drivers/disp_dev: add display driver registry

drivers/disp_dev/disp_dev.c

@@ -21,9 +21,46 @@
 #include <assert.h>
 #include <stdbool.h>
 #include <inttypes.h>
+#include <errno.h>
 
 #include "disp_dev.h"
 
+disp_dev_reg_t *disp_dev_reg = NULL;
+
+int disp_dev_reg_add(disp_dev_reg_t *dev)
+{
+    disp_dev_reg_t *tmp = disp_dev_reg;
+
+    if (dev == NULL) {
+        return -ENODEV;
+    }
+
+    /* prepare new entry */
+    dev->next = NULL;
+    /* add to registry */
+    if (disp_dev_reg == NULL) {
+        disp_dev_reg = dev;
+    }
+    else {
+        while (tmp->next != NULL) {
+            tmp = tmp->next;
+        }
+        tmp->next = dev;
+    }
+    return 0;
+}
+
+disp_dev_reg_t *disp_dev_reg_find_screen(uint8_t screen_id)
+{
+    disp_dev_reg_t *tmp = disp_dev_reg;
+
+    while (tmp && tmp->screen_id != screen_id) {
+        tmp = tmp->next;
+    }
+
+    return tmp;
+}
+
 void disp_dev_map(const disp_dev_t *dev,
                   uint16_t x1, uint16_t x2, uint16_t y1, uint16_t y2,
                   const uint16_t *color)

drivers/include/disp_dev.h

@@ -101,6 +101,40 @@ struct disp_dev {
     const disp_dev_driver_t *driver;    /**< Pointer to driver of the display device */
 };
 
+/**
+ * @brief   Disp dev registry entry
+ */
+typedef struct disp_dev_reg {
+    struct disp_dev_reg *next;      /**< pointer to the next display device in the list */
+    disp_dev_t *dev;                /**< pointer to the device descriptor */
+    uint8_t screen_id;              /**< id of the screen this display is attached to */
+} disp_dev_reg_t;
+
+/**
+ * @brief   Export the display device registry as global variable
+ */
+extern disp_dev_reg_t *disp_dev_reg;
+
+/**
+ * @brief   Add pointer to a display device item to the list of display items
+ *
+ * @param[in] dev   Pointer to the display device
+ *
+ * @return          0 on success
+ * @return         -ENODEV on invalid entry
+*/
+int disp_dev_reg_add(disp_dev_reg_t *dev);
+
+/**
+ * @brief   Find the display device that is attached to a given screen
+ *
+ * @param[in] screen_id Identifier (number) of the screen
+ *
+ * @return              pointer to the display device in the registry
+ * @return              NULL if there's no match
+*/
+disp_dev_reg_t *disp_dev_reg_find_screen(uint8_t screen_id);
+
 /**
  * @brief   Map an area to display on the device
  *