devctl: add getpath command

Retrieves that path for a device. Different methods to enumerat the path
are supported, called locators.

Sponsored by:		Netflix
Reviewed by:		jhb
Differential Revision:	https://reviews.freebsd.org/D32747

usr.sbin/devctl/devctl.8

@@ -24,7 +24,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd June 1, 2021
+.Dd October 31, 2021
 .Dt DEVCTL 8
 .Os
 .Sh NAME
@@ -74,6 +74,10 @@
 .Cm reset
 .Op Fl d
 .Ar device
+.Nm
+.Cm getpath
+.Ar locator
+.Ar device
 .Sh DESCRIPTION
 The
 .Nm
@@ -214,6 +218,24 @@ tried first; if failed or not implemented, power reset is tried.
 .Pp
 If you have detached or suspended a child device explicitly and then
 do a reset, the child device will end up attached.
+.It Xo Cm getpath
+.Ar locator
+.Ar device
+.Xc
+Prints the full path to the
+.Ar device
+using the
+.Ar locator
+method to get the path name.
+Currently, only the
+.Dq UEFI
+and
+.Dq FreeBSD
+locators are implemented.
+The UEFI locator constructs a path to the device using the rules
+outlines for DEVICE_PATH in the UEFI standard.
+The FreeBSD locator constructs a path back to the root of the tree
+with the nodes separated by slashes.
 .El
 .Sh SEE ALSO
 .Xr devctl 3 ,

usr.sbin/devctl/devctl.c

@@ -84,6 +84,7 @@ usage(void)
 	    "       devctl freeze\n"
 	    "       devctl thaw\n"
 	    "       devctl reset [-d] device\n"
+	    "       devctl getpath locator device\n"
 	    );
 	exit(1);
 }
@@ -420,6 +421,21 @@ reset(int ac, char **av)
 }
 DEVCTL_COMMAND(top, reset, reset);
 
+static int
+getpath(int ac, char **av)
+{
+	char *buffer = NULL;
+
+	if (ac != 3)
+		usage();
+	if (devctl_getpath(av[2], av[1], &buffer) < 0)
+		err(1, "Failed to get path via %s to %s", av[1], av[2]);
+	printf("%s\n", buffer);
+	free(buffer);
+	return (0);
+}
+DEVCTL_COMMAND(top, getpath, getpath);
+
 int
 main(int ac, char *av[])
 {