On 12/01/2017 05:38 AM, Archit Taneja wrote:
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.
Ok, I can see the problem, but I don't know how to fix it.
struct gpio_desc *__must_check devm_gpiod_get(struct device *dev,
const char *con_id,
enum gpiod_flags flags)
{
return devm_gpiod_get_index(dev, con_id, 0, flags);
}
I thought that by putting the check for "availability" inside of the
GPIO request, it would handle all situations where a client (whether
kernel or user-space) tries to access a specific GPIO.
However, this doesn't work with [devm_]gpiod_get. This function
attempts to claim the entire GPIO block by claiming only the first GPIO.
This is straining my understanding of gpiolib. Maybe we need to do
something like this:
struct gpio_desc *__must_check gpiod_get(struct device *dev, const char
*con_id,
enum gpiod_flags flags)
{
return gpiod_get_index(dev, con_id, -1, flags);
}
Where idx == -1 is a special-case for gpiod_get_index() where it returns
the gpio_desc without actually requesting it?
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?
The code has changed upstream, so I need to refactor that function. But
I think it's already testing the nth bit:
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);
'offset' is the nth bit.
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