[U-Boot] What can cause gpio_request return negative value

Nemanja Savic vlasinac at gmail.com
Thu Aug 15 14:18:04 UTC 2019

And to be more precise inside gpio-uclass.c, the function gpio_to_device
which is called by gpio_request loops through all gpio objects in order to
search for the gpio number provided never loops in my case.

for (ret = uclass_first_device(UCLASS_GPIO, &dev); dev; ret =
uclass_next_device(&dev)) {
puts("gpio-uclass loop\n");

puts inside loop is never executed, that's why I asked if I should maybe
first declare GPIOs to the system via device tree.

On Thu, Aug 15, 2019 at 4:05 PM Nemanja Savic <vlasinac at gmail.com> wrote:

> It return -2 which should be -ENOENT. In the comment at the end of
> gpio_to_device() it is written "No such GPIO".
> Are there any prerequisites before calling gpio_request regarding device
> tree or something else?
> On Thu, Aug 15, 2019 at 3:09 PM Adam Ford <aford173 at gmail.com> wrote:
>> On Thu, Aug 15, 2019 at 7:46 AM Nemanja Savic <vlasinac at gmail.com> wrote:
>> >
>> > Hi all,
>> >
>> > I am struggling with porting our old board init code for a sabre auto
>> based
>> > custom board with i.MX6 DualLite processor. The code used to work in our
>> > older u-boot version, but what I saw in mx6qsabreauto.c is that the new
>> > style is by using new driver model which means the gpio should be first
>> > requested. However gpio_request returns negative value in my case. Where
>> > could the problem be? As far as I could see our device tree doesn't
>> reserve
>> > this pin for other purpose. It is even not mentioned there. The only
>> thing
>> > related to those pins are iomux pin definitions in the device tree but
>> > removing that doesn't help at all. Also device tree for the Sabre Auto
>> > board doesn't mention gpio pins that they use in their u-boot. I am
>> dealing
>> > with 2017.03 version of u-boot.
>> Do you know what the negative value is?  include/linux/errno.h  should
>> have a list of error numbers which should correlate to the error
>> you're seeing.  That should also tell you what the error means.  From
>> there, you should be able to search the code for where that error
>> might return.
>> adam
>> > _______________________________________________
>> > U-Boot mailing list
>> > U-Boot at lists.denx.de
>> > https://lists.denx.de/listinfo/u-boot
> --
> Nemanja Savić

Nemanja Savić

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