[U-Boot] [RFC, PATCH v4 05/16] env: fat: add U-Boot environment context support

[AKASHI Takahiro]

Please note that the aim of this patch is to illustrate how we can
extend the existing backing storage drivers for env interfaces to
support U-Boot environment context.

We will be able to support more devices as well as more contexts
in a similar way. Existing drivers still work exactly in the same
way as before while they are not extended yet.

Signed-off-by: AKASHI Takahiro <takahiro.akashi at linaro.org>
---
 env/fat.c | 103 ++++++++++++++++++++++++++++++++++++++++++++----------
 1 file changed, 84 insertions(+), 19 deletions(-)

diff --git a/env/fat.c b/env/fat.c
index 7f74c64dfe7e..e4a672d2730a 100644
--- a/env/fat.c
+++ b/env/fat.c
@@ -30,23 +30,44 @@
 # endif
 #endif
 
+static struct evn_fat_context {
+	char *interface;
+	char *dev_and_part;
+	char *file;
+} fat_context[ENVCTX_COUNT] = {
+#if defined(CONFIG_ENV_FAT_INTERFACE) && \
+	defined(CONFIG_ENV_FAT_DEVICE_AND_PART) && defined(CONFIG_ENV_FAT_FILE)
+	[ENVCTX_UBOOT] = {
+		CONFIG_ENV_FAT_INTERFACE,
+		CONFIG_ENV_FAT_DEVICE_AND_PART,
+		CONFIG_ENV_FAT_FILE,
+	},
+#endif
+};
+
 #ifdef CMD_SAVEENV
-static int env_fat_save(void)
+static int env_fat_save_ext(enum env_context ctx)
 {
 	env_t __aligned(ARCH_DMA_MINALIGN) env_new;
+	env_hdr_t *envp;
 	struct blk_desc *dev_desc = NULL;
 	disk_partition_t info;
 	int dev, part;
 	int err;
 	loff_t size;
 
-	err = env_export(&env_new);
+	if (!fat_context[ctx].interface)
+		return -EIO;
+
+	env_new.data_size = ENV_SIZE;
+	envp = (env_hdr_t *)&env_new;
+	err = env_export_ext(&envp, ctx);
 	if (err)
 		return err;
 
-	part = blk_get_device_part_str(CONFIG_ENV_FAT_INTERFACE,
-					CONFIG_ENV_FAT_DEVICE_AND_PART,
-					&dev_desc, &info, 1);
+	part = blk_get_device_part_str(fat_context[ctx].interface,
+				       fat_context[ctx].dev_and_part,
+				       &dev_desc, &info, 1);
 	if (part < 0)
 		return 1;
 
@@ -57,28 +78,34 @@ static int env_fat_save(void)
 		 * will calling it. The missing \n is intentional.
 		 */
 		printf("Unable to use %s %d:%d... ",
-		       CONFIG_ENV_FAT_INTERFACE, dev, part);
+		       fat_context[ctx].interface, dev, part);
 		return 1;
 	}
 
-	err = file_fat_write(CONFIG_ENV_FAT_FILE, (void *)&env_new, 0, sizeof(env_t),
-			     &size);
+	err = file_fat_write(fat_context[ctx].file, (void *)envp, 0,
+			     sizeof(env_hdr_t) + envp->data_size, &size);
 	if (err == -1) {
 		/*
 		 * This printf is embedded in the messages from env_save that
 		 * will calling it. The missing \n is intentional.
 		 */
 		printf("Unable to write \"%s\" from %s%d:%d... ",
-			CONFIG_ENV_FAT_FILE, CONFIG_ENV_FAT_INTERFACE, dev, part);
+		       fat_context[ctx].file, fat_context[ctx].interface,
+		       dev, part);
 		return 1;
 	}
 
 	return 0;
 }
+
+static int env_fat_save(void)
+{
+	return env_fat_save_ext(ENVCTX_UBOOT);
+}
 #endif /* CMD_SAVEENV */
 
 #ifdef LOADENV
-static int env_fat_load(void)
+static int env_fat_load_ext(enum env_context ctx)
 {
 	ALLOC_CACHE_ALIGN_BUFFER(char, buf, CONFIG_ENV_SIZE);
 	struct blk_desc *dev_desc = NULL;
@@ -86,14 +113,17 @@ static int env_fat_load(void)
 	int dev, part;
 	int err;
 
+	if (!fat_context[ctx].interface)
+		return -EIO;
+
 #ifdef CONFIG_MMC
-	if (!strcmp(CONFIG_ENV_FAT_INTERFACE, "mmc"))
+	if (!strcmp(fat_context[ctx].interface, "mmc"))
 		mmc_initialize(NULL);
 #endif
 
-	part = blk_get_device_part_str(CONFIG_ENV_FAT_INTERFACE,
-					CONFIG_ENV_FAT_DEVICE_AND_PART,
-					&dev_desc, &info, 1);
+	part = blk_get_device_part_str(fat_context[ctx].interface,
+				       fat_context[ctx].dev_and_part,
+				       &dev_desc, &info, 1);
 	if (part < 0)
 		goto err_env_relocate;
 
@@ -104,37 +134,72 @@ static int env_fat_load(void)
 		 * will calling it. The missing \n is intentional.
 		 */
 		printf("Unable to use %s %d:%d... ",
-		       CONFIG_ENV_FAT_INTERFACE, dev, part);
+		       fat_context[ctx].interface, dev, part);
 		goto err_env_relocate;
 	}
 
-	err = file_fat_read(CONFIG_ENV_FAT_FILE, buf, CONFIG_ENV_SIZE);
+	err = file_fat_read(fat_context[ctx].file, buf, CONFIG_ENV_SIZE);
 	if (err == -1) {
 		/*
 		 * This printf is embedded in the messages from env_save that
 		 * will calling it. The missing \n is intentional.
 		 */
 		printf("Unable to read \"%s\" from %s%d:%d... ",
-			CONFIG_ENV_FAT_FILE, CONFIG_ENV_FAT_INTERFACE, dev, part);
+		       fat_context[ctx].file, fat_context[ctx].interface,
+		       dev, part);
 		goto err_env_relocate;
 	}
 
-	return env_import(buf, 1);
+	if (((env_hdr_t *)buf)->data_size <= 1)
+		return 0;
+
+	return env_import_ext(buf, ctx, 1);
 
 err_env_relocate:
-	set_default_env(NULL, 0);
+	if (ctx == ENVCTX_UBOOT)
+		set_default_env(NULL, 0);
 
 	return -EIO;
 }
+
+static int env_fat_load(void)
+{
+	return env_fat_load_ext(ENVCTX_UBOOT);
+}
 #endif /* LOADENV */
 
+#if defined(CMD_LOADENV) || defined(CMD_SAVEENV)
+static int env_fat_init_ext(enum env_context ctx)
+{
+	if (ctx != ENVCTX_UBOOT)
+		return 0;
+	/*
+	 * Note:
+	 * We can't report 0 here because low-level storage driver,
+	 * like scsi, may not have been detected yet at boot time.
+	 */
+	return -ENOENT;
+}
+
+static int env_fat_init(void)
+{
+	return env_fat_init_ext(ENVCTX_UBOOT);
+}
+#endif
+
 U_BOOT_ENV_LOCATION(fat) = {
 	.location	= ENVL_FAT,
 	ENV_NAME("FAT")
 #ifdef LOADENV
 	.load		= env_fat_load,
+	.load_ext	= env_fat_load_ext,
 #endif
 #ifdef CMD_SAVEENV
 	.save		= env_save_ptr(env_fat_save),
+	.save_ext	= env_save_ptr(env_fat_save_ext),
+#endif
+#if defined(CMD_LOADENV) || defined(CMD_SAVEENV)
+	.init		= env_fat_init,
+	.init_ext	= env_fat_init_ext,
 #endif
 };
-- 
2.21.0