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 <[e-mail]>
Signed-off-by: Tomas Winkler <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/misc/mei/bus-fixup.c

···
 	if (ret < 0)
 		return ret;
 
-	ret = __mei_cl_recv(cldev->cl, buf, length);
+	ret = __mei_cl_recv(cldev->cl, buf, length, 0);
 	if (ret < 0)
 		return ret;
 
···
 		return -ENOMEM;
 
 	ret = 0;
-	bytes_recv = __mei_cl_recv(cl, (u8 *)reply, if_version_length);
+	bytes_recv = __mei_cl_recv(cl, (u8 *)reply, if_version_length, 0);
 	if (bytes_recv < if_version_length) {
 		dev_err(bus->dev, "Could not read IF version\n");
 		ret = -EIO;

drivers/misc/mei/bus.c

···
  * @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;
···
 	rets = mei_cl_read_start(cl, length, NULL);
 	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 */
···
 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
···
 {
 	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);
 

drivers/misc/mei/mei_dev.h

···
  *
  * @MEI_CL_IO_TX_BLOCKING: send is blocking
  * @MEI_CL_IO_TX_INTERNAL: internal communication between driver and FW
+ *
+ * @MEI_CL_IO_RX_NONBLOCK: recv is non-blocking
  */
 enum mei_cl_io_mode {
 	MEI_CL_IO_TX_BLOCKING = BIT(0),
 	MEI_CL_IO_TX_INTERNAL = BIT(1),
+
+	MEI_CL_IO_RX_NONBLOCK = BIT(2),
 };
 
 /*
···
 void mei_cl_bus_dev_fixup(struct mei_cl_device *dev);
 ssize_t __mei_cl_send(struct mei_cl *cl, u8 *buf, size_t length,
 		      unsigned int mode);
-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);
 bool mei_cl_bus_rx_event(struct mei_cl *cl);
 bool mei_cl_bus_notify_event(struct mei_cl *cl);
 void mei_cl_bus_remove_devices(struct mei_device *bus);

include/linux/mei_cl_bus.h

···
 /**
  * module_mei_cl_driver - Helper macro for registering mei cl driver
  *
- * @__mei_cldrv mei_cl_driver structure
+ * @__mei_cldrv: mei_cl_driver structure
  *
  *  Helper macro for mei cl drivers which do not do anything special in module
  *  init/exit, for eliminating a boilerplate code.
···
 		      mei_cldev_driver_unregister)
 
 ssize_t mei_cldev_send(struct mei_cl_device *cldev, u8 *buf, size_t length);
-ssize_t  mei_cldev_recv(struct mei_cl_device *cldev, u8 *buf, size_t length);
+ssize_t mei_cldev_recv(struct mei_cl_device *cldev, u8 *buf, size_t length);
+ssize_t mei_cldev_recv_nonblock(struct mei_cl_device *cldev, u8 *buf,
+				size_t length);
 
 int mei_cldev_register_rx_cb(struct mei_cl_device *cldev, mei_cldev_cb_t rx_cb);
 int mei_cldev_register_notif_cb(struct mei_cl_device *cldev,