usb: gadget: f_fs: Add flags to descriptors block

This reworks the way SuperSpeed descriptors are added and instead of
having a magic after full and high speed descriptors, it reworks the
whole descriptors block to include a flags field which lists which
descriptors are present and makes future extensions possible.

Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

1 files changed, 30 insertions, 19 deletions

diff --git a/include/uapi/linux/usb/functionfs.h b/include/uapi/linux/usb/functionfs.h
index 0f8f7be5b0d3..2a4b4a72a4f9 100644
--- a/include/uapi/linux/usb/functionfs.h
+++ b/include/uapi/linux/usb/functionfs.h
@@ -10,10 +10,15 @@
 
 enum {
 	FUNCTIONFS_DESCRIPTORS_MAGIC = 1,
-	FUNCTIONFS_STRINGS_MAGIC     = 2
+	FUNCTIONFS_STRINGS_MAGIC = 2,
+	FUNCTIONFS_DESCRIPTORS_MAGIC_V2 = 3,
 };
 
-#define FUNCTIONFS_SS_DESC_MAGIC 0x0055DE5C
+enum functionfs_flags {
+	FUNCTIONFS_HAS_FS_DESC = 1,
+	FUNCTIONFS_HAS_HS_DESC = 2,
+	FUNCTIONFS_HAS_SS_DESC = 4,
+};
 
 #ifndef __KERNEL__
 
@@ -30,33 +35,39 @@ struct usb_endpoint_descriptor_no_audio {
 
 
 /*
- * All numbers must be in little endian order.
- */
-
-struct usb_functionfs_descs_head {
-	__le32 magic;
-	__le32 length;
-	__le32 fs_count;
-	__le32 hs_count;
-} __attribute__((packed));
-
-/*
  * Descriptors format:
  *
  * | off | name      | type         | description                          |
  * |-----+-----------+--------------+--------------------------------------|
- * |   0 | magic     | LE32         | FUNCTIONFS_{FS,HS}_DESCRIPTORS_MAGIC |
+ * |   0 | magic     | LE32         | FUNCTIONFS_DESCRIPTORS_MAGIC_V2      |
+ * |   4 | length    | LE32         | length of the whole data chunk       |
+ * |   8 | flags     | LE32         | combination of functionfs_flags      |
+ * |     | fs_count  | LE32         | number of full-speed descriptors     |
+ * |     | hs_count  | LE32         | number of high-speed descriptors     |
+ * |     | ss_count  | LE32         | number of super-speed descriptors    |
+ * |     | fs_descrs | Descriptor[] | list of full-speed descriptors       |
+ * |     | hs_descrs | Descriptor[] | list of high-speed descriptors       |
+ * |     | ss_descrs | Descriptor[] | list of super-speed descriptors      |
+ *
+ * Depending on which flags are set, various fields may be missing in the
+ * structure.  Any flags that are not recognised cause the whole block to be
+ * rejected with -ENOSYS.
+ *
+ * Legacy descriptors format:
+ *
+ * | off | name      | type         | description                          |
+ * |-----+-----------+--------------+--------------------------------------|
+ * |   0 | magic     | LE32         | FUNCTIONFS_DESCRIPTORS_MAGIC         |
  * |   4 | length    | LE32         | length of the whole data chunk       |
  * |   8 | fs_count  | LE32         | number of full-speed descriptors     |
  * |  12 | hs_count  | LE32         | number of high-speed descriptors     |
  * |  16 | fs_descrs | Descriptor[] | list of full-speed descriptors       |
  * |     | hs_descrs | Descriptor[] | list of high-speed descriptors       |
- * |     | ss_magic  | LE32         | FUNCTIONFS_SS_DESC_MAGIC             |
- * |     | ss_count  | LE32         | number of super-speed descriptors    |
- * |     | ss_descrs | Descriptor[] | list of super-speed descriptors      |
  *
- * ss_magic: if present then it implies that SS_DESCs are also present
- * descs are just valid USB descriptors and have the following format:
+ * All numbers must be in little endian order.
+ *
+ * Descriptor[] is an array of valid USB descriptors which have the following
+ * format:
  *
  * | off | name            | type | description              |
  * |-----+-----------------+------+--------------------------|