gui: Added glue logic for LittlevGL GUI library

Added glue logic to interface Zephyr with LittlevGL GUI library

This includes:
 * KConfig options for all lvgl options
 * Kernel & user space memory management
 * Zephyr to lvgl FS call mapping
 * Color space conversion function

Signed-off-by: Jan Van Winkel <jan.van_winkel@dxplore.eu>

lib/gui/lvgl/lvgl_fs.c

@@ -0,0 +1,243 @@
+/*
+ * Copyright (c) 2018 Jan Van Winkel <jan.van_winkel@dxplore.eu>
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <lvgl.h>
+#include <zephyr.h>
+#include <fs.h>
+
+/* Stub for LVGL ufs (ram based FS) init function
+ * as we use Zephyr FS API instead
+ */
+void lv_ufs_init(void)
+{
+}
+
+bool lvgl_fs_ready(void)
+{
+	return true;
+}
+
+static lv_fs_res_t errno_to_lv_fs_res(int err)
+{
+	switch (err) {
+	case 0:
+		return LV_FS_RES_OK;
+	case -EIO:
+		/*Low level hardware error*/
+		return LV_FS_RES_HW_ERR;
+	case -EBADF:
+		/*Error in the file system structure */
+		return LV_FS_RES_FS_ERR;
+	case -ENOENT:
+		/*Driver, file or directory is not exists*/
+		return LV_FS_RES_NOT_EX;
+	case -EFBIG:
+		/*Disk full*/
+		return LV_FS_RES_FULL;
+	case -EACCES:
+		/*Access denied. Check 'fs_open' modes and write protect*/
+		return LV_FS_RES_DENIED;
+	case -EBUSY:
+		/*The file system now can't handle it, try later*/
+		return LV_FS_RES_BUSY;
+	case -ENOMEM:
+		/*Not enough memory for an internal operation*/
+		return LV_FS_RES_OUT_OF_MEM;
+	case -EINVAL:
+		/*Invalid parameter among arguments*/
+		return LV_FS_RES_INV_PARAM;
+	default:
+		return LV_FS_RES_UNKNOWN;
+	}
+}
+
+static lv_fs_res_t lvgl_fs_open(void *file, const char *path,
+		lv_fs_mode_t mode)
+{
+	int err;
+
+	err = fs_open((struct fs_file_t *)file, path);
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_close(void *file)
+{
+	int err;
+
+	err = fs_close((struct fs_file_t *)file);
+	return LV_FS_RES_NOT_IMP;
+}
+
+static lv_fs_res_t lvgl_fs_remove(const char *path)
+{
+	int err;
+
+	err = fs_unlink(path);
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_read(void *file, void *buf, u32_t btr,
+		u32_t *br)
+{
+	int err;
+
+	err = fs_read((struct fs_file_t *)file, buf, btr);
+	if (err > 0) {
+		if (br != NULL) {
+			*br = err;
+		}
+		err = 0;
+	} else if (br != NULL) {
+		*br = 0;
+	}
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_write(void *file, const void *buf, u32_t btw,
+		u32_t *bw)
+{
+	int err;
+
+	err = fs_write((struct fs_file_t *)file, buf, btw);
+	if (err == btw) {
+		if (bw != NULL) {
+			*bw = btw;
+		}
+		err = 0;
+	} else if (err < 0) {
+		if (bw != NULL) {
+			*bw = 0;
+		}
+	} else {
+		if (bw != NULL) {
+			*bw = err;
+		}
+		err = -EFBIG;
+	}
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_seek(void *file, u32_t pos)
+{
+	int err;
+
+	err = fs_seek((struct fs_file_t *)file, pos, FS_SEEK_SET);
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_tell(void *file, u32_t *pos_p)
+{
+	*pos_p = fs_tell((struct fs_file_t *)file);
+	return LV_FS_RES_OK;
+}
+
+static lv_fs_res_t lvgl_fs_trunc(void *file)
+{
+	int err;
+	off_t length;
+
+	length = fs_tell((struct fs_file_t *) file);
+	++length;
+	err = fs_truncate((struct fs_file_t *)file, length);
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_size(void *file, u32_t *fsize)
+{
+	int err;
+	off_t org_pos;
+
+	/* LVGL does not provided path but pointer to file struct as such
+	 * we can not use fs_stat, instead use a combination of fs_tell and
+	 * fs_seek to get the files size.
+	 */
+
+	org_pos = fs_tell((struct fs_file_t *) file);
+
+	err = fs_seek((struct fs_file_t *) file, 0, FS_SEEK_END);
+	if (err != 0) {
+		*fsize = 0;
+		return errno_to_lv_fs_res(err);
+	}
+
+	*fsize = fs_tell((struct fs_file_t *) file) + 1;
+
+	err = fs_seek((struct fs_file_t *) file, org_pos, FS_SEEK_SET);
+
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_rename(const char *from, const char *to)
+{
+	int err;
+
+	err = fs_rename(from, to);
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_free(u32_t *total_p, u32_t *free_p)
+{
+	/* We have no easy way of telling the total file system size.
+	 * Zephyr can only return this information per mount point.
+	 */
+	return LV_FS_RES_NOT_IMP;
+}
+
+static lv_fs_res_t lvgl_fs_dir_open(void *dir, const char *path)
+{
+	int err;
+
+	err = fs_opendir((struct fs_dir_t *)dir, path);
+	return errno_to_lv_fs_res(err);
+}
+
+static lv_fs_res_t lvgl_fs_dir_read(void *dir, char *fn)
+{
+	/* LVGL expects a string as return parameter but the format of the
+	 * string is not documented.
+	 */
+	return LV_FS_RES_NOT_IMP;
+}
+
+static lv_fs_res_t lvgl_fs_dir_close(void *dir)
+{
+	int err;
+
+	err = fs_closedir((struct fs_dir_t *)dir);
+	return errno_to_lv_fs_res(err);
+}
+
+
+void lvgl_fs_init(void)
+{
+	lv_fs_drv_t fs_drv;
+
+	memset(&fs_drv, 0, sizeof(lv_fs_drv_t));
+
+	fs_drv.file_size = sizeof(struct fs_file_t);
+	fs_drv.rddir_size = sizeof(struct fs_dir_t);
+	fs_drv.letter = '/';
+	fs_drv.ready = lvgl_fs_ready;
+
+	fs_drv.open = lvgl_fs_open;
+	fs_drv.close = lvgl_fs_close;
+	fs_drv.remove = lvgl_fs_remove;
+	fs_drv.read = lvgl_fs_read;
+	fs_drv.write = lvgl_fs_write;
+	fs_drv.seek = lvgl_fs_seek;
+	fs_drv.tell = lvgl_fs_tell;
+	fs_drv.trunc = lvgl_fs_trunc;
+	fs_drv.size = lvgl_fs_size;
+	fs_drv.rename = lvgl_fs_rename;
+	fs_drv.free = lvgl_fs_free;
+
+	fs_drv.dir_open = lvgl_fs_dir_open;
+	fs_drv.dir_read = lvgl_fs_dir_read;
+	fs_drv.dir_close = lvgl_fs_dir_close;
+
+	lv_fs_add_drv(&fs_drv);
+}
+