[U-Boot] [PATCH v1] usb: gadget: f_dfu: write req->actual bytes

[Lukasz Majewski <lukma@denx.de>]

Hi Felipe,

> 
> Hi Lukasz,
> 
> Lukasz Majewski <lukma@denx.de> writes:
> >> >  >> drivers/usb/gadget/f_dfu.c | 2 +- 
> >> >  >> 1 file changed, 1 insertion(+), 1 deletion(-) 
> >> >  >> 
> >> >  >> diff --git a/drivers/usb/gadget/f_dfu.c
> >> >  >> b/drivers/usb/gadget/f_dfu.c index 8e7c981657..64cdfa7c98
> >> >  >> 100644 --- a/drivers/usb/gadget/f_dfu.c 
> >> >  >> +++ b/drivers/usb/gadget/f_dfu.c 
> >> >  >> @@ -159,7 +159,7 @@ static void
> >> >  >> dnload_request_complete(struct usb_ep *ep, struct
> >> >  >> usb_request *req) int ret; 
> >> >  >> 
> >> >  >> ret = dfu_write(dfu_get_entity(f_dfu->altsetting), req->buf, 
> >> >  >> - req->length, f_dfu->blk_seq_num); 
> >> >  >> + req->actual, f_dfu->blk_seq_num); 
> >> >
> >> >  DFU driver queues a request to USB controller. Per the gadget
> >> > API req->length contains maximum amount of data to be 
> >> >  transmitted. req->actual is written by USB controller with the
> >> > actual amount of data that we transmitted. 
> >> >
> >> >  In the case of IN (TX), upon completion req->length and
> >> > req->actual should always be equal (unless errors show up, etc) 
> >> >
> >> >  In the case of OUT (RX), upon completion req->actual MAY BE less
> >> > than req->length and that's not an error. Say host sent us a
> >> > short packet which causes early termination of transfer. 
> >> >
> >> >  With that in mind, let's consider the situation where we're
> >> > receiving data from host using DFU. Let's assume that we have a
> >> > 4096 byte buffer for transfers and we're receiving a binary
> >> > that's 7679 bytes in size. 
> >> >
> >> >  Here's what we will do (pseudo-code): 
> >> >
> >> >  int remaining = 7679; 
> >> >  char buf[4096]; 
> >> >
> >> >  while (remaining) { 
> >> >  req->length = 4096; 
> >> >  req->buf = buf; 
> >> >  usb_ep_queue(req); 
> >> >
> >> >  /* wait for completion */ 
> >> >
> >> >  remaining -= req->actual; 
> >> >
> >> >  dfu_write(buf, req->length); /* this is the error */ 
> >> >  } 
> >> >
> >> >  Can you see here that in the last packet we will write 4096
> >> > bytes when we should write only 3583? 
> >> >
> >> > In principle you are right. I need to check if this change will
> >> > not introduce regressions.
> >> >
> >> > Can you share your use case?
> >> 
> >> Intel Edison running v2017.03-rc1 + patches (see [1]), flashing
> >> u-boot.bin over DFU (see [2] for details). Without $subject, image
> >> has to be aligned to 4096 bytes as below:
> >> 
> >> $ dd if=u-boot.bin of=u-boot-4k.bin bs=4k seek=1 && truncate -s
> >> %4096 u-boot-4k.bin
> >> 
> >> With $subject, I don't need truncate. We still need the 4096 byte
> >> of zeroes in the beginning of the image for other reasons (which I
> >> really don't know why at this point).
> >> 
> >> [1] https://github.com/andy-shev/u-boot/tree/edison
> >> [2] https://communities.intel.com/message/435516#435516
> >> 
> >
> > Ok. I will check this. Thanks for pointing out :-)
> 
> Any updates here? I'd like to send Tangier Soc and Intel Edison Board
> support but I kinda depend on this patch making upstream. I can resend
> as part of the "add intel edison" series.
> 
> Let me know

I'm setting up /test/py/dfu now on BBB. I will let you know by EOD.

> 




Best regards,

Lukasz Majewski

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