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Commit 96a420d2 authored by Vincent Pelletier's avatar Vincent Pelletier Committed by Felipe Balbi
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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: default avatarVincent Pelletier <plr.vincent@gmail.com>
Signed-off-by: default avatarFelipe Balbi <felipe.balbi@linux.intel.com>
parent 7e4da3fc

drivers/usb/gadget/function/f_fs.c

+2 −2
Original line number Diff line number Diff line
@@ -2091,8 +2091,8 @@ static int __ffs_data_do_entity(enum ffs_entity_type type, 


	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;

include/uapi/linux/usb/functionfs.h

+1 −0
Original line number Diff line number Diff line
@@ -93,6 +93,7 @@ struct usb_ext_prop_desc { 
 * |   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    |