@@ -2390,74 +2390,72 @@ static void gpio_desc_to_lineinfo(struct gpio_desc *desc,
struct gpio_v2_line_info *info)
{
struct gpio_chip *gc = desc->gdev->chip;
- bool ok_for_pinctrl;
- unsigned long flags;
+ unsigned long dflags;
memset(info, 0, sizeof(*info));
info->offset = gpio_chip_hwgpio(desc);
- /*
- * This function takes a mutex so we must check this before taking
- * the spinlock.
- *
- * FIXME: find a non-racy way to retrieve this information. Maybe a
- * lock common to both frameworks?
- */
- ok_for_pinctrl = pinctrl_gpio_can_use_line(gc, info->offset);
+ scoped_guard(spinlock_irqsave, &gpio_lock) {
+ if (desc->name)
+ strscpy(info->name, desc->name, sizeof(info->name));
- spin_lock_irqsave(&gpio_lock, flags);
+ if (desc->label)
+ strscpy(info->consumer, desc->label,
+ sizeof(info->consumer));
- if (desc->name)
- strscpy(info->name, desc->name, sizeof(info->name));
-
- if (desc->label)
- strscpy(info->consumer, desc->label, sizeof(info->consumer));
+ dflags = READ_ONCE(desc->flags);
+ }
/*
- * Userspace only need to know that the kernel is using this GPIO so
- * it can't use it.
+ * Userspace only need know that the kernel is using this GPIO so it
+ * can't use it.
+ * The calculation of the used flag is slightly racy, as it may read
+ * desc, gc and pinctrl state without a lock covering all three at
+ * once. Worst case if the line is in transition and the calculation
+ * is inconsistent then it looks to the user like they performed the
+ * read on the other side of the transition - but that can always
+ * happen.
+ * The definitive test that a line is available to userspace is to
+ * request it.
*/
- info->flags = 0;
- if (test_bit(FLAG_REQUESTED, &desc->flags) ||
- test_bit(FLAG_IS_HOGGED, &desc->flags) ||
- test_bit(FLAG_USED_AS_IRQ, &desc->flags) ||
- test_bit(FLAG_EXPORT, &desc->flags) ||
- test_bit(FLAG_SYSFS, &desc->flags) ||
+ if (test_bit(FLAG_REQUESTED, &dflags) ||
+ test_bit(FLAG_IS_HOGGED, &dflags) ||
+ test_bit(FLAG_USED_AS_IRQ, &dflags) ||
+ test_bit(FLAG_EXPORT, &dflags) ||
+ test_bit(FLAG_SYSFS, &dflags) ||
!gpiochip_line_is_valid(gc, info->offset) ||
- !ok_for_pinctrl)
+ !pinctrl_gpio_can_use_line(gc, info->offset))
info->flags |= GPIO_V2_LINE_FLAG_USED;
- if (test_bit(FLAG_IS_OUT, &desc->flags))
+ if (test_bit(FLAG_IS_OUT, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_OUTPUT;
else
info->flags |= GPIO_V2_LINE_FLAG_INPUT;
- if (test_bit(FLAG_ACTIVE_LOW, &desc->flags))
+ if (test_bit(FLAG_ACTIVE_LOW, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_ACTIVE_LOW;
- if (test_bit(FLAG_OPEN_DRAIN, &desc->flags))
+ if (test_bit(FLAG_OPEN_DRAIN, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_OPEN_DRAIN;
- if (test_bit(FLAG_OPEN_SOURCE, &desc->flags))
+ if (test_bit(FLAG_OPEN_SOURCE, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_OPEN_SOURCE;
- if (test_bit(FLAG_BIAS_DISABLE, &desc->flags))
+ if (test_bit(FLAG_BIAS_DISABLE, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_BIAS_DISABLED;
- if (test_bit(FLAG_PULL_DOWN, &desc->flags))
+ if (test_bit(FLAG_PULL_DOWN, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_BIAS_PULL_DOWN;
- if (test_bit(FLAG_PULL_UP, &desc->flags))
+ if (test_bit(FLAG_PULL_UP, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_BIAS_PULL_UP;
- if (test_bit(FLAG_EDGE_RISING, &desc->flags))
+ if (test_bit(FLAG_EDGE_RISING, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_EDGE_RISING;
- if (test_bit(FLAG_EDGE_FALLING, &desc->flags))
+ if (test_bit(FLAG_EDGE_FALLING, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_EDGE_FALLING;
- if (test_bit(FLAG_EVENT_CLOCK_REALTIME, &desc->flags))
+ if (test_bit(FLAG_EVENT_CLOCK_REALTIME, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_REALTIME;
- else if (test_bit(FLAG_EVENT_CLOCK_HTE, &desc->flags))
+ else if (test_bit(FLAG_EVENT_CLOCK_HTE, &dflags))
info->flags |= GPIO_V2_LINE_FLAG_EVENT_CLOCK_HTE;
-
- spin_unlock_irqrestore(&gpio_lock, flags);
}
struct gpio_chardev_data {