Warn users of URB_NO_SETUP_DMA_MAP about xHCI behavior. Device drivers can choose to DMA map the setup packet of a control transfer before submitting the URB to the USB core. Drivers then set the URB_NO_SETUP_DMA_MAP and pass in the DMA memory address in setup_dma, instead of providing a kernel address for setup_packet. However, xHCI requires that the setup packet be copied into an internal data structure, and we need a kernel memory address pointer for that. Warn users of URB_NO_SETUP_DMA_MAP that they should provide a valid pointer for setup_packet, along with the DMA address. FIXME: I'm not entirely sure how to work around this in the xHCI driver or USB core. Signed-off-by: Sarah Sharp <sarah.a.sharp@xxxxxxxxxxxxxxx> --- include/linux/usb.h | 4 +++- 1 files changed, 3 insertions(+), 1 deletions(-) diff --git a/include/linux/usb.h b/include/linux/usb.h index 2b8845b..d673d05 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -1045,7 +1045,9 @@ typedef void (*usb_complete_t)(struct urb *); * @setup_dma: For control transfers with URB_NO_SETUP_DMA_MAP set, the * device driver has provided this DMA address for the setup packet. * The host controller driver should use this in preference to - * setup_packet. + * setup_packet, but the HCD may chose to ignore the address if it must + * copy the setup packet into internal structures. Therefore, setup_packet + * must always point to a valid buffer. * @start_frame: Returns the initial frame for isochronous transfers. * @number_of_packets: Lists the number of ISO transfer buffers. * @interval: Specifies the polling interval for interrupt or isochronous -- 1.5.6.5 -- 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
