[PATCH v3 1/2] drivers: usb/core/urb: Add URB_FREE_COHERENT

[Rhett Aultman <rhett.aultman@samsara.com>]

From: Vincent Mailhol <mailhol.vincent@wanadoo.fr>

When allocating URB memory with kmalloc(), drivers can simply set the
URB_FREE_BUFFER flag in urb::transfer_flags and that way, the memory
will be freed in the background when killing the URB (for example with
usb_kill_anchored_urbs()).

However, there are no equivalent mechanism when allocating DMA memory
(with usb_alloc_coherent()).

This patch adds a new flag: URB_FREE_COHERENT. Setting this flag will
cause the kernel to automatically call usb_free_coherent() on the
transfer buffer when the URB is killed, similarly to how
URB_FREE_BUFFER triggers a call to kfree().

In order to have all the flags in numerical order, URB_DIR_IN is
renumbered from 0x0200 to 0x0400 so that URB_FREE_COHERENT can reuse
value 0x0200.

Co-developed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
Co-developed-by: Rhett Aultman <rhett.aultman@samsara.com>
Signed-off-by: Rhett Aultman <rhett.aultman@samsara.com>
Reviewed-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
---
 drivers/usb/core/urb.c | 5 ++++-
 include/linux/usb.h    | 3 ++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index 33d62d7e3929..36c48fb196e0 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -22,6 +22,9 @@ static void urb_destroy(struct kref *kref)
 
 	if (urb->transfer_flags & URB_FREE_BUFFER)
 		kfree(urb->transfer_buffer);
+	else if (urb->transfer_flags & URB_FREE_COHERENT)
+		usb_free_coherent(urb->dev, urb->transfer_buffer_length,
+				  urb->transfer_buffer, urb->transfer_dma);
 
 	kfree(urb);
 }
@@ -504,7 +507,7 @@ int usb_submit_urb(struct urb *urb, gfp_t mem_flags)
 
 	/* Check against a simple/standard policy */
 	allowed = (URB_NO_TRANSFER_DMA_MAP | URB_NO_INTERRUPT | URB_DIR_MASK |
-			URB_FREE_BUFFER);
+			URB_FREE_BUFFER | URB_FREE_COHERENT);
 	switch (xfertype) {
 	case USB_ENDPOINT_XFER_BULK:
 	case USB_ENDPOINT_XFER_INT:
diff --git a/include/linux/usb.h b/include/linux/usb.h
index 60bee864d897..945d68ea1d76 100644
--- a/include/linux/usb.h
+++ b/include/linux/usb.h
@@ -1328,9 +1328,10 @@ extern int usb_disabled(void);
 #define URB_NO_INTERRUPT	0x0080	/* HINT: no non-error interrupt
 					 * needed */
 #define URB_FREE_BUFFER		0x0100	/* Free transfer buffer with the URB */
+#define URB_FREE_COHERENT	0x0200  /* Free DMA memory of transfer buffer */
 
 /* The following flags are used internally by usbcore and HCDs */
-#define URB_DIR_IN		0x0200	/* Transfer from device to host */
+#define URB_DIR_IN		0x0400	/* Transfer from device to host */
 #define URB_DIR_OUT		0
 #define URB_DIR_MASK		URB_DIR_IN
 
-- 
2.30.2