Hi Christian, On Tue, Oct 15, 2013 at 04:50:00PM +0200, Christian Engelmayer wrote: > This patch supports the separate handling of the USB transfer buffer length > and the length of the buffer used for multi packet support. The USB transfer > size can now be explicitly configured via the device_info record. Otherwise > it defaults to the configured report packet size as before. For devices > supporting multiple report or diagnostic packets, the USB transfer size is > now reduced to the USB endpoints wMaxPacketSize if not explicitly set. > > 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. > > Signed-off-by: Christian Engelmayer <christian.engelma...@frequentis.com> > --- > drivers/input/touchscreen/usbtouchscreen.c | 16 ++++++++++++---- > 1 files changed, 12 insertions(+), 4 deletions(-) > > diff --git a/drivers/input/touchscreen/usbtouchscreen.c > b/drivers/input/touchscreen/usbtouchscreen.c > index 721fdb3..aa1f6a7 100644 > --- a/drivers/input/touchscreen/usbtouchscreen.c > +++ b/drivers/input/touchscreen/usbtouchscreen.c > @@ -76,6 +76,7 @@ struct usbtouch_device_info { > int min_yc, max_yc; > int min_press, max_press; > int rept_size; > + int xmit_size; > > /* > * Always service the USB devices irq not just when the input device is > @@ -1523,7 +1524,7 @@ static int usbtouch_reset_resume(struct usb_interface > *intf) > static void usbtouch_free_buffers(struct usb_device *udev, > struct usbtouch_usb *usbtouch) > { > - usb_free_coherent(udev, usbtouch->type->rept_size, > + usb_free_coherent(udev, usbtouch->type->xmit_size, > usbtouch->data, usbtouch->data_dma); > kfree(usbtouch->buffer); > } > @@ -1567,8 +1568,15 @@ static int usbtouch_probe(struct usb_interface *intf, > usbtouch->type = type; > if (!type->process_pkt) > type->process_pkt = usbtouch_process_pkt; > + if (!type->xmit_size) { > + if ((type->get_pkt_len) && > + (type->rept_size > le16_to_cpu(endpoint->wMaxPacketSize))) > + type->xmit_size = le16_to_cpu(endpoint->wMaxPacketSize); > + else > + type->xmit_size = type->rept_size;
'type' points to a shared data structure and should not be modified. It looks like we already violating this so a cleanup patch would be appreciated as well. BTW, maybe we should do: u16 wMaxPaxetSize = le16_to_cpu(endpoint->wMaxPacketSize); xmit_size = min(type->rept_size, wMaxPaxetSize); ? Thanks. -- Dmitry -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html