gpio: chardev: Add helper to retrieve gpiochip and line offset by lin…

…e name

This makes the retrieval robust against chips being reordered during
boot. The results can be used to fill out mraa_pin_t while initializing
a board.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

include/gpio/gpio_chardev.h

@@ -49,6 +49,8 @@ mraa_boolean_t mraa_is_gpio_line_open_source(mraa_gpiod_line_info *linfo);
 int mraa_get_number_of_gpio_chips();
 int mraa_get_chip_infos(mraa_gpiod_chip_info*** cinfos);
 
+int mraa_find_gpio_line_by_name(const char *name, unsigned *chip_number, unsigned *line_number);
+
 /* Multiple gpio support. */
 typedef struct _gpio_group* mraa_gpiod_group_t;
 

src/gpio/gpio_chardev.c

@@ -444,3 +444,47 @@ mraa_get_chip_infos(mraa_gpiod_chip_info*** cinfos)
 
     return num_chips;
 }
+
+#ifndef GPIO_MAX_NAME_SIZE
+#define GPIO_MAX_NAME_SIZE 32
+#endif
+
+int
+mraa_find_gpio_line_by_name(const char *name, unsigned *chip_number, unsigned *line_number)
+{
+    mraa_gpiod_chip_info **cinfos;
+    mraa_gpiod_chip_info *cinfo;
+    mraa_gpiod_line_info *linfo;
+    int num_chips, i;
+
+    num_chips = mraa_get_chip_infos(&cinfos);
+    if (num_chips < 0) {
+        return -1;
+    }
+
+    for_each_gpio_chip(cinfo, cinfos, num_chips) {
+        for (i = 0; i < cinfo->chip_info.lines; i++) {
+            linfo = mraa_get_line_info_by_chip_name(cinfo->chip_info.name, i);
+
+            if (!strncmp(linfo->name, name, GPIO_MAX_NAME_SIZE)) {
+                if (chip_number) {
+                    /* idx is coming from `for_each_gpio_chip` definition */
+                    *chip_number = idx;
+                }
+
+                if (line_number) {
+                    *line_number = linfo->line_offset;
+                }
+
+                free(linfo);
+                free(cinfos);
+                return 0;
+            }
+
+            free(linfo);
+        }
+    }
+
+    free(cinfos);
+    return -1;
+}