gpiolib: cdev: Flag invalid GPIOs as used
When reporting the state of a GPIO to userspace, we never check
for the actual validity of the line, meaning we report invalid
lines as being usable. A subsequent request will fail though,
which is an inconsistent behaviour from a userspace perspective.
Instead, let's check for the validity of the line and report it
as used if it is invalid. This allows a tool such as gpioinfo
to report something sensible:
gpiochip3 - 4 lines:
line 0: unnamed unused input active-high
line 1: unnamed kernel input active-high [used]
line 2: unnamed kernel input active-high [used]
line 3: unnamed unused input active-high
In this example, lines 1 and 2 are invalid, and cannot be used by
userspace.
Signed-off-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20201204164739.781812-2-maz@kernel.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib-cdev.c b/drivers/gpio/gpiolib-cdev.c
index f64a357..bd40d71 100644
--- a/drivers/gpio/gpiolib-cdev.c
+++ b/drivers/gpio/gpiolib-cdev.c
@@ -1914,6 +1914,7 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
test_bit(FLAG_EXPORT, &desc->flags) ||
test_bit(FLAG_SYSFS, &desc->flags) ||
+ !gpiochip_line_is_valid(gc, info->offset) ||
!ok_for_pinctrl)
info->flags |= GPIO_V2_LINE_FLAG_USED;