On Mon, 2015-02-09 at 20:44 +0200, Lauri Kasanen wrote: > On Mon, 09 Feb 2015 11:08:01 +0100 > Oliver Neukum <oneukum@xxxxxxx> wrote: > > > > + ret = usb_interrupt_msg(dev, usb_sndintpipe(dev, 0x02), > > > + buf2, sizeof(buf2), > > > + &transfered, USB_CTRL_SET_TIMEOUT); > > > > You cannot do this. Even for a single byte DMA on the stack is > > wrong. Not on all architectures it works at all and you violate > > the DMA constrainsts. You must use kmalloc(). > > Hi Oliver, > > Does this still apply when using hid_hw_output_report? Yes. For USB devices hid_hw_output_report() goes to usbhid_output_report(). That goes to usb_interrupt_msg(), which passes the buffer pointer. It will then be mapped for DMA. You must not do that on the stack. HTH Oliver -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
