On Sun, Dec 22, 2013 at 1:47 AM, Greg KH <[email protected]> wrote:
> On Sat, Dec 21, 2013 at 08:19:36PM +0800, Yingchun Li wrote:
>> Hi, I have a box presents to PC as a CDC-ACM device. And I write an simple
>> Application to write data to the box by ttyACM0.
>> The application is a loop that write the data to box, and waiting for
>> the box response
>> the data.
>> The question is , after wrote the data to the box, the box will
>> process the data for a while.
>> before I read the box, it seems
>> the ACM driver will read the box automaticly(I find that from the usb
>> sniffer). and there
>> is a lot of READ-NAK packet.
>> So could the box disable the automatic read by someway such as flow
>> control, and
>> until it ready for sending response?
>
> That is not how the USB protocol works for that type of device. What is
> the problem with the READ-NAK packets?
Thanks a lot.
In fact, the box is not a modem device, and it use a customized protocol to
communicate with PC.
So I use the cdc-acm serial just as a normal serial. On some PC, there are
a lot of READ-bus turnaround timeout errors, so I just want to decrease the read
actions if the box is busy, and expect to reduce the bus turnaround timeout
errors(my box's IN endpoint always receive CLEAR_HALT commands).
I don't want to modify the PC drivers, If there is no easy way to
disable the automatic read,
please Ignore the question.
Thanks!
> greg k-h
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