Switch to using command line to pass master fd. Add manual.

The X server now accepts '-masterfd' as the way to pass the master
file descriptor to the X server.

Signed-off-by: Keith Packard <keithp@keithp.com>

3 files changed, 111 insertions, 13 deletions

diff --git a/Makefile.am b/Makefile.am
index 697f89c..062a916 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -22,6 +22,9 @@
 
 bin_PROGRAMS = xlease
 
+appmandir=$(APP_MAN_DIR)
+appman_DATA=xlease.1
+
 AM_CFLAGS = $(XLEASE_CFLAGS)
 xlease_LDADD = $(XLEASE_LIBS)
 
diff --git a/xlease.1 b/xlease.1
new file mode 100644
index 0000000..724a9a4
--- /dev/null
+++ b/xlease.1
@@ -0,0 +1,83 @@
+.\"
+.\" Copyright © 2018 Keith Packard
+.\"
+.\" Permission to use, copy, modify, distribute, and sell this software and its
+.\" documentation for any purpose is hereby granted without fee, provided that
+.\" the above copyright notice appear in all copies and that both that copyright
+.\" notice and this permission notice appear in supporting documentation, and
+.\" that the name of the copyright holders not be used in advertising or
+.\" publicity pertaining to distribution of the software without specific,
+.\" written prior permission.  The copyright holders make no representations
+.\" about the suitability of this software for any purpose.  It is provided "as
+.\" is" without express or implied warranty.
+.\"
+.\" THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+.\" INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+.\" EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+.\" CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+.\" DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+.\" TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+.\" OF THIS SOFTWARE.
+.\"
+.TH XLEASE 1 "xlease 0.1" "X Version 11"
+.SH NAME
+xlease \- lease an X output for another DRM application
+.SH SYNOPSIS
+.B "xlease"
+.RI [\-\-help] [\-\-verbose]
+.RI [\-\-output \fIoutput\fP]
+.RI [\-\-display \fIdisplay\fP]
+.RI [\-\-fd_arg \fIname\fP]
+.IR <command> <arg> ...
+.SH DESCRIPTION
+.I Xlease
+is used to borrow a set of DRM resources from the X server and hand
+them to another application (potentially another X server) for
+independent use. The resources are leased from the X server DRM master
+and attached to a new DRM master associated with a file
+descriptor. That file descriptor is passed on the command line to the
+application which can then perform KMS operations on the descriptor to
+configure it for display.
+.IP \-\-help
+Print out a usage summary and exit.
+.IP \-\-verbose
+Increase the verbosity of the application, printing out various
+progress messages and other information.
+.IP "\-\-output \fIoutput\fP"
+Borrow the specified output for use. This option is required.
+.IP "\-\-display \fIdisplay\fP"
+Connect to the specified X server.
+.IP "\-\-fd-arg \fIargument-name\fP"
+.I Xlease
+passes the DRM master file descriptor on the command line to the
+application. This option allows the configuration of the flag for that
+value, by default it is “-masterfd”.
+.IP "<command> <arg> ..."
+This specifies the program to be run. By default, this is “X -seat
+seat1 :1”. The fd-arg parameter is added to this, and then the file
+descriptor in decimal, so if no parameters are provided to
+.I xlease
+then the command that will be run is
+.RS
+X -seat seat1 :1 -masterfd 4
+.RE
+.PP
+For this to be able to open suitable input devices, they must first be
+assigned to the specified seat, perhaps by using loginctl, and the
+devices must be accessible by the user running the application.
+.SH EXAMPLES
+Starts another X server on connection :1 for seat 1 using output HDMI-2
+.RS
+xlease --output HDMI-2
+.RE
+.PP
+More verbose example that does exactly the same, just with all
+parameters specified on the command line:
+.RS
+xlease --display :0 --output HDMI-2 -fd-arg -master-fd -- X -seat
+seat1 :1
+.SH "SEE ALSO"
+Xrandr(1), X(1)
+.SH AUTHORS
+Keith Packard,
+keithp@keithp.com
diff --git a/xlease.c b/xlease.c
index 79c48ec..ddaf349 100644
--- a/xlease.c
+++ b/xlease.c
@@ -34,10 +34,13 @@
 
 char *default_x_server[] = {
 	"X",
+	"-seat",
+	"seat1",
+	":1",
 	NULL
 };
 
-#define DEFAULT_ENV		"XF86_VIDEO_MODESETTING_FD"
+#define DEFAULT_FD_ARG		"-masterfd"
 
 /* Lease an output from X and start an X server running on it */
 
@@ -58,7 +61,7 @@ typedef struct {
 	char *display;
 	char *output_name;
 	char **xserver;
-	char *env;
+	char *fd_arg;
 	char *shell;
 	int verbose;
 	xcb_connection_t *conn;
@@ -312,17 +315,17 @@ app_fini(app_t *app)
 }
 
 static const struct option options[] = {
-	{ .name = "output", .has_arg = 1, .val = 'o' },
 	{ .name = "display", .has_arg = 1, .val = 'd' },
+	{ .name = "output", .has_arg = 1, .val = 'o' },
+	{ .name = "fd-arg", .has_arg = 1, .val = 'f' },
 	{ .name = "help", .has_arg = 0, .val = '?' },
 	{ .name = "verbose", .has_arg = 0, .val = 'v' },
-	{ .name = "env", .has_arg = 1, .val = 'e' },
 	{ 0 },
 };
 
 static void usage(char *program, int code)
 {
-	fprintf(stderr, "usage: %s [--display=<display>] [--output=<output>] [--env=<name>] [--verbose] [--help] {X server ...}\n", program);
+	fprintf(stderr, "usage: %s [--display=<display>] [--output=<output>] [--fd-arg=<--name>] [--verbose] [--help] {command args ...}\n", program);
 	exit(code);
 }
 
@@ -334,9 +337,9 @@ int main (int argc, char **argv)
 	init_app(&app);
 
 	app.xserver = default_x_server;
-	app.env = DEFAULT_ENV;
+	app.fd_arg = DEFAULT_FD_ARG;
 
-	while ((c = getopt_long(argc, argv, "?vo:d:x:s:", options, NULL)) != -1) {
+	while ((c = getopt_long(argc, argv, "?vo:d:f:", options, NULL)) != -1) {
 		switch (c) {
 		case 'v':
 			app.verbose++;
@@ -347,8 +350,8 @@ int main (int argc, char **argv)
 		case 'o':
 			app.output_name = optarg;
 			break;
-		case 'e':
-			app.env = optarg;
+		case 'f':
+			app.fd_arg = optarg;
 			break;
 		case '?':
 			usage(argv[0], 0);
@@ -420,13 +423,22 @@ int main (int argc, char **argv)
 		exit(1);
 	}
 
-	if (setenv(app.env, fd_string, 1) < 0) {
-		perror("setenv");
+	int xserver_argc = 0;
+	for (xserver_argc = 0; app.xserver[xserver_argc]; xserver_argc++);
+
+	char **xserver = calloc((xserver_argc + 5), sizeof (char *));
+	if (!xserver) {
+		perror("calloc");
 		exit(1);
 	}
 
-	if (execvp(app.xserver[0], app.xserver)) {
-		perror(app.xserver[0]);
+	memcpy(xserver, app.xserver, xserver_argc * sizeof (char *));
+	xserver[xserver_argc++] = app.fd_arg;
+	xserver[xserver_argc++] = fd_string;
+	xserver[xserver_argc++] = NULL;
+
+	if (execvp(xserver[0], xserver)) {
+		perror(xserver[0]);
 		exit(1);
 	}