This patch supports the separate handling of the USB transfer buffer length and the length of the buffer used for multi packet support. For devices supporting multiple report or diagnostic packets, the USB transfer size is now limited to the USB endpoints wMaxPacketSize - otherwise it defaults to the configured report packet size as before. This fixes an issue where event reporting can be delayed for an arbitrary time for multi packet devices. For instance the report size for eGalax devices is defined to the 16 byte maximum diagnostic packet size as opposed to the 5 byte report packet size. In case the driver requests 16 byte from the USB interrupt endpoint, the USB host controller driver needs to split up the request into 2 accesses according to the endpoints wMaxPacketSize of 8 byte. When the first transfer is answered by the eGalax device with not less than the full 8 byte requested, the host controller has got no way of knowing whether the touch controller has got additional data queued and will issue the second transfer. If per example a liftoff event finishes at such a wMaxPacketSize boundary, the data will not be available to the usbtouch driver until a further event is triggered and transfered to the host. From user perspective the BTN_TOUCH release event in this case is stuck until the next touch down event.
Unified · Split
| @@ -106,6 +106,7 @@ struct usbtouch_device_info { · 105 unmodified lines | ||
| 106 | 106 | struct usbtouch_usb { |
| 107 | 107 | unsigned char *data; |
| 108 | 108 | dma_addr_t data_dma; |
| 109 | + int data_size; | |
| 109 | 110 | unsigned char *buffer; |
| 110 | 111 | int buf_len; |
| 111 | 112 | struct urb *irq; |
| @@ -1523,7 +1524,7 @@ static int usbtouch_reset_resume(struct usb_interface *intf) · 1411 unmodified lines | ||
| 1523 | 1524 | static void usbtouch_free_buffers(struct usb_device *udev, |
| 1524 | 1525 | struct usbtouch_usb *usbtouch) |
| 1525 | 1526 | { |
| 1526 | − usb_free_coherent(udev, usbtouch->type->rept_size, | |
| 1527 | + usb_free_coherent(udev, usbtouch->data_size, | |
| 1527 | 1528 | usbtouch->data, usbtouch->data_dma); |
| 1528 | 1529 | kfree(usbtouch->buffer); |
| 1529 | 1530 | } |
| @@ -1568,7 +1569,20 @@ static int usbtouch_probe(struct usb_interface *intf, · 38 unmodified lines | ||
| 1568 | 1569 | if (!type->process_pkt) |
| 1569 | 1570 | type->process_pkt = usbtouch_process_pkt; |
| 1570 | 1571 | |
| 1571 | − usbtouch->data = usb_alloc_coherent(udev, type->rept_size, | |
| 1572 | + usbtouch->data_size = type->rept_size; | |
| 1573 | + if (type->get_pkt_len) { | |
| 1574 | + /* | |
| 1575 | + * When dealing with variable-length packets we should | |
| 1576 | + * not request more than wMaxPacketSize bytes at once | |
| 1577 | + * as we do not know if there is more data coming or | |
| 1578 | + * we filled exactly wMaxPacketSize bytes and there is | |
| 1579 | + * nothing else. | |
| 1580 | + */ | |
| 1581 | + usbtouch->data_size = min(usbtouch->data_size, | |
| 1582 | + usb_endpoint_maxp(endpoint)); | |
| 1583 | + } | |
| 1584 | + | |
| 1585 | + usbtouch->data = usb_alloc_coherent(udev, usbtouch->data_size, | |
| 1572 | 1586 | GFP_KERNEL, &usbtouch->data_dma); |
| 1573 | 1587 | if (!usbtouch->data) |
| 1574 | 1588 | goto out_free; |
| @@ -1628,12 +1642,12 @@ static int usbtouch_probe(struct usb_interface *intf, · 53 unmodified lines | ||
| 1628 | 1642 | if (usb_endpoint_type(endpoint) == USB_ENDPOINT_XFER_INT) |
| 1629 | 1643 | usb_fill_int_urb(usbtouch->irq, udev, |
| 1630 | 1644 | usb_rcvintpipe(udev, endpoint->bEndpointAddress), |
| 1631 | − usbtouch->data, type->rept_size, | |
| 1645 | + usbtouch->data, usbtouch->data_size, | |
| 1632 | 1646 | usbtouch_irq, usbtouch, endpoint->bInterval); |
| 1633 | 1647 | else |
| 1634 | 1648 | usb_fill_bulk_urb(usbtouch->irq, udev, |
| 1635 | 1649 | usb_rcvbulkpipe(udev, endpoint->bEndpointAddress), |
| 1636 | − usbtouch->data, type->rept_size, | |
| 1650 | + usbtouch->data, usbtouch->data_size, | |
| 1637 | 1651 | usbtouch_irq, usbtouch); |
| 1638 | 1652 | |
| 1639 | 1653 | usbtouch->irq->dev = udev; |