gpiolib: safer implementation of desc_to_gpio()
gpiolib: safer implementation of desc_to_gpio()

The current implementation of desc_to_gpio() relies on the chip pointer
to be set to a valid value in order to compute the GPIO number. This
was done in the hope that we can get rid of the gpio_desc global array,
but this is not happening anytime soon.

This patch reimplements desc_to_gpio() in a fashion similar to that of
gpio_to_desc(). As a result, desc_to_gpio(gpio_to_desc(gpio)) == gpio is
now always true. This allows to call desc_to_gpio() on non-initialized
descriptors as some error-handling code currently does.

Signed-off-by: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@nvidia.com>
Reported-by: Dr. H. Nikolaus Schaller <f21c634a73790683e5c9fae328bcce65a30b7426@goldelico.com>
Signed-off-by: Linus Walleij <9cd9d802d23c0ed5e224beabf4ae4a5c478746ef@linaro.org>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs