mei: bus: enable non-blocking RX

Enable non-blocking receive for drivers on mei bus, this allows checking
for data availability by mei client drivers. This is most effective for
fixed address clients, that lacks flow control.

This function adds new API function mei_cldev_recv_nonblock(), it
retuns -EGAIN if function will block.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 29 insertions, 2 deletions

diff --git a/drivers/misc/mei/bus.c b/drivers/misc/mei/bus.c
index 2fd254ecde2f..0037153c80a6 100644
--- a/drivers/misc/mei/bus.c
+++ b/drivers/misc/mei/bus.c
@@ -98,15 +98,18 @@ out:
  * @cl: host client
  * @buf: buffer to receive
  * @length: buffer length
+ * @mode: io mode
  *
  * Return: read size in bytes of < 0 on error
  */
-ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length)
+ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length,
+		      unsigned int mode)
 {
 	struct mei_device *bus;
 	struct mei_cl_cb *cb;
 	size_t r_length;
 	ssize_t rets;
+	bool nonblock = !!(mode & MEI_CL_IO_RX_NONBLOCK);
 
 	if (WARN_ON(!cl || !cl->dev))
 		return -ENODEV;
@@ -127,6 +130,11 @@ ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length)
 	if (rets && rets != -EBUSY)
 		goto out;
 
+	if (nonblock) {
+		rets = -EAGAIN;
+		goto out;
+	}
+
 	/* wait on event only if there is no other waiter */
 	/* synchronized under device mutex */
 	if (!waitqueue_active(&cl->rx_wait)) {
@@ -192,6 +200,25 @@ ssize_t mei_cldev_send(struct mei_cl_device *cldev, u8 *buf, size_t length)
 EXPORT_SYMBOL_GPL(mei_cldev_send);
 
 /**
+ * mei_cldev_recv_nonblock - non block client receive (read)
+ *
+ * @cldev: me client device
+ * @buf: buffer to receive
+ * @length: buffer length
+ *
+ * Return: read size in bytes of < 0 on error
+ *         -EAGAIN if function will block.
+ */
+ssize_t mei_cldev_recv_nonblock(struct mei_cl_device *cldev, u8 *buf,
+				size_t length)
+{
+	struct mei_cl *cl = cldev->cl;
+
+	return __mei_cl_recv(cl, buf, length, MEI_CL_IO_RX_NONBLOCK);
+}
+EXPORT_SYMBOL_GPL(mei_cldev_recv_nonblock);
+
+/**
  * mei_cldev_recv - client receive (read)
  *
  * @cldev: me client device
@@ -204,7 +231,7 @@ ssize_t mei_cldev_recv(struct mei_cl_device *cldev, u8 *buf, size_t length)
 {
 	struct mei_cl *cl = cldev->cl;
 
-	return __mei_cl_recv(cl, buf, length);
+	return __mei_cl_recv(cl, buf, length, 0);
 }
 EXPORT_SYMBOL_GPL(mei_cldev_recv);