Hi, I'm working on a linux driver for a usb to i2c chip (the MCP2221). The USB chip is USB 2.0 Full Speed, and the driver that I'm working on is here: http://ww1.microchip.com/downloads/en/DeviceDoc/mcp2221_0_1.tar.gz The driver uses HID Interrupt for communication, and both the in and out endpoints have a bInterval of 1. The problem is that the following function (from the above .tar.gz) takes 8ms to complete, when I'm expecting 1 or 2ms maximum. It simply sends a USB packet, then gets the reply. static int mcp2221_ll_cmd(struct i2c_mcp2221 *dev) { int rv; /* tell everybody to leave the URB alone */ dev->ongoing_usb_ll_op = 1; /* submit the interrupt out ep packet */ if (usb_submit_urb(dev->interrupt_out_urb, GFP_KERNEL)) { dev_err(&dev->interface->dev, "mcp2221(ll): usb_submit_urb intr out failed\n"); dev->ongoing_usb_ll_op = 0; return -EIO; } /* wait for its completion */ rv = wait_event_interruptible(dev->usb_urb_completion_wait, (!dev->ongoing_usb_ll_op)); if (rv < 0) { dev_err(&dev->interface->dev, "mcp2221(ll): wait interrupted\n"); goto ll_exit_clear_flag; } /* tell everybody to leave the URB alone */ dev->ongoing_usb_ll_op = 1; /* submit the interrupt in ep packet */ if (usb_submit_urb(dev->interrupt_in_urb, GFP_KERNEL)) { dev_err(&dev->interface->dev, "mcp2221(ll): usb_submit_urb intr in failed\n"); dev->ongoing_usb_ll_op = 0; return -EIO; } /* wait for its completion */ rv = wait_event_interruptible(dev->usb_urb_completion_wait, (!dev->ongoing_usb_ll_op)); if (rv < 0) { dev_err(&dev->interface->dev, "mcp2221(ll): wait interrupted\n"); goto ll_exit_clear_flag; } ll_exit_clear_flag: dev->ongoing_usb_ll_op = 0; return rv; } (Please let me know what information to provide. I have oscilloscope outputs, lsusb outputs, more information about mcp2221, etc. I just didn't want to make this a huge dump of irrelevant information) John Tapsell -- 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
