On Sun, Dec 22, 2013 at 1:47 AM, Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx> 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 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
