UDS: add support for FIONREAD

Change-Id: I50030012b408242a86f8c55017429acdadff49d1

drivers/uds/ioc_uds.c

@@ -2,11 +2,6 @@
  * Unix Domain Sockets Implementation (PF_UNIX, PF_LOCAL)
  * This code handles ioctl(2) commands to implement the socket API.
  * Some helper functions are also present.
- *
- * The entry points into this file are...
- *
- *   uds_do_ioctl:           process an IOCTL request.
- *   uds_clear_fds:          calls vfs_put_filp for undelivered FDs.
  */
 
 #include "uds.h"
@@ -919,6 +914,20 @@ do_recvmsg(devminor_t minor, endpoint_t endpt, cp_grant_id_t grant)
 	    sizeof(struct msg_control));
 }
 
+static int
+do_fionread(devminor_t minor, endpoint_t endpt, cp_grant_id_t grant)
+{
+	int rc;
+
+	rc = uds_perform_read(minor, NONE, GRANT_INVALID, UDS_BUF, 1);
+
+	/* What should we do on error?  Just set to zero for now. */
+	if (rc < 0)
+		rc = 0;
+
+	return sys_safecopyto(endpt, grant, 0, (vir_bytes) &rc, sizeof(rc));
+}
+
 int
 uds_do_ioctl(devminor_t minor, unsigned long request, endpoint_t endpt,
 	cp_grant_id_t grant)
@@ -1046,6 +1055,14 @@ uds_do_ioctl(devminor_t minor, unsigned long request, endpoint_t endpt,
 
 		break;
 
+	case FIONREAD:
+		/*
+		 * Get the number of bytes immediately available for reading.
+		 */
+		rc = do_fionread(minor, endpt, grant);
+
+		break;
+
 	default:
 		/*
 		 * The IOCTL command is not valid for /dev/uds -- this happens

drivers/uds/uds.c

@@ -2,20 +2,13 @@
  * Unix Domain Sockets Implementation (PF_UNIX, PF_LOCAL)
  * This code handles requests generated by operations on /dev/uds
  *
- * The entry points into this file are...
- *
- *   uds_unsuspend:	resume a previously suspended socket call
- *   main:		driver main loop
- *
- * The interface to unix domain sockets is similar to the interface to network
+ * The interface to UNIX domain sockets is similar to the interface to network
  * sockets. There is a character device (/dev/uds) and this server is a
  * 'driver' for that device.
  */
 
 #include "uds.h"
 
-static ssize_t uds_perform_read(devminor_t, endpoint_t, cp_grant_id_t, size_t,
-	int);
 static ssize_t uds_perform_write(devminor_t, endpoint_t, cp_grant_id_t, size_t,
 	int);
 
@@ -244,7 +237,7 @@ uds_select(devminor_t minor, unsigned int ops, endpoint_t endpt)
 	return ready_ops;
 }
 
-static ssize_t
+ssize_t
 uds_perform_read(devminor_t minor, endpoint_t endpt, cp_grant_id_t grant,
 	size_t size, int pretend)
 {

drivers/uds/uds.h

@@ -197,6 +197,8 @@ int uds_do_ioctl(devminor_t minor, unsigned long request, endpoint_t endpt,
 	cp_grant_id_t grant);
 
 /* uds.c */
+ssize_t uds_perform_read(devminor_t minor, endpoint_t endpt,
+	cp_grant_id_t grant, size_t size, int pretend);
 void uds_unsuspend(devminor_t minor);
 
 /* vfs_uds.c */