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path: root/drivers/usb/core/usb.c
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Diffstat (limited to 'drivers/usb/core/usb.c')
-rw-r--r--drivers/usb/core/usb.c32
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