On 09/10/2013 03:37 PM, Mark Brown wrote:
> On Tue, Sep 10, 2013 at 01:53:47PM -0600, Stephen Warren wrote:
>
>> Doesn't this patch call gpio_request() on the GPIO first, and
>> hence prevent the driver's own gpio_request() from succeeding,
>> since the GPIO is already requested? If this is not a problem, it
>> sounds like a bug in gpio_request() not ensuring mutual exclusion
>> for the GPIO.
>
> Or at the very least something that's likely to break in the
> future.
Looking at the GPIO code, it already prevents double-requests:
> if (test_and_set_bit(FLAG_REQUESTED, &desc->flags) == 0) {
> desc_set_label(desc, label ? : "?");
> status = 0;
> } else {
> status = -EBUSY;
> module_put(chip->owner);
> goto done;
> }
And I tested it in practice, and it really does fail.
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