dfu: handle short frame result of UPLOAD in state_dfu_idle

In DFU v1.1 specification [1] the DFU_UPLOAD (Short Frame)
is handled only in dfuUPLOADIDLE state:

- Figure A.1 Interface state transition diagram

- the state description in chapter A.2

A.2.3 State 2 dfuIDLE
  on Receipt of the DFU_UPLOAD request,and bitCanUpload = 1
  the Next State is dfuUPLOADIDLE

A.2.10 State 9 dfuUPLOAD-IDLE
  When the length of the data transferred by the device in response
  to a DFU_UPLOAD request is less than wLength. (Short frame)
  the Next State is dfuIDLE

In current code, when an UPLOAD is completely performed after the first
request (for example with wLength=200 and data read = 9), the DFU state
stay at dfuUPLOADIDLE until receiving a DFU_UPLOAD or a DFU_ABORT request
even it is unnecessary as the previous DFU_UPLOAD request already reached
the EOF.

This patch proposes to finish the DFU uploading (don't go to dfuUPLOADIDLE)
and completes the control-read operation (go to DFU_STATE_dfuIDLE) when
the first UPLOAD response has a short frame as an end of file (EOF)
indicator even if it is not explicitly allowed in the DFU specification
but this seems logical.

[1] https://www.usb.org/sites/default/files/DFU_1.1.pdf

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/usb/gadget/f_dfu.c b/drivers/usb/gadget/f_dfu.c
index 4bedc7d..e9340ff 100644
--- a/drivers/usb/gadget/f_dfu.c
+++ b/drivers/usb/gadget/f_dfu.c
@@ -336,6 +336,8 @@ static int state_dfu_idle(struct f_dfu *f_dfu,
 		f_dfu->dfu_state = DFU_STATE_dfuUPLOAD_IDLE;
 		f_dfu->blk_seq_num = 0;
 		value = handle_upload(req, len);
+		if (value >= 0 && value < len)
+			f_dfu->dfu_state = DFU_STATE_dfuIDLE;
 		break;
 	case USB_REQ_DFU_ABORT:
 		/* no zlp? */