package/seatd: fix uclibc build

Fix uclibc build which is broken since addition of the package in commit
daae31149017cbf8b03634cfc56da132f7e1ad83

We backport an upstream feature patch, because it includes the actual
fix as a side-effect (including stdarg.h at the proper location).

Fixes:
 - http://autobuild.buildroot.org/results/ad5020c5c1a7730f1ae82bf8215ed63df83421fe

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/seatd/0002-Add-no-op-session.patch

@@ -0,0 +1,223 @@
+From 9a7824b7c3ff5c957632671e91454fc84fbcdda8 Mon Sep 17 00:00:00 2001
+From: Simon Ser <contact@emersion.fr>
+Date: Fri, 26 Mar 2021 10:05:12 +0100
+Subject: [PATCH] Add no-op session
+
+This is useful for headless testing, for instance with VKMS:
+
+    modprobe vkms
+    export WLR_DRM_DEVICES=/dev/dri/card1
+    export WLR_BACKENDS=drm
+    export LIBSEAT_BACKEND=noop
+    sway
+
+We don't need any of the VT handling in this case.
+
+[Retrieved from:
+https://github.com/kennylevinsen/seatd/commit/9a7824b7c3ff5c957632671e91454fc84fbcdda8]
+Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
+---
+ include/libseat.h      |   2 +
+ libseat/backend/noop.c | 135 +++++++++++++++++++++++++++++++++++++++++
+ libseat/libseat.c      |   5 ++
+ meson.build            |   2 +-
+ 4 files changed, 143 insertions(+), 1 deletion(-)
+ create mode 100644 libseat/backend/noop.c
+
+diff --git a/include/libseat.h b/include/libseat.h
+index 5375cd6..82098ea 100644
+--- a/include/libseat.h
++++ b/include/libseat.h
+@@ -1,6 +1,8 @@
+ #ifndef _LIBSEAT_H
+ #define _LIBSEAT_H
+ 
++#include <stdarg.h>
++
+ /*
+  * An opaque struct containing an opened seat, created by libseat_open_seat and
+  * destroyed by libseat_close_seat.
+diff --git a/libseat/backend/noop.c b/libseat/backend/noop.c
+new file mode 100644
+index 0000000..71d0224
+--- /dev/null
++++ b/libseat/backend/noop.c
+@@ -0,0 +1,135 @@
++#include <assert.h>
++#include <errno.h>
++#include <fcntl.h>
++#include <poll.h>
++#include <stdbool.h>
++#include <stdlib.h>
++#include <string.h>
++#include <sys/socket.h>
++#include <unistd.h>
++
++#include "backend.h"
++#include "log.h"
++
++struct backend_noop {
++	struct libseat base;
++	struct libseat_seat_listener *seat_listener;
++	void *seat_listener_data;
++
++	bool initial_setup;
++	int sockets[2];
++};
++
++extern const struct seat_impl noop_impl;
++
++static struct backend_noop *backend_noop_from_libseat_backend(struct libseat *base) {
++	assert(base->impl == &noop_impl);
++	return (struct backend_noop *)base;
++}
++
++static void destroy(struct backend_noop *backend) {
++	close(backend->sockets[0]);
++	close(backend->sockets[1]);
++	free(backend);
++}
++
++static int close_seat(struct libseat *base) {
++	struct backend_noop *backend = backend_noop_from_libseat_backend(base);
++	destroy(backend);
++	return 0;
++}
++
++static int disable_seat(struct libseat *base) {
++	(void)base;
++	return 0;
++}
++
++static const char *seat_name(struct libseat *base) {
++	(void)base;
++	return "noop";
++}
++
++static int open_device(struct libseat *base, const char *path, int *fd) {
++	(void)base;
++
++	int tmpfd = open(path, O_RDWR | O_CLOEXEC);
++	if (tmpfd < 0) {
++		log_errorf("Failed to open device: %s", strerror(errno));
++		return -1;
++	}
++
++	*fd = tmpfd;
++	return tmpfd;
++}
++
++static int close_device(struct libseat *base, int device_id) {
++	(void)base;
++	(void)device_id;
++	return 0;
++}
++
++static int switch_session(struct libseat *base, int s) {
++	(void)base;
++	(void)s;
++	log_errorf("No-op backend cannot switch to session %d", s);
++	return -1;
++}
++
++static int get_fd(struct libseat *base) {
++	struct backend_noop *backend = backend_noop_from_libseat_backend(base);
++	return backend->sockets[0];
++}
++
++static int dispatch_background(struct libseat *base, int timeout) {
++	struct backend_noop *backend = backend_noop_from_libseat_backend(base);
++
++	if (backend->initial_setup) {
++		backend->initial_setup = false;
++		backend->seat_listener->enable_seat(&backend->base, backend->seat_listener_data);
++	}
++
++	struct pollfd fd = {
++		.fd = backend->sockets[0],
++		.events = POLLIN,
++	};
++	if (poll(&fd, 1, timeout) < 0) {
++		if (errno == EAGAIN || errno == EINTR) {
++			return 0;
++		} else {
++			return -1;
++		}
++	}
++
++	return 0;
++}
++
++static struct libseat *noop_open_seat(struct libseat_seat_listener *listener, void *data) {
++	struct backend_noop *backend = calloc(1, sizeof(struct backend_noop));
++	if (backend == NULL) {
++		return NULL;
++	}
++
++	if (socketpair(AF_UNIX, SOCK_STREAM, 0, backend->sockets) != 0) {
++		log_errorf("socketpair() failed: %s", strerror(errno));
++		free(backend);
++		return NULL;
++	}
++
++	backend->seat_listener = listener;
++	backend->seat_listener_data = data;
++	backend->base.impl = &noop_impl;
++
++	return &backend->base;
++}
++
++const struct seat_impl noop_impl = {
++	.open_seat = noop_open_seat,
++	.disable_seat = disable_seat,
++	.close_seat = close_seat,
++	.seat_name = seat_name,
++	.open_device = open_device,
++	.close_device = close_device,
++	.switch_session = switch_session,
++	.get_fd = get_fd,
++	.dispatch = dispatch_background,
++};
+diff --git a/libseat/libseat.c b/libseat/libseat.c
+index b1e8bb2..a7e079c 100644
+--- a/libseat/libseat.c
++++ b/libseat/libseat.c
+@@ -13,6 +13,7 @@
+ extern const struct seat_impl seatd_impl;
+ extern const struct seat_impl logind_impl;
+ extern const struct seat_impl builtin_impl;
++extern const struct seat_impl noop_impl;
+ 
+ static const struct named_backend impls[] = {
+ #ifdef SEATD_ENABLED
+@@ -24,6 +25,7 @@ static const struct named_backend impls[] = {
+ #ifdef BUILTIN_ENABLED
+ 	{"builtin", &builtin_impl},
+ #endif
++	{"noop", &noop_impl},
+ 	{NULL, NULL},
+ };
+ 
+@@ -62,6 +64,9 @@ struct libseat *libseat_open_seat(struct libseat_seat_listener *listener, void *
+ 
+ 	struct libseat *backend = NULL;
+ 	for (const struct named_backend *iter = impls; iter->backend != NULL; iter++) {
++		if (iter->backend == &noop_impl) {
++			continue;
++		}
+ 		backend = iter->backend->open_seat(listener, data);
+ 		if (backend != NULL) {
+ 			log_infof("Seat opened with backend '%s'", iter->name);
+diff --git a/meson.build b/meson.build
+index f41b621..c3800ae 100644
+--- a/meson.build
++++ b/meson.build
+@@ -145,7 +145,7 @@ symbols_file = 'libseat/libseat.syms'
+ symbols_flag = '-Wl,--version-script,@0@/@1@'.format(meson.current_source_dir(), symbols_file)
+ lib = library(
+ 	'seat', # This results in the library being called 'libseat'
+-	[ 'libseat/libseat.c' ],
++	[ 'libseat/libseat.c', 'libseat/backend/noop.c' ],
+ 	soversion: libseat_soversion,
+ 	link_with: private_lib,
+ 	include_directories: [include_directories('.', 'include')],