logind: expose CanGraphical and CanTTY properties on seat objects

Since we boot so fast now that gdm might get started before the
graphics drivers are properly loaded and probed we might end up
announcing seat0 to gdm before it has graphics capabilities. Which will
cause gdm/X11 cause to fail later on.

To fix this race, let's expose CanGraphical and CanTTY fields on all
seats, which clarify whether a seat is suitable for gdm resp, suitable
for text logins. gdm then needs to watch CanGraphical and spawn X11 on
it only if it is true.

This way:

USB graphics seats will expose CanGraphical=yes, CanTTY=no

Machines with no graphics drivers at all, but a text console:
CanGraphical=no, CanTTY=yes

Machines with CONFIG_VT turned off: CanGraphical=yes, CanTTY=no

And the most important case: seat0 where the graphics driver has not
been probed yet boot up with CanGraphical=no, CanTTY=yes first, which
then changes to CanGraphical=yes as soon as the probing is complete.

TODO

@@ -12,8 +12,6 @@ Bugfixes:
 
 * make anaconda write timeout=0 for encrypted devices
 
-* make sure timeouts are applied to Type=oneshot services.
-
 * Dangling symlinks of .automount unit files in .wants/ directories, set up
   automount points even when the original .automount file did not exist
   anymore. Only the .mount unit was still around.
@@ -27,16 +25,19 @@ Bugfixes:
 
 Features:
 
-* introduce CanGraphics and CanText properties on seat objects, to combat races where gdm is started before the graphics driver is loaded and finished probing.
+* support rd.luks= kernel cmdline params in cryptsetup generator
 
-* change $NOTIFY_SOCKET to use an abstract namespace socket, so that chroot() is compatible with this
-  https://bugzilla.redhat.com/show_bug.cgi?id=833105
+* support rd.fstab= kernel cmdline params in fstab generator
+
+* support rd.driver= kernel cmdline params in modules load
+
+* supprto rd.xxx wherever else makes sense
 
 * readahead: merge the three tools into one binary
 
 * systemctl: when stopping a service which has triggres and warning about it actually check the TriggeredBy= deps fields
 
-* send bus signal to upower on resume so that it can send out its dbus signal for compat
+* send SIGPWR to upower on resume so that it can send out its dbus signal for compat
 
 * vtconsole: don't override kernel cmdline utf8 override setting
 

src/login/logind-device.c

@@ -65,22 +65,32 @@ void device_free(Device *d) {
 }
 
 void device_detach(Device *d) {
+        Seat *s;
         assert(d);
 
-        if (d->seat)
-                LIST_REMOVE(Device, devices, d->seat->devices, d);
+        if (!d->seat)
+                return;
 
-        seat_add_to_gc_queue(d->seat);
+        s = d->seat;
+        LIST_REMOVE(Device, devices, d->seat->devices, d);
         d->seat = NULL;
+
+        seat_add_to_gc_queue(s);
+        seat_send_changed(s, "CanGraphical\0");
 }
 
 void device_attach(Device *d, Seat *s) {
         assert(d);
         assert(s);
 
+        if (d->seat == s)
+                return;
+
         if (d->seat)
                 device_detach(d);
 
         d->seat = s;
         LIST_PREPEND(Device, devices, s->devices, d);
+
+        seat_send_changed(s, "CanGraphical\0");
 }

src/login/logind-seat-dbus.c

@@ -36,6 +36,8 @@
         "  <property name=\"Id\" type=\"s\" access=\"read\"/>\n"        \
         "  <property name=\"ActiveSession\" type=\"so\" access=\"read\"/>\n" \
         "  <property name=\"CanMultiSession\" type=\"b\" access=\"read\"/>\n" \
+        "  <property name=\"CanTTY\" type=\"b\" access=\"read\"/>\n" \
+        "  <property name=\"CanGraphical\" type=\"b\" access=\"read\"/>\n" \
         "  <property name=\"Sessions\" type=\"a(so)\" access=\"read\"/>\n" \
         "  <property name=\"IdleHint\" type=\"b\" access=\"read\"/>\n"  \
         "  <property name=\"IdleSinceHint\" type=\"t\" access=\"read\"/>\n" \
@@ -133,7 +135,7 @@ static int bus_seat_append_sessions(DBusMessageIter *i, const char *property, vo
         return 0;
 }
 
-static int bus_seat_append_multi_session(DBusMessageIter *i, const char *property, void *data) {
+static int bus_seat_append_can_multi_session(DBusMessageIter *i, const char *property, void *data) {
         Seat *s = data;
         dbus_bool_t b;
 
@@ -149,6 +151,38 @@ static int bus_seat_append_multi_session(DBusMessageIter *i, const char *propert
         return 0;
 }
 
+static int bus_seat_append_can_tty(DBusMessageIter *i, const char *property, void *data) {
+        Seat *s = data;
+        dbus_bool_t b;
+
+        assert(i);
+        assert(property);
+        assert(s);
+
+        b = seat_can_tty(s);
+
+        if (!dbus_message_iter_append_basic(i, DBUS_TYPE_BOOLEAN, &b))
+                return -ENOMEM;
+
+        return 0;
+}
+
+static int bus_seat_append_can_graphical(DBusMessageIter *i, const char *property, void *data) {
+        Seat *s = data;
+        dbus_bool_t b;
+
+        assert(i);
+        assert(property);
+        assert(s);
+
+        b = seat_can_graphical(s);
+
+        if (!dbus_message_iter_append_basic(i, DBUS_TYPE_BOOLEAN, &b))
+                return -ENOMEM;
+
+        return 0;
+}
+
 static int bus_seat_append_idle_hint(DBusMessageIter *i, const char *property, void *data) {
         Seat *s = data;
         dbus_bool_t b;
@@ -210,7 +244,9 @@ static int get_seat_for_path(Manager *m, const char *path, Seat **_s) {
 static const BusProperty bus_login_seat_properties[] = {
         { "Id",                     bus_property_append_string,      "s", offsetof(Seat, id), true },
         { "ActiveSession",          bus_seat_append_active,       "(so)", 0 },
-        { "CanMultiSession",        bus_seat_append_multi_session,   "b", 0 },
+        { "CanMultiSession",        bus_seat_append_can_multi_session, "b", 0 },
+        { "CanTTY",                 bus_seat_append_can_tty,         "b", 0 },
+        { "CanGraphical",           bus_seat_append_can_graphical,   "b", 0 },
         { "Sessions",               bus_seat_append_sessions,    "a(so)", 0 },
         { "IdleHint",               bus_seat_append_idle_hint,       "b", 0 },
         { "IdleSinceHint",          bus_seat_append_idle_hint_since, "t", 0 },

src/login/logind-seat.c

@@ -104,9 +104,13 @@ int seat_save(Seat *s) {
         fprintf(f,
                 "# This is private data. Do not parse.\n"
                 "IS_VTCONSOLE=%i\n"
-                "CAN_MULTI_SESSION=%i\n",
+                "CAN_MULTI_SESSION=%i\n"
+                "CAN_TTY=%i\n"
+                "CAN_GRAPHICAL=%i\n",
                 seat_is_vtconsole(s),
-                seat_can_multi_session(s));
+                seat_can_multi_session(s),
+                seat_can_tty(s),
+                seat_can_graphical(s));
 
         if (s->active) {
                 assert(s->active->user);
@@ -427,6 +431,18 @@ bool seat_can_multi_session(Seat *s) {
         return s->manager->console_active_fd >= 0;
 }
 
+bool seat_can_tty(Seat *s) {
+        assert(s);
+
+        return seat_is_vtconsole(s);
+}
+
+bool seat_can_graphical(Seat *s) {
+        assert(s);
+
+        return !!s->devices;
+}
+
 int seat_get_idle_hint(Seat *s, dual_timestamp *t) {
         Session *session;
         bool idle_hint = true;

src/login/logind-seat.h

@@ -63,6 +63,9 @@ int seat_attach_session(Seat *s, Session *session);
 
 bool seat_is_vtconsole(Seat *s);
 bool seat_can_multi_session(Seat *s);
+bool seat_can_tty(Seat *s);
+bool seat_can_graphical(Seat *s);
+
 int seat_get_idle_hint(Seat *s, dual_timestamp *t);
 
 int seat_start(Seat *s);