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usb: add a hcd_uses_dma helper

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The USB buffer allocation code is the only place in the usb core (and in
fact the whole kernel) that uses is_device_dma_capable, while the URB
mapping code uses the uses_dma flag in struct usb_bus.  Switch the buffer
allocation to use the uses_dma flag used by the rest of the USB code,
and create a helper in hcd.h that checks this flag as well as the
CONFIG_HAS_DMA to simplify the caller a bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20190811080520.21712-3-hch@lst.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christoph Hellwig
2019-08-11 10:05:16 +02:00
committed by Greg Kroah-Hartman
parent dd3ecf17ba
commit edfbcb321f
5 changed files with 10 additions and 11 deletions
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2
include/linux/usb.h
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@@ -1457,7 +1457,7 @@ typedef void (*usb_complete_t)(struct urb *);
* field rather than determining a dma address themselves.
*
* Note that transfer_buffer must still be set if the controller
* does not support DMA (as indicated by bus.uses_dma) and when talking
* does not support DMA (as indicated by hcd_uses_dma()) and when talking
* to root hub. If you have to trasfer between highmem zone and the device
* on such controller, create a bounce buffer or bail out with an error.
* If transfer_buffer cannot be set (is in highmem) and the controller is DMA