			return;
> +
> +		ret |= UCD9000_GPIO_CONFIG_STATUS;
> +	} else {
> +		if (!(ret & UCD9000_GPIO_CONFIG_STATUS))
> +			return;
> +
> +		ret &= ~UCD9000_GPIO_CONFIG_STATUS;
> +	}
> +
> +	ret |= UCD9000_GPIO_CONFIG_ENABLE;
> +
> +	/* Page set not required */
> +	ret = i2c_smbus_write_byte_data(client, UCD9000_GPIO_CONFIG, ret);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to write GPIO %d config: %d\n",
> +			offset, ret);
> +
> +		return;
> +	}
> +
> +	ret &= ~UCD9000_GPIO_CONFIG_ENABLE;
> +
> +	ret = i2c_smbus_write_byte_data(client, UCD9000_GPIO_CONFIG, ret);
> +	if (ret < 0)
> +		dev_err(&client->dev, "Failed to write GPIO %d config: %d\n",
> +			offset, ret);
> +}
> +
> +static int ucd9000_gpio_get_direction(struct gpio_chip *gc,
> +				      unsigned int offset)
> +{
> +	struct i2c_client *client = gpiochip_get_data(gc);
> +	int ret;
> +
> +	ret = ucd9000_gpio_read_config(client, offset);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to read GPIO %d config: %d\n",
> +			offset, ret);
> +
> +		return ret;
> +	}
> +
> +	return !(ret & UCD9000_GPIO_CONFIG_OUT_ENABLE);
> +}
> +
> +static int ucd9000_gpio_set_direction(struct gpio_chip *gc,
> +				      unsigned int offset, bool direction_out,
> +				      int requested_out)
> +{
> +	struct i2c_client *client = gpiochip_get_data(gc);
> +	int ret, config, out_val;
> +
> +	ret = ucd9000_gpio_read_config(client, offset);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "failed to read GPIO %d config: %d\n",
> +			offset, ret);
> +
> +		return ret;
> +	}
> +
> +	if (direction_out) {
> +		out_val = requested_out ? UCD9000_GPIO_CONFIG_OUT_VALUE : 0;
> +
> +		if (ret & UCD9000_GPIO_CONFIG_OUT_ENABLE) {
> +			if ((ret & UCD9000_GPIO_CONFIG_OUT_VALUE) == out_val)
> +				return 0;
> +		} else {
> +			ret |= UCD9000_GPIO_CONFIG_OUT_ENABLE;
> +		}
> +
> +		if (out_val)
> +			ret |= UCD9000_GPIO_CONFIG_OUT_VALUE;
> +		else
> +			ret &= ~UCD9000_GPIO_CONFIG_OUT_VALUE;
> +
> +	} else {
> +		if (!(ret & UCD9000_GPIO_CONFIG_OUT_ENABLE))
> +			return 0;
> +
> +		ret &= ~UCD9000_GPIO_CONFIG_OUT_ENABLE;
> +	}
> +
> +	ret |= UCD9000_GPIO_CONFIG_ENABLE;
> +	config = ret;
> +
> +	/* Page set not required */
> +	ret = i2c_smbus_write_byte_data(client, UCD9000_GPIO_CONFIG, config);
> +	if (ret < 0) {
> +		dev_err(&client->dev, "Failed to write GPIO %d config: %d\n",
> +			offset, ret);
> +
> +		return ret;
> +	}
> +
> +	config &= ~UCD9000_GPIO_CONFIG_ENABLE;
> +
> +	return i2c_smbus_write_byte_data(client, UCD9000_GPIO_CONFIG, config);
> +}
> +
> +static int ucd9000_gpio_direction_input(struct gpio_chip *gc,
> +					unsigned int offset)
> +{
> +	return ucd9000_gpio_set_direction(gc, offset, UCD9000_GPIO_INPUT, 0);
> +}
> +
> +static int ucd9000_gpio_direction_output(struct gpio_chip *gc,
> +					 unsigned int offset, int val)
> +{
> +	return ucd9000_gpio_set_direction(gc, offset, UCD9000_GPIO_OUTPUT,
> +					  val);
> +}
> +
>   static int ucd9000_probe(struct i2c_client *client,
>   			 const struct i2c_device_id *id)
>   {
> @@ -263,6 +442,47 @@ static int ucd9000_probe(struct i2c_client *client,
>   		  | PMBUS_HAVE_FAN34 | PMBUS_HAVE_STATUS_FAN34;
>   	}
>   
> +	/*
> +	 * Note:
> +	 *
> +	 * Pinmux support has not been added to the new gpio_chip.
> +	 * This support should be added when possible given the mux
> +	 * behavior of these IO devices.
> +	 */
> +	data->gpio.label = (const char *)&client->name;
> +	data->gpio.get_direction = ucd9000_gpio_get_direction;
> +	data->gpio.direction_input = ucd9000_gpio_direction_input;
> +	data->gpio.direction_output = ucd9000_gpio_direction_output;
> +	data->gpio.get = ucd9000_gpio_get;
> +	data->gpio.set = ucd9000_gpio_set;
> +	data->gpio.can_sleep = 1;
> +	data->gpio.base = -1;
> +

Also set of_node ?

> +	/* No default case. No data available for ucd9000. */
> +	switch (mid->driver_data) {
> +	case ucd9090:
> +		data->gpio.ngpio = UCD9090_NUM_GPIOS;
> +		break;
> +	case ucd90120:
> +	case ucd90124:
> +	case ucd90160:
> +		data->gpio.ngpio = UCD901XX_NUM_GPIOS;
> +		break;
> +	case ucd90910:
> +		data->gpio.ngpio = UCD90910_NUM_GPIOS;
> +		break;

Why not:

	default:
		break;

instead of the comment above ?

> +	}
> +
> +	data->gpio.parent = &client->dev;
> +	data->gpio.owner = THIS_MODULE;
> +

Since there are chips with no gpio support (ngpio=0), it would be better
to make the gpio registration conditional.

> +	ret = devm_gpiochip_add_data(&client->dev, &data->gpio, client);
> +	if (ret) {
> +		data->gpio.parent = NULL;
> +		dev_warn(&client->dev, "Could not add gpiochip: %d\n", ret);

Either dev_warn and ignore the error, or dev_err. Either case setting data->gpio.parent
to NULL should be unnecessary.

> +		return ret;
> +	}
> +
>   	return pmbus_do_probe(client, mid, info);
>   }
>   
>