[add] Add Drm fd support (#501)

* [add] Add "--drm-fd" option to flutter-pi.

This allows to start flutter-pi on a specific DRM fd, instead of letting the tool locking the DRM master.
This can be useful if we have several screens and we want to display the flutter-pi content on a specific one, while not locking others.

This works well with the drm-lease-manager project (https://github.com/AGLExport/drm-lease-manager/tree/master)

* [update] Update README.md

---------

Co-authored-by: Renaud Barrau <[email protected]>

Author: Renaud-Barrau

README.md

@@ -381,6 +381,7 @@ OPTIONS:
                              without a display attached.
   --dummy-display-size "width,height" The width & height of the dummy display
                              in pixels.
+  --drm-fd <fd>              An opened and valid DRM file descriptor
 
   -h, --help                 Show this help and exit.
 

src/flutter-pi.c

@@ -141,6 +141,8 @@ OPTIONS:\n\
                              without a display attached.\n\
   --dummy-display-size \"width,height\" The width & height of the dummy display\n\
                              in pixels.\n\
+\n\
+  --drm-fd                   An opened and valid DRM file descriptor\n\
 \n\
   -h, --help                 Show this help and exit.\n\
 \n\
@@ -1876,24 +1878,26 @@ bool flutterpi_parse_cmdline_args(int argc, char **argv, struct flutterpi_cmdlin
         { "videomode", required_argument, NULL, 'v' },
         { "dummy-display", no_argument, &dummy_display_int, 1 },
         { "dummy-display-size", required_argument, NULL, 's' },
+        { "drm-fd", required_argument, NULL, 'f' },
         { 0, 0, 0, 0 },
     };
-
     memset(result_out, 0, sizeof *result_out);
 
     result_out->has_orientation = false;
     result_out->has_rotation = false;
     result_out->has_physical_dimensions = false;
     result_out->has_pixel_format = false;
     result_out->has_runtime_mode = false;
+    result_out->has_drm_fd = false;
     result_out->bundle_path = NULL;
     result_out->engine_argc = 0;
     result_out->engine_argv = NULL;
+    result_out->drm_fd = -1;
 
     finished_parsing_options = false;
     while (!finished_parsing_options) {
         longopt_index = 0;
-        opt = getopt_long(argc, argv, "+i:o:r:d:h", long_options, &longopt_index);
+        opt = getopt_long(argc, argv, "+i:o:r:d:h:f", long_options, &longopt_index);
 
         switch (opt) {
             case 0:
@@ -1997,6 +2001,17 @@ bool flutterpi_parse_cmdline_args(int argc, char **argv, struct flutterpi_cmdlin
 
                 break;
 
+            case 'f':;  // --drm-fd
+                char *drm_fd = strdup(optarg);
+                int fd = atoi(drm_fd);
+                if(fd <= 0){
+                    LOG_ERROR("ERROR: Invalid argument for --drm-fd passed.\n");
+                    return false;
+                }
+                result_out->has_drm_fd = true;
+                result_out->drm_fd = fd;
+                break;
+
             case 'h': printf("%s", usage); return false;
 
             case '?':
@@ -2448,7 +2463,13 @@ struct flutterpi *flutterpi_new_from_args(int argc, char **argv) {
             goto fail_destroy_locales;
         }
     } else {
-        drmdev = find_drmdev(libseat);
+        if(cmd_args.has_drm_fd){
+            /* --drm-fd is passed, we don't want flutter-pi to handle the DRM choice */
+            drmdev = drmdev_new_from_interface_fd(cmd_args.drm_fd, NULL, &drmdev_interface, libseat);
+        }
+        else{
+            drmdev = find_drmdev(libseat);
+        }
         if (drmdev == NULL) {
             goto fail_destroy_locales;
         }

src/flutter-pi.h

@@ -141,6 +141,9 @@ struct flutterpi_cmdline_args {
 
     bool dummy_display;
     struct vec2i dummy_display_size;
+
+    bool has_drm_fd;
+    int drm_fd;
 };
 
 int flutterpi_fill_view_properties(bool has_orientation, enum device_orientation orientation, bool has_rotation, int rotation);