I add a new device /dev/xen/gntalloc, and try to open /dev/xen/gntalloc in agl-compositor process. But it failed to open the device and the errno is "Permission denied". 

Code: agl/build/tmp/work/aarch64-mx8-agl-linux/agl-compositor/0.0.10+gitAUTOINC+4d3727ec24-ro/git/src/main.c
int main(int argc, char *argv[])
{
struct ivi_compositor ivi =

{ 0 };
struct wl_display *display = NULL;
struct wl_event_loop *loop;
struct wl_event_source *signals[3] = { 0 }

;
struct weston_config_section *section;
/* Command line options */
char *backend = NULL;
char *socket_name = NULL;
char *log = NULL;
int help = 0;
int version = 0;
int no_config = 0;
int debug = 0;
char *config_file = NULL;
struct weston_log_context *log_ctx = NULL;
struct weston_log_subscriber *logger;
int ret = EXIT_FAILURE;
//test
int fd1 = -1;

const struct weston_option core_options[] = {

{ WESTON_OPTION_STRING, "backend", 'B', &backend }

,

{ WESTON_OPTION_STRING, "socket", 'S', &socket_name }

,

{ WESTON_OPTION_STRING, "log", 0, &log }

,

{ WESTON_OPTION_BOOLEAN, "help", 'h', &help }

,

{ WESTON_OPTION_BOOLEAN, "version", 0, &version }

,

{ WESTON_OPTION_BOOLEAN, "no-config", 0, &no_config }

,

{ WESTON_OPTION_BOOLEAN, "debug", 0, &debug }

,

{ WESTON_OPTION_STRING, "config", 'c', &config_file }

,
};

//test
fd1 = open("/dev/xen/gntalloc", O_RDWR);
if ( fd1 == -1 )

{ fprintf(stderr, "~~open gntalloc failed\n"); fprintf(stderr, "~~errno:%s\n", strerror(errno)); }

}
 
Error log:
[03:07:09.903] ~~~open gntalloc failed
[03:07:09.904] ~~~errno:Permission denied
[03:07:09.904] osdep open failed
[03:07:09.904] xengntshr_open() fail

[ 35.662117] audit: type=1400 audit(1593400029.900:5): lsm=SMACK fn=smack_inode_permission action=denied subject="System::Weston" object="_" requested=rw pid=529 comm="agl-compositor" name="gntalloc" dev="devtmpfs" ino=3174

Also, I tried to open the same device in other process like vm-cluster-receiver which started manually, it's successful. I guess I should config device access permission for the process agl-compositor, but I don't know how to do that. Please tell me how. Thanks a lot!

Best regards!