dt-bindings: gpio: alignment with kernel v5.3

[oweals/u-boot.git] / doc / README.gpio

diff --git a/doc/README.gpio b/doc/README.gpio
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+++ b/doc/README.gpio
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+
+GPIO hog (CONFIG_GPIO_HOG)
+--------
+
+All the GPIO hog are initialized in gpio_hog_probe_all() function called in
+board_r.c just before board_late_init() but you can also acces directly to
+the gpio with gpio_hog_lookup_name().
+
+
+Example, for the device tree:
+
+        tca6416@20 {
+                compatible = "ti,tca6416";
+                reg = <0x20>;
+                #gpio-cells = <2>;
+                gpio-controller;
+
+                env_reset {
+                        gpio-hog;
+                        input;
+                        gpios = <6 GPIO_ACTIVE_LOW>;
+                };
+                boot_rescue {
+                        gpio-hog;
+                        input;
+                        line-name = "foo-bar-gpio";
+                        gpios = <7 GPIO_ACTIVE_LOW>;
+                };
+        };
+
+You can than access the gpio in your board code with:
+
+       struct gpio_desc *desc;
+       int ret;
+
+       ret = gpio_hog_lookup_name("boot_rescue", &desc);
+       if (ret)
+               return;
+       if (dm_gpio_get_value(desc) == 1)
+               printf("\nBooting into Rescue System\n");
+       else if (dm_gpio_get_value(desc) == 0)
+               printf("\nBoot normal\n");