Hi All
I have been debugging some usb errors that I have been encountering and here are my conclusions:
-- The error is a BULK IN transfer error, after adding further code to display the internal message:
BULK IN transfer error; rc=-5 : libusb0-dll:err [_usb_reap_async] reaping request failed, win error: A device attached to the system is not functioning.
-- BUT when I used USBLyzer to analyze the underlying problem, it's actually a [buffer overflow] problem.
1) According to usb specification, USB full speed device maximum data packet payload size is 1023
http://www.usb.org/developers/docs/usb_20_070113.zip
2) According to the AT91SAM7S device specification, its USB endpoint size is 64 bytes.
3) According to libusb api description, bulk transfer overflow is caused by too small buffer ( http://libusb.sourceforge.net/api-1.0/packetoverflow.html ). Should use multiple of the device payload size.
4) Since we don't have a size indicator in our USB protocol (our header is 4 bytes, indicating ATR, wait timeout flag etc), the client software must not see more than 1 req_ctx per bulk_usb_transfer call
Therefore, we SHOULD:
A << Use a multiple of 64 bytes as req_ctx size, and must be <= 1023
[per USB specification]. I chose 960. Consequently, there is only ONE size for req_ctx, no more large / small)
B << Desktop/Host software MUST use the same size in static void
run_mainloop(struct usb_dev_handle *devh). Otherwise, multiple req_ctx WILL be combined by the usb driver / libusb and the additional req_ctx header in the middle will confuse the apdu_splitter
On Wed, Sep 4, 2013 at 10:37 PM, Min Xu mxu@sanjole.com wrote:
Hi Harald
Thank you for getting back to me so quickly. I am using Emacs on an Ubuntu netbook to do the edits, which likes to reformat sections as I move (copy/paste section around) and I haven't figured out a command to undo those changes. It'd be nice if there is a .emacsrc or something that automatically formats the code to the project standard? (presumably someone has one? ..)
I started only wanted to make one change and submit (was initially the req_ctx), but couldn't reliably verify it until the debugp was working better without affecting the system, so the changes ballooned up to this stage. So I wanted to submit the changes before I change the code further. I will try limit the scope of changes in my future updates.
To your questions:
- The numerical values of the RCTX_STATE are changed to facilitate the
choosing of the FIFO/double linked list of req_ctx to use. An array of FIFO, using the state to index into the array to get the FIFO is simplest. When I looked how the reqctx_find / ... functions are used, I found all callers use the constant name rather than any specific numeric value.
- I will look at this tomorrow. But I was under the impression on how
the lib_Atmel?? (sorry, can't access the source at the moment) was invoked to install the irq handler, that the entry point to the interrupt would be directly the function passed in. I looked at the sysirq_handler.c?? more closely than the other so I wasn't aware of the Cstartup.c file
Since I increased the req_ctx buffer size to 1kb each, most req_ctx that are transferred to pc contain many many apdus but very often, the req_ctx do not begin at the start of an apdu. So I would like to have an offset (2 byte, since it could be > 256) to indicate the position of the first start of an apdu. After thinking about it more, I would also like to add a sequence number into the header (making the header 8 bytes then?) to better allow for detecting dropped req_ctx (if there are any..). The offset would be 8 for a req_ctx that starts with a new APDU, and would be 0 for an req_ctx that only contains a middle or last fragment of an APDU.
I have already modified the host software to run on Windows (currently using Windows 7 x64), so I will probably make those changes locally only to help me detect any problem I might still be facing.
Again, thank you very much for getting back so quickly, and I appreciate your product very much.
Best Regards
On Wed, Sep 4, 2013 at 9:31 PM, Harald Welte laforge@gnumonks.org wrote:
Dear Min Xu,
On Wed, Sep 04, 2013 at 07:47:46PM -1000, Min Xu wrote:
I made a bunch of changes that significantly improved my test scenario:
I _really_ appreciate your excellent technical work. However, I would like you to go the little extra effort it takes to 'properly' interact with community based Free Software projects, where there are rules like
- only one feature / logical change per patch, resulting in a series of incremental patches, each taking us one step further, each rendering a compile-able and functional build after being applied.
- no re-formatting of code (whitespace changes)
- no patch for local changes like different compiler name in Makefile
- stick to coding style of the project (tab-wide indent, ...) for consistency
- remove old/dead code rather than comment it out (RCTX_STATE_...)
- avoid asm() statements whenever possible. If you need them, please wrap them in an inline C function with descriptive name.
Some quesetions:
why did the numberic values of RCTX_STATE_* have t be changed rather than amended by your new values, keeping the old ones as-is?
interrupt nesting _should_ have been active all the time, see IRQ_Handler_Entry in Cstartup.S, where we first save SPSR and then un-set the IRQ and FIQ bits _before_ branching to the interrupt handler function:
/*- Enable Interrupt and Switch in Supervisor Mode */ msr CPSR_c, #ARM_MODE_SVCWhere ARM_MODE_SVC is set to 0x13, i.e. without 0x40 or 0x80.
So if there's something wrong with the existing code, it should be fixed there rather than two copies of inline-asm in the USART and USB IRQ handler routines.
So I do want to merge this very much, but I think it needs clean-up before it can be merged. I don't expect to have much time for this in the next couple of weeks, so I would be happy if either you or somebody else on the list could work on this.
Regarding your comment about changing the USB protocol: This would lead to host / firmware version incompatibilities, and I'd like to avoid that if possible in any way. We already have the simtrace_hdr.flags structure member, which contains things like SIMTRACE_FLAG_ATR. I'm not sure if I understand your request fully, but why not simply add flags like:
- First fragment of a fragmented APDU
- More fragments to follow for this APDU
This way a new APDU still has to start at the beginning of a USB transfer, but no changes to the simtrace_hdr are required.
Thanks again, Harald
--
- Harald Welte laforge@gnumonks.org
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