Hi Lukasz,
Lukasz Majewski lukma@denx.de writes:
Hi Felipe,
Thanks for the patch. Please see my comments below.
On 13 Feb 2017 11:42 am, Felipe Balbi felipe.balbi@linux.intel.com wrote:
Hi,
Marek Vasut marex@denx.de writes:
On 02/10/2017 05:32 PM, Andy Shevchenko wrote:
From: Felipe Balbi felipe.balbi@linux.intel.com
If last packet is short, we shouldn't write req->length bytes to non-volatile media, we should write only what's available to us, which is held in req->actual.
Signed-off-by: Felipe Balbi felipe.balbi@linux.intel.com Signed-off-by: Andy Shevchenko andriy.shevchenko@linux.intel.com
Since I have no clue about DFU internals, I will wait for Lukasz's Ack.
you don't need to have any clues about DFU internals to realise that this fixes an actual bug, see below:
I don't know your exact use case. Please keep in mind that we most
eMMC :-)
work on NAND and eMMC, which require the whole block write.
Well, then the file should have been padded already before sending it over USB, right? :-)
You shouldn't write req->length if you don't receive req->length as you are, potentially, writing garbage to the storage medium :-)
However, I will setup test environment (after changing the job it was gone), test your patch and then let you know.
cool
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