[usb] Allow endpoints to be refilled to a specified upper limit

For USB mass storage devices, we do not want to submit more bulk IN
packets than are required for the inbound data, since this will waste
memory.

Allow an upper limit to be specified on each refill attempt.  The
endpoint will be refilled to the lower of this limit or the limit
specified by usb_refill_init().

Signed-off-by: Michael Brown <mcb30@ipxe.org>

1 files changed, 16 insertions, 3 deletions

diff --git a/src/drivers/bus/usb.c b/src/drivers/bus/usb.c
index 88df9c64a..70a86c913 100644
--- a/src/drivers/bus/usb.c
+++ b/src/drivers/bus/usb.c
@@ -651,12 +651,13 @@ int usb_prefill ( struct usb_endpoint *ep ) {
 }
 
 /**
- * Refill endpoint
+ * Refill endpoint up to specified limit
  *
  * @v ep		USB endpoint
+ * @v max		Fill limit
  * @ret rc		Return status code
  */
-int usb_refill ( struct usb_endpoint *ep ) {
+int usb_refill_limit ( struct usb_endpoint *ep, unsigned int max ) {
 	struct io_buffer *iobuf;
 	size_t reserve = ep->reserve;
 	size_t len = ( ep->len ? ep->len : ep->mtu );
@@ -667,7 +668,9 @@ int usb_refill ( struct usb_endpoint *ep ) {
 	assert ( ep->max > 0 );
 
 	/* Refill endpoint */
-	while ( ep->fill < ep->max ) {
+	if ( max > ep->max )
+		max = ep->max;
+	while ( ep->fill < max ) {
 
 		/* Get or allocate buffer */
 		if ( list_empty ( &ep->recycled ) ) {
@@ -699,6 +702,16 @@ int usb_refill ( struct usb_endpoint *ep ) {
 }
 
 /**
+ * Refill endpoint
+ *
+ * @v ep		USB endpoint
+ * @ret rc		Return status code
+ */
+int usb_refill ( struct usb_endpoint *ep ) {
+	return usb_refill_limit ( ep, ep->max );
+}
+
+/**
  * Discard endpoint recycled buffer list
  *
  * @v ep		USB endpoint