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

[Felipe Balbi]

Hi Lukasz,

Lukasz Majewski <lukma at 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

-- 
balbi
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