dfu: add 'SKIP' entity

Define a new 'SKIP' type for the DFU entities. The flashed data for that
entity is simply ignored without returning any error values.

This allows to have one flashing procedure and images for the different
board types or variants, where each board uses only the images relevant
to it and skips the rest. This is especially usefull for the THOR
protocol, which usually transfers more than one file in a single session.

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Minkyu Kang <mk7.kang@samsung.com>
[mszyprow: rephrased commit message and docs for easier reading, changed
	   subject to "dfu: add 'SKIP' entity"]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>

doc/README.dfu

@@ -17,7 +17,7 @@ Overview:
   - The access to mediums is done in DFU backends (driver/dfu)
 
   Today the supported DFU backends are:
-  - MMC (RAW or FAT / EXT2 / EXT3 / EXT4 file system)
+  - MMC (RAW or FAT / EXT2 / EXT3 / EXT4 file system / SKIP)
   - NAND
   - RAM
   - SF (serial flash)
@@ -91,6 +91,7 @@ Commands:
       <name> part <dev> <part_id> [mmcpart <num>]  raw access to partition
       <name> fat <dev> <part_id> [mmcpart <num>]   file in FAT partition
       <name> ext4 <dev> <part_id> [mmcpart <num>]  file in EXT4 partition
+      <name> skip 0 0                              ignore flashed data
 
       with <partid> being the GPT or DOS partition index,
       with <num> being the eMMC hardware partition number.
@@ -103,6 +104,18 @@ Commands:
 
       "u-boot raw 0x80 0x800;uImage ext4 0 2"
 
+    If don't want to flash given image file to storage, use "skip" type
+    entity.
+    - It can be used to protect flashing wrong image for the specific board.
+    - Especailly, this layout will be useful when thor protocol is used,
+      which performs flashing in batch mode, where more than one file is
+      processed.
+    For example, if one makes a single tar file with support for the two
+    boards with u-boot-<board1>.bin and u-boot-<board2>.bin files, one
+    can use it to flash a proper u-boot image on both without a failure:
+
+      "u-boot-<board1>.bin raw 0x80 0x800; u-boot-<board2>.bin skip 0 0"
+
   "nand" (raw slc nand device)
     cmd: dfu 0 nand <dev>
     each element in "dfu_alt_info" =

drivers/dfu/dfu.c

@@ -614,7 +614,7 @@ const char *dfu_get_dev_type(enum dfu_device_type t)
 const char *dfu_get_layout(enum dfu_layout l)
 {
 	const char *const dfu_layout[] = {NULL, "RAW_ADDR", "FAT", "EXT2",
-					  "EXT3", "EXT4", "RAM_ADDR" };
+					  "EXT3", "EXT4", "RAM_ADDR", "SKIP" };
 	return dfu_layout[l];
 }
 

drivers/dfu/dfu_mmc.c

@@ -108,6 +108,8 @@ static int mmc_file_op(enum dfu_op op, struct dfu_entity *dfu,
 	case DFU_FS_EXT4:
 		fstype = FS_TYPE_EXT;
 		break;
+	case DFU_SKIP:
+		return 0;
 	default:
 		printf("%s: Layout (%s) not (yet) supported!\n", __func__,
 		       dfu_get_layout(dfu->layout));
@@ -204,6 +206,9 @@ int dfu_write_medium_mmc(struct dfu_entity *dfu,
 	case DFU_FS_EXT4:
 		ret = mmc_file_buf_write(dfu, offset, buf, len);
 		break;
+	case DFU_SKIP:
+		ret = 0;
+		break;
 	default:
 		printf("%s: Layout (%s) not (yet) supported!\n", __func__,
 		       dfu_get_layout(dfu->layout));
@@ -238,6 +243,8 @@ int dfu_get_medium_size_mmc(struct dfu_entity *dfu, u64 *size)
 		if (ret < 0)
 			return ret;
 		return 0;
+	case DFU_SKIP:
+		return 0;
 	default:
 		printf("%s: Layout (%s) not (yet) supported!\n", __func__,
 		       dfu_get_layout(dfu->layout));
@@ -399,6 +406,8 @@ int dfu_fill_entity_mmc(struct dfu_entity *dfu, char *devstr, char *s)
 		dfu->layout = DFU_FS_FAT;
 	} else if (!strcmp(entity_type, "ext4")) {
 		dfu->layout = DFU_FS_EXT4;
+	} else if (!strcmp(entity_type, "skip")) {
+		dfu->layout = DFU_SKIP;
 	} else {
 		pr_err("Memory layout (%s) not supported!\n", entity_type);
 		return -ENODEV;

include/dfu.h

@@ -33,6 +33,7 @@ enum dfu_layout {
 	DFU_FS_EXT3,
 	DFU_FS_EXT4,
 	DFU_RAM_ADDR,
+	DFU_SKIP,
 };
 
 enum dfu_op {