[PATCH] usb: gadget: Support transfers from device memory

[Manan Aurora <maurora@google.com>]

USB gadget stack only supports usb_request objects that point to buffers
located in memory. Support use cases where data is transferred from
physical addresses in device mmio regions

Added a bit "pre_mapped" to usb_request to bypass dma_map_single and
dma_map_sg for such requests

The caller must determine the dma address for the request before queuing
it

Signed-off-by: Manan Aurora <maurora@google.com>
---
 drivers/usb/gadget/udc/core.c | 4 ++--
 include/linux/usb/gadget.h    | 1 +
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/udc/core.c b/drivers/usb/gadget/udc/core.c
index ded9531f141b..236165ba08f4 100644
--- a/drivers/usb/gadget/udc/core.c
+++ b/drivers/usb/gadget/udc/core.c
@@ -900,7 +900,7 @@ EXPORT_SYMBOL_GPL(usb_gadget_activate);
 int usb_gadget_map_request_by_dev(struct device *dev,
 		struct usb_request *req, int is_in)
 {
-	if (req->length == 0)
+	if (req->pre_mapped || req->length == 0)
 		return 0;
 
 	if (req->num_sgs) {
@@ -948,7 +948,7 @@ EXPORT_SYMBOL_GPL(usb_gadget_map_request);
 void usb_gadget_unmap_request_by_dev(struct device *dev,
 		struct usb_request *req, int is_in)
 {
-	if (req->length == 0)
+	if (req->pre_mapped || req->length == 0)
 		return;
 
 	if (req->num_mapped_sgs) {
diff --git a/include/linux/usb/gadget.h b/include/linux/usb/gadget.h
index a771ccc038ac..6bc035439098 100644
--- a/include/linux/usb/gadget.h
+++ b/include/linux/usb/gadget.h
@@ -111,6 +111,7 @@ struct usb_request {
 	unsigned		zero:1;
 	unsigned		short_not_ok:1;
 	unsigned		dma_mapped:1;
+	unsigned		pre_mapped:1;
 
 	void			(*complete)(struct usb_ep *ep,
 					struct usb_request *req);
-- 
2.42.0.820.g83a721a137-goog