Re: [PATCH v4 2/2] i2c: mux: ltc4306: LTC4306 and LTC4305 I2C multiplexer/switch

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On 10.04.2017 22:04, Linus Walleij wrote:
On Wed, Apr 5, 2017 at 3:07 PM,  <michael.hennerich@xxxxxxxxxx> wrote:

From: Michael Hennerich <michael.hennerich@xxxxxxxxxx>

This patch adds support for the Analog Devices / Linear Technology
LTC4306 and LTC4305 4/2 Channel I2C Bus Multiplexer/Switches.
The LTC4306 optionally provides two general purpose input/output pins
(GPIOs) that can be configured as logic inputs, opendrain outputs or
push-pull outputs via the generic GPIOLIB framework.

Signed-off-by: Michael Hennerich <michael.hennerich@xxxxxxxxxx>

Okay!

Hi Linus,

Thanks for your review.
Comments below.


+#include <linux/device.h>
+#include <linux/gpio.h>
+#include <linux/gpio/consumer.h>
+#include <linux/gpio/driver.h>

Why are you including all these?
Normally a GPIO driver should just include
<linux/gpio/driver.h>

Well - this driver is also a gpio consumer.
But right I can drop gpio.h, and while gpio/driver.h also includes device.h - we don't need it here as well.


+#include <linux/i2c-mux.h>
+#include <linux/i2c.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/regmap.h>
+#include <linux/slab.h>

+static int ltc4306_gpio_get(struct gpio_chip *chip, unsigned int offset)
+{
+       struct ltc4306 *data = gpiochip_get_data(chip);
+       unsigned int val;
+       int ret;
+
+       ret = regmap_read(data->regmap, LTC_REG_CONFIG, &val);
+       if (ret < 0)
+               return ret;
+
+       return (val & BIT(1 - offset));

Do this:

return !!(val & BIT(1 - offset));

So you clamp the return value to [0,1]

That's what I had in a previous version of the patch.
Then I noticed gpiolib is also doing this.
Anyways I'll add it back.


+static int ltc4306_gpio_set_config(struct gpio_chip *chip,
+                                  unsigned int offset, unsigned long config)
+{
+       struct ltc4306 *data = gpiochip_get_data(chip);
+       unsigned int val;
+
+       switch (pinconf_to_config_param(config)) {
+       case PIN_CONFIG_DRIVE_OPEN_DRAIN:
+               val = 0;
+               break;
+       case PIN_CONFIG_DRIVE_PUSH_PULL:
+               val = BIT(4 - offset);
+               break;
+       default:
+               return -ENOTSUPP;
+       }
+
+       return regmap_update_bits(data->regmap, LTC_REG_MODE,
+                                 BIT(4 - offset), val);
+}

Nice!

+       data->gpiochip.label = dev_name(dev);
+       data->gpiochip.base = -1;
+       data->gpiochip.ngpio = data->chip->num_gpios;
+       data->gpiochip.parent = dev;
+       data->gpiochip.can_sleep = true;
+       data->gpiochip.direction_input = ltc4306_gpio_direction_input;
+       data->gpiochip.direction_output = ltc4306_gpio_direction_output;
+       data->gpiochip.get = ltc4306_gpio_get;
+       data->gpiochip.set = ltc4306_gpio_set;
+       data->gpiochip.set_config = ltc4306_gpio_set_config;
+       data->gpiochip.owner = THIS_MODULE;

Please implement .get_direction().
This is very helpful to userspace, have you tested to use tools/gpio/*
from the kernel? Like lsgpio?

Ok - convinced me.


Yours,
Linus Walleij


--
Greetings,
Michael

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