usb: gadget: f_fs: Document eventfd effect on descriptor format.
When FUNCTIONFS_EVENTFD flag is set, __ffs_data_got_descs reads a 32bits,
little-endian value right after the fixed structure header, and passes it
to eventfd_ctx_fdget. Document this.
Also, rephrase a comment to be affirmative about the role of string
descriptor at index 0. Ref: USB 2.0 spec paragraph "9.6.7 String", and
also checked to still be current in USB 3.0 spec paragraph "9.6.9 String".
Signed-off-by: Vincent Pelletier <plr.vincent@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c
index aab3fc1..818f499 100644
--- a/drivers/usb/gadget/function/f_fs.c
+++ b/drivers/usb/gadget/function/f_fs.c
@@ -2091,8 +2091,8 @@
case FFS_STRING:
/*
- * Strings are indexed from 1 (0 is magic ;) reserved
- * for languages list or some such)
+ * Strings are indexed from 1 (0 is reserved
+ * for languages list)
*/
if (*valuep > helper->ffs->strings_count)
helper->ffs->strings_count = *valuep;
diff --git a/include/uapi/linux/usb/functionfs.h b/include/uapi/linux/usb/functionfs.h
index acc6369..b2a31a5 100644
--- a/include/uapi/linux/usb/functionfs.h
+++ b/include/uapi/linux/usb/functionfs.h
@@ -93,6 +93,7 @@
* | 0 | magic | LE32 | FUNCTIONFS_DESCRIPTORS_MAGIC_V2 |
* | 4 | length | LE32 | length of the whole data chunk |
* | 8 | flags | LE32 | combination of functionfs_flags |
+ * | | eventfd | LE32 | eventfd file descriptor |
* | | fs_count | LE32 | number of full-speed descriptors |
* | | hs_count | LE32 | number of high-speed descriptors |
* | | ss_count | LE32 | number of super-speed descriptors |