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Diffstat (limited to 'drivers/usb/core/usb.c')
| -rw-r--r-- | drivers/usb/core/usb.c | 32 |
1 files changed, 32 insertions, 0 deletions
diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c index 8f07b0516100..a566bb494e24 100644 --- a/drivers/usb/core/usb.c +++ b/drivers/usb/core/usb.c @@ -748,6 +748,38 @@ void usb_put_intf(struct usb_interface *intf) } EXPORT_SYMBOL_GPL(usb_put_intf); +/** + * usb_intf_get_dma_device - acquire a reference on the usb interface's DMA endpoint + * @intf: the usb interface + * + * While a USB device cannot perform DMA operations by itself, many USB + * controllers can. A call to usb_intf_get_dma_device() returns the DMA endpoint + * for the given USB interface, if any. The returned device structure must be + * released with put_device(). + * + * See also usb_get_dma_device(). + * + * Returns: A reference to the usb interface's DMA endpoint; or NULL if none + * exists. + */ +struct device *usb_intf_get_dma_device(struct usb_interface *intf) +{ + struct usb_device *udev = interface_to_usbdev(intf); + struct device *dmadev; + + if (!udev->bus) + return NULL; + + dmadev = get_device(udev->bus->sysdev); + if (!dmadev || !dmadev->dma_mask) { + put_device(dmadev); + return NULL; + } + + return dmadev; +} +EXPORT_SYMBOL_GPL(usb_intf_get_dma_device); + /* USB device locking * * USB devices and interfaces are locked using the semaphore in their |