Default to first modesettable DRM device

When no DRM device is specified on the command line, try all
available DRM devices until an available modesettable device is
found.

Bug-AGL: SPEC-3815

Change-Id: I72343558fcda755a63aee549767ccc8c00c06724
Signed-off-by: Damian Hobson-Garcia <dhobsong@igel.co.jp>

3 files changed, 30 insertions, 5 deletions

diff --git a/README.md b/README.md
index f9a7650..458cdde 100644
--- a/README.md
+++ b/README.md
@@ -65,8 +65,8 @@ Once installed, running the following command will start the DRM Lease Manager d
 
     drm-lease-manager [<path DRM device>]
 
-If no DRM device is specified, `/dev/dri/card0` will be used.  
-More detailed options can be displayed by specifying the `-h` flag.
+If no DRM device is specified, the first available device capabale of modesetting will
+be used.  More detailed options can be displayed by specifying the `-h` flag.
 
 ### Dynamic lease transfer
 
diff --git a/drm-lease-manager/lease-manager.c b/drm-lease-manager/lease-manager.c
index b339037..291594c 100644
--- a/drm-lease-manager/lease-manager.c
+++ b/drm-lease-manager/lease-manager.c
@@ -515,6 +515,29 @@ err:
 	return NULL;
 }
 
+static struct lm *drm_find_drm_device(const char *device)
+{
+	drmDevicePtr devices[64];
+	int ndevs;
+	struct lm *lm = NULL;
+
+	if (device)
+		return drm_device_get_resources(device);
+
+	ndevs = drmGetDevices2(0, devices, 64);
+
+	for (int i = 0; i < ndevs; i++) {
+		lm = drm_device_get_resources(
+		    devices[i]->nodes[DRM_NODE_PRIMARY]);
+		if (lm)
+			break;
+	}
+
+	drmFreeDevices(devices, ndevs);
+
+	return lm;
+}
+
 static int lm_create_leases(struct lm *lm, int num_leases,
 			    const struct lease_config *configs)
 {
@@ -544,10 +567,12 @@ struct lm *lm_create_with_config(const char *device, int num_leases,
 				 struct lease_config *configs)
 {
 	struct lease_config *default_configs = NULL;
-	struct lm *lm = drm_device_get_resources(device);
+	struct lm *lm = drm_find_drm_device(device);
 
-	if (!lm)
+	if (!lm) {
+		ERROR_LOG("No available DRM device found\n");
 		return NULL;
+	}
 
 	if (configs == NULL || num_leases == 0) {
 		num_leases = create_default_lease_configs(lm, &default_configs);
diff --git a/drm-lease-manager/main.c b/drm-lease-manager/main.c
index ff69e75..b4ad379 100644
--- a/drm-lease-manager/main.c
+++ b/drm-lease-manager/main.c
@@ -48,7 +48,7 @@ const struct option options[] = {
 
 int main(int argc, char **argv)
 {
-	char *device = "/dev/dri/card0";
+	char *device = NULL;
 	char *config_file = "/etc/drm-lease-manager.toml";
 
 	bool debug_log = false;