image: Tidy up genimg_get_kernel_addr_fit()

This function does not modify its first argument, so mark it const. Also
move the comments to the header file and expand them to provide more
useful information.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>

boot/bootm.c

@@ -122,8 +122,7 @@ static const void *boot_get_kernel(struct cmd_tbl *cmdtp, int flag, int argc,
 #endif
 	ulong		img_addr;
 	const void *buf;
-	const char	*fit_uname_config = NULL;
-	const char	*fit_uname_kernel = NULL;
+	const char *fit_uname_config = NULL, *fit_uname_kernel = NULL;
 #if CONFIG_IS_ENABLED(FIT)
 	int		os_noffset;
 #endif

boot/image-board.c

@@ -198,22 +198,7 @@ void memmove_wd(void *to, void *from, size_t len, ulong chunksz)
 	}
 }
 
-/**
- * genimg_get_kernel_addr_fit - get the real kernel address and return 2
- *                              FIT strings
- * @img_addr: a string might contain real image address
- * @fit_uname_config: double pointer to a char, will hold pointer to a
- *                    configuration unit name
- * @fit_uname_kernel: double pointer to a char, will hold pointer to a subimage
- *                    name
- *
- * genimg_get_kernel_addr_fit get the real kernel start address from a string
- * which is normally the first argv of bootm/bootz
- *
- * returns:
- *     kernel start address
- */
-ulong genimg_get_kernel_addr_fit(char * const img_addr,
+ulong genimg_get_kernel_addr_fit(const char *const img_addr,
 				 const char **fit_uname_config,
 				 const char **fit_uname_kernel)
 {

include/image.h

@@ -612,9 +612,32 @@ int boot_get_setup(struct bootm_headers *images, uint8_t arch, ulong *setup_star
 #define IMAGE_FORMAT_FIT	0x02	/* new, libfdt based format */
 #define IMAGE_FORMAT_ANDROID	0x03	/* Android boot image */
 
-ulong genimg_get_kernel_addr_fit(char * const img_addr,
+/**
+ * genimg_get_kernel_addr_fit() - Parse FIT specifier
+ *
+ * Get the real kernel start address from a string which is normally the first
+ * argv of bootm/bootz
+ *
+ * These cases are dealt with, based on the value of @img_addr:
+ *    NULL: Returns image_load_addr, does not set last two args
+ *    "<addr>": Returns address
+ *
+ * For FIT:
+ *    "[<addr>]#<conf>": Returns address (or image_load_addr),
+ *	sets fit_uname_config to config name
+ *    "[<addr>]:<subimage>": Returns address (or image_load_addr) and sets
+ *	fit_uname_kernel to the subimage name
+ *
+ * @img_addr: a string might contain real image address (or NULL)
+ * @fit_uname_config: Returns configuration unit name
+ * @fit_uname_kernel: Returns subimage name
+ *
+ * Returns: kernel start address
+ */
+ulong genimg_get_kernel_addr_fit(const char *const img_addr,
 				 const char **fit_uname_config,
 				 const char **fit_uname_kernel);
+
 ulong genimg_get_kernel_addr(char * const img_addr);
 int genimg_get_format(const void *img_addr);
 int genimg_has_config(struct bootm_headers *images);