On Thu, 22 Aug 2013, Florian Echtler wrote: > Hello everyone, > > I recently wanted to pick up again on developing a kernel input driver > for the Microsoft Pixelsense (formerly Surface 2.0). I already have a > working user space driver (see also [1]). > > However - just like last year [2] - I quickly ran into an issue with a > corrupted device firmware after some brief experimentation with the > kernel driver, while the user space driver didn't and doesn't show any > such issues. This happened on two separate Pixelsense devices, with > different kernel versions. > > So even though userspace and kernel driver look like they perform > exactly the same operations on the device, there must be some difference > I don't understand - perhaps libusb does some kind of internal error > handling which the kernel doesn't do? > > > Userspace version: > > // for control commands > usb_control_msg(handle, 0xC0, cmd, 0x00, index, (char*)buf, len, 1000); > > // for bulk data transfer > uint8_t buffer[512]; > result = usb_bulk_read( handle, 0x86, (char*)(buffer), sizeof(buffer), > 1000 ); > > > Kernel version: > > // for control commands > #define surface_command(dev, command, index, buffer, size) > usb_control_msg (dev->usbdev, usb_rcvctrlpipe (dev->usbdev, 0), > command, USB_TYPE_VENDOR | USB_RECIP_ENDPOINT | USB_DIR_IN, 0x00, > index, buffer, size, 1000) This isn't equivalent to the userspace version. Here the recipient is USB_RECIP_ENDPOINT, but in the userspace version it is USB_RECIP_DEVICE. To put it another way, here the bRequestType value is 0xC2 and there it is 0xC0. > // for bulk data transfer > result = usb_bulk_msg (surface->usbdev, > usb_rcvbulkpipe (surface->usbdev, 0x86), > surface->bulk_in_buffer, 512, &bulk_read, 1000); This is equivalent to the version above. > Can anybody venture a guess what kind of functional difference there is > between these code snippets? It's hard to say exactly. Probably one of the control messages will work and the other one won't. Alan Stern -- 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
