Hi,
On 11/08/2017 04:37 AM, Timur Tabi wrote:
Add support for specifying that some GPIOs within a range are unavailable.
Some systems have a sparse list of GPIOs, where a range of GPIOs is
specified (usually 0 to n-1), but some subset within that range is
absent or unavailable for whatever reason.
To support this, allow drivers to specify a bitmask of GPIOs that
are present or absent. Gpiolib will then block access to those that
are absent.
Signed-off-by: Timur Tabi <timur@xxxxxxxxxxxxxx>
---
drivers/gpio/gpiolib.c | 43 +++++++++++++++++++++++++++++++++++--------
include/linux/gpio/driver.h | 2 ++
2 files changed, 37 insertions(+), 8 deletions(-)
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 60553af4c004..c32387936cdd 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1481,22 +1481,36 @@ static struct gpio_chip *find_chip_by_name(const char *name)
static int gpiochip_irqchip_init_valid_mask(struct gpio_chip *gpiochip)
{
- if (!gpiochip->irq_need_valid_mask)
- return 0;
+ if (gpiochip->irq_need_valid_mask) {
+ gpiochip->irq_valid_mask =
+ kcalloc(BITS_TO_LONGS(gpiochip->ngpio),
+ sizeof(long), GFP_KERNEL);
+ if (!gpiochip->irq_valid_mask)
+ return -ENOMEM;
- gpiochip->irq_valid_mask = kcalloc(BITS_TO_LONGS(gpiochip->ngpio),
- sizeof(long), GFP_KERNEL);
- if (!gpiochip->irq_valid_mask)
- return -ENOMEM;
+ /* Assume by default all GPIOs are valid */
+ bitmap_fill(gpiochip->irq_valid_mask, gpiochip->ngpio);
+ }
- /* Assume by default all GPIOs are valid */
- bitmap_fill(gpiochip->irq_valid_mask, gpiochip->ngpio);
+ if (gpiochip->line_need_valid_mask) {
+ gpiochip->line_valid_mask =
+ kcalloc(BITS_TO_LONGS(gpiochip->ngpio),
+ sizeof(long), GFP_KERNEL);
+ if (!gpiochip->line_valid_mask)
+ return -ENOMEM;
+
+ /* Assume by default all GPIOs are valid */
+ bitmap_fill(gpiochip->line_valid_mask, gpiochip->ngpio);
+ }
return 0;
}
static void gpiochip_irqchip_free_valid_mask(struct gpio_chip *gpiochip)
{
+ kfree(gpiochip->line_valid_mask);
+ gpiochip->line_valid_mask = NULL;
+
kfree(gpiochip->irq_valid_mask);
gpiochip->irq_valid_mask = NULL;
}
@@ -1510,6 +1524,15 @@ static bool gpiochip_irqchip_irq_valid(const struct gpio_chip *gpiochip,
return test_bit(offset, gpiochip->irq_valid_mask);
}
+static bool gpiochip_irqchip_line_valid(const struct gpio_chip *gpiochip,
+ unsigned int offset)
+{
+ /* No mask means all valid */
+ if (likely(!gpiochip->line_valid_mask))
+ return true;
+ return test_bit(offset, gpiochip->line_valid_mask);
+}
+
/**
* gpiochip_set_cascaded_irqchip() - connects a cascaded irqchip to a gpiochip
* @gpiochip: the gpiochip to set the irqchip chain to
@@ -3320,6 +3343,10 @@ struct gpio_desc *__must_check gpiod_get_index(struct device *dev,
return desc;
}
+ /* Make sure the GPIO is valid before we request it. */
+ if (!gpiochip_irqchip_line_valid(desc->gdev->chip, idx))
+ return ERR_PTR(-EACCES);
We're hitting an issue here ^ when a consumer calls the devm_gpiod_get() API. This API
internally sets idx in gpiod_get_index to always 0. For example, in the call sequence
below, the idx argument to gpiochip_irqchip_line_valid is always 0:
devm_gpiod_get(dev, con_id, flags)
devm_gpiod_get_index(dev, con_id, 0, flags)
gpiod_get_index(dev, con_id, 0, flags)
if (!gpiochip_irqchip_line_valid(desc->gdev->chip, 0))
return ERR_PTR(-EACCES);
Therefore, with these patches, if we create a sparse gpio map, and the
0th gpio is set to "not accessible", all gpio requests end up failing with EACCESS
because idx is always passed as 0.
In gpiochip_irqchip_line_valid, shouldn't we test the nth bit (that corresponds to
this gpio_desc) in chip->line_valid_mask instead of idx passed above, which is always
0?
Thanks,
Archit
+
status = gpiod_request(desc, con_id);
if (status < 0)
return ERR_PTR(status);
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 424e5139ff10..853828ccabc8 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -173,6 +173,8 @@ struct gpio_chip {
bool irq_nested;
bool irq_need_valid_mask;
unsigned long *irq_valid_mask;
+ bool line_need_valid_mask;
+ unsigned long *line_valid_mask;
struct lock_class_key *lock_key;
#endif
--
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