[...]

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+static int get_gpio_pin_state(struct irq_desc *irq_desc)
+{
+	struct gpio_chip *gc = irq_data_get_irq_chip_data(&irq_desc->irq_data);
+
+	return gc->get(gc, irq_desc->irq_data.hwirq);
+}

[...]

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+	ssize_t	status = get_gpio_pin_state(irq_desc);

`get_gpio_pin_state()` returns an `int`, so I am not sure why `ssize_t` is used here.

I used `ssize_t` because I found gpiolib-sysfs.c uses `ssize_t`

     // drivers/gpio/gpiolib-sysfs.c
     static ssize_t value_show(struct device *dev,
     		struct device_attribute *attr, char *buf)
     {
     	struct gpiod_data *data = dev_get_drvdata(dev);
     	struct gpio_desc *desc = data->desc;
     	ssize_t			status;

     	mutex_lock(&data->mutex);

     	status = gpiod_get_value_cansleep(desc);
         ...
     	return status;
     }

According to the book Advanced Programming in the UNIX Environment by
W. Richard Stevens,
     With the 1990 POSIX.1 standard, the primitive system data type
     ssize_t was introduced to provide the signed return value...

So ssize_t is fairly common, for example, the read and write syscall
return a value of type ssize_t. But I haven't found out why ssize_t is
better int.

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Sorry if I wasn't clear, what prompted me to ask that question is the following:
`gc->get()` returns `int`, `get_gpio_pin_state()` returns `int`, yet you still
save the return value of `get_gpio_pin_state()` into a variable with type
`ssize_t` for no apparent reason. In the example you cited, `ssize_t` is used
because the show() callback of a sysfs attribute must return `ssize_t`, but here,
`interrupt_line_active()` returns `bool`, so I don't see any advantage over a
plain `int`. Anyways, I believe either one is fine, I just found it odd.

I don't understand why "the show() callback of a sysfs attribute
must return `ssize_t`" instead of int. Do you think the rationale
behind it is the same for this case? If yes, using "ssize_t" for
status could be justified.
[...]

Because it was decided that way, `ssize_t` is a better choice for that purpose
than plain `int`. You can see it in include/linux/device.h, that both the
show() and store() methods must return `ssize_t`.

What I'm arguing here, is that there is no reason to use `ssize_t` in this case.
Because `get_gpio_pin_state()` returns `int`. So when you do

ssize_t status = get_gpio_pin_state(...);

then the return value of `get_gpio_pin_state()` (which is an `int`), will be
converted to an `ssize_t`, and saved into `status`. I'm arguing that that is
unnecessary and a plain `int` would work perfectly well in this case. Anyways,
both work fine, I just found the unnecessary use of `ssize_t` here odd.


Regards,
Barnabás Pőcze