Allow runtime selection of the lvgl display driver ("backend"), enable DRM backend

CHANGELOG.md

@@ -14,6 +14,8 @@
 - fix: Prevent scrolling when keyboard hides (#21)
 - feat!: Do not show last typed character when typing (#25)
 - feat: Update lvgl & lv_drivers to git master (2022-02-21)
+- feat: allow runtime selection of the lvgl display driver ("backend")
+- feat: allow overriding dpi with the --dpi command line parameter
 
 ## 0.1.0 (2021-11-15)
 

README.md

@@ -1,7 +1,7 @@
 Unl0kr
 ======
 
-Framebuffer-based disk unlocker for the initramfs based on [LVGL].
+Disk unlocker for the initramfs based on [LVGL].
 
 [[_TOC_]]
 
@@ -72,6 +72,7 @@ Mandatory arguments to long options are mandatory for short options too.
                          order.
   -g, --geometry=NxM     Force a display size of N horizontal times M
                          vertical pixels
+  -d  --dpi=N            Overrides the DPI
   -h, --help             Print this message and exit
   -v, --verbose          Enable more detailed logging output on STDERR
   -V, --version          Print the unl0kr version and exit
@@ -89,6 +90,7 @@ For an example configuration file, see [unl0kr.conf].
 - [squeek2lvgl] (git submodule / linked statically)
 - [libinput]
 - [libxkbcommon]
+- [libdrm] (optional, required for the DRM backend)
 - evdev kernel module
 
 ## Building & running
@@ -104,6 +106,28 @@ $ sudo ./_build/unl0kr
 
 With meson <0\.55 use `ninja` instead of `meson compile`\.
 
+### Optional features
+
+If [libdrm] is installed, the DRM backend will be compiled automatically. It's possible to
+change this behaviour using the `with-drm` meson feature. For example,
+
+```
+$ meson _build -Dwith-drm=disabled
+```
+
+will forcibly disable the DRM backend regardless if libdrm is installed or not.
+
+## Backends
+
+Unl0kr supports multiple lvgl display drivers, which are herein referred as "backends".
+
+Currently supported backends:
+
+- fbdev
+- drm (optional)
+
+The backend can be switched at runtime by modifying the `general.backend` configuration.
+
 ## Fonts
 
 In order to work with [LVGL], fonts need to be converted to bitmaps, stored as C arrays. Unl0kr currently uses a combination of the [OpenSans] font for text and the [FontAwesome] font for pictograms. For both fonts only limited character ranges are included to reduce the binary size. To (re)generate the C file containing the combined font, run the following command
@@ -200,6 +224,7 @@ The [FontAwesome] font is licensed under the Open Font License version 1.1.
 [inih]: https://github.com/benhoyt/inih
 [libinput]: https://gitlab.freedesktop.org/libinput/libinput
 [libxkbcommon]: https://github.com/xkbcommon/libxkbcommon
+[libdrm]: https://gitlab.freedesktop.org/mesa/drm
 [lv_drivers]: https://github.com/lvgl/lv_drivers
 [lv_port_linux_frame_buffer]: https://github.com/lvgl/lv_port_linux_frame_buffer
 [lv_sim_emscripten]: https://github.com/lvgl/lv_sim_emscripten/blob/master/mouse_cursor_icon.c

backends.c

@@ -0,0 +1,48 @@
+/**
+ * Copyright 2022 Eugenio Paolantonio (g7)
+ *
+ * This file is part of unl0kr, hereafter referred to as the program.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+#include "backends.h"
+
+#include <string.h>
+
+/**
+ * Public interface
+ */
+
+const char *ul_backends_backends[] = {
+#if USE_FBDEV
+    "fbdev",
+#endif /* USE_FBDEV */
+#if USE_DRM
+    "drm",
+#endif /* USE_DRM */
+    NULL
+};
+
+ul_backends_backend_id_t ul_backends_find_backend_with_name(const char *name) {
+    for (int i = 0; ul_backends_backends[i] != NULL; ++i) {
+        if (strcmp(ul_backends_backends[i], name) == 0) {
+            ul_log(UL_LOG_LEVEL_VERBOSE, "Found backend: %s\n", name);
+            return i;
+        }
+    }
+    ul_log(UL_LOG_LEVEL_WARNING, "Backend %s not found\n", name);
+    return UL_BACKENDS_BACKEND_NONE;
+}

backends.h

@@ -0,0 +1,50 @@
+/**
+ * Copyright 2022 Eugenio Paolantonio (g7)
+ *
+ * This file is part of unl0kr, hereafter referred to as the program.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+#ifndef UL_BACKENDS_H
+#define UL_BACKENDS_H
+
+#include "lv_drv_conf.h"
+
+#include "log.h"
+
+/* NOTE: Only UL_BACKENDS_BACKEND_NONE is ought to have an explicit value assigned */
+typedef enum {
+    UL_BACKENDS_BACKEND_NONE = -1,
+#if USE_FBDEV
+    UL_BACKENDS_BACKEND_FBDEV,
+#endif /* USE_FBDEV */
+#if USE_DRM
+    UL_BACKENDS_BACKEND_DRM,
+#endif /* USE_DRM */
+} ul_backends_backend_id_t;
+
+/* Backends */
+extern const char *ul_backends_backends[];
+
+/**
+ * Find the first backend with a given name.
+ *
+ * @param name backend name
+ * @return ID of the first matching backend or UL_BACKENDS_BACKEND_NONE if no backend matched
+ */
+ul_backends_backend_id_t ul_backends_find_backend_with_name(const char *name);
+
+#endif /* UL_BACKENDS_H */

command_line.c

@@ -82,6 +82,7 @@ static void print_usage() {
         "                         order.\n"
         "  -g, --geometry=NxM     Force a display size of N horizontal times M\n"
         "                         vertical pixels\n"
+        "  -d  --dpi=N            Overrides the DPI\n"
         "  -h, --help             Print this message and exit\n"
         "  -v, --verbose          Enable more detailed logging output on STDERR\n"
         "  -V, --version          Print the unl0kr version and exit\n");
@@ -100,6 +101,7 @@ void ul_cli_parse_opts(int argc, char *argv[], ul_cli_opts *opts) {
         { "config",          required_argument, NULL, 'c' },
         { "config-override", required_argument, NULL, 'C' },
         { "geometry",        required_argument, NULL, 'g' },
+        { "dpi",             required_argument, NULL, 'd' },
         { "help",            no_argument,       NULL, 'h' },
         { "verbose",         no_argument,       NULL, 'v' },
         { "version",         no_argument,       NULL, 'V' },
@@ -108,7 +110,7 @@ void ul_cli_parse_opts(int argc, char *argv[], ul_cli_opts *opts) {
 
     int opt, index = 0;
 
-    while ((opt = getopt_long(argc, argv, "c:C:g:hvV", long_opts, &index)) != -1) {
+    while ((opt = getopt_long(argc, argv, "c:C:g:d:hvV", long_opts, &index)) != -1) {
         switch (opt) {
         case 'c':
             opts->config_files[0] = optarg;
@@ -128,6 +130,12 @@ void ul_cli_parse_opts(int argc, char *argv[], ul_cli_opts *opts) {
                 exit(EXIT_FAILURE);
             }
             break;
+        case 'd':
+            if (sscanf(optarg, "%i", &(opts->dpi)) != 1) {
+                ul_log(UL_LOG_LEVEL_ERROR, "Invalid dpi argument \"%s\"\n", optarg);
+                exit(EXIT_FAILURE);
+            }
+            break;
         case 'h':
             print_usage();
             exit(EXIT_SUCCESS);

command_line.h

@@ -35,6 +35,8 @@ typedef struct {
     int hor_res;
     /* Vertical display resolution */
     int ver_res;
+    /* DPI */
+    int dpi;
     /* Verbose mode. If true, provide more detailed logging output on STDERR. */
     bool verbose;
 } ul_cli_opts;

config.c

@@ -73,6 +73,7 @@ static bool parse_bool(const char *value, bool *result);
 
 static void init_opts(ul_config_opts *opts) {
     opts->general.animations = false;
+    opts->general.backend = ul_backends_backends[0] == NULL ? UL_BACKENDS_BACKEND_NONE : 0;
     opts->keyboard.autohide = true;
     opts->keyboard.layout_id = SQ2LV_LAYOUT_US;
     opts->keyboard.popovers = false;
@@ -95,6 +96,12 @@ static int parsing_handler(void* user_data, const char* section, const char* key
             if (parse_bool(value, &(opts->general.animations))) {
                 return 1;
             }
+        } else if (strcmp(key, "backend") == 0) {
+            ul_backends_backend_id_t id = ul_backends_find_backend_with_name(value);
+            if (id != UL_BACKENDS_BACKEND_NONE) {
+                opts->general.backend = id;
+                return 1;
+            }
         }
     } else if (strcmp(section, "keyboard") == 0) {
         if (strcmp(key, "autohide") == 0) {

config.h

@@ -21,6 +21,8 @@
 #ifndef UL_CONFIG_H
 #define UL_CONFIG_H
 
+#include "backends.h"
+
 #include "themes.h"
 
 #include "sq2lv_layouts.h"
@@ -31,6 +33,8 @@
  * General options
  */
 typedef struct {
+    /* Backend to use */
+    ul_backends_backend_id_t backend;
     /* If true, use animations */
     bool animations;
 } ul_config_opts_general;

main.c

@@ -18,6 +18,7 @@
  */
 
 
+#include "backends.h"
 #include "command_line.h"
 #include "config.h"
 #include "indev.h"
@@ -27,7 +28,14 @@
 #include "theme.h"
 #include "themes.h"
 
+#include "lv_drv_conf.h"
+
+#if USE_FBDEV
 #include "lv_drivers/display/fbdev.h"
+#endif /* USE_FBDEV */
+#if USE_DRM
+#include "lv_drivers/display/drm.h"
+#endif /* USE_DRM */
 
 #include "lvgl/lvgl.h"
 
@@ -338,19 +346,45 @@ int main(int argc, char *argv[]) {
     lv_init();
     lv_log_register_print_cb(ul_log_print_cb);
 
-    /* Initialise framebuffer driver and query display size */
-    fbdev_init();
-    uint32_t hor_res;
-    uint32_t ver_res;
-    fbdev_get_sizes(&hor_res, &ver_res);
+    /* Initialise display driver */
+    static lv_disp_drv_t disp_drv;
+    lv_disp_drv_init(&disp_drv);
 
-    /* Override display size with command line options if necessary */
+    /* Initialise framebuffer driver and query display size */
+    uint32_t hor_res = 0;
+    uint32_t ver_res = 0;
+    uint32_t dpi = 0;
+
+    switch (conf_opts.general.backend) {
+#if USE_FBDEV
+    case UL_BACKENDS_BACKEND_FBDEV:
+        fbdev_init();
+        fbdev_get_sizes(&hor_res, &ver_res);
+        disp_drv.flush_cb = fbdev_flush;
+        break;
+#endif /* USE_FBDEV */
+#if USE_DRM
+    case UL_BACKENDS_BACKEND_DRM:
+        drm_init();
+        drm_get_sizes((lv_coord_t *)&hor_res, (lv_coord_t *)&ver_res, &dpi);
+        disp_drv.flush_cb = drm_flush;
+        break;
+#endif /* USE_DRM */
+    default:
+        ul_log(UL_LOG_LEVEL_ERROR, "Unable to find suitable backend");
+        exit(EXIT_FAILURE);
+    }
+
+    /* Override display parameters with command line options if necessary */
     if (cli_opts.hor_res > 0) {
         hor_res = LV_MIN(hor_res, cli_opts.hor_res);
     }
     if (cli_opts.ver_res > 0) {
         ver_res = LV_MIN(ver_res, cli_opts.ver_res);
     }
+    if (cli_opts.dpi > 0) {
+        dpi = cli_opts.dpi;
+    }
 
     /* Prepare display buffer */
     const size_t buf_size = hor_res * ver_res / 10; /* At least 1/10 of the display size is recommended */
@@ -358,13 +392,12 @@ int main(int argc, char *argv[]) {
     lv_color_t *buf = (lv_color_t *)malloc(buf_size * sizeof(lv_color_t));
     lv_disp_draw_buf_init(&disp_buf, buf, NULL, buf_size);    
 
-    /* Initialise display driver */
-    static lv_disp_drv_t disp_drv;
-    lv_disp_drv_init(&disp_drv);
+
+    /* Register display driver */
     disp_drv.draw_buf = &disp_buf;
-    disp_drv.flush_cb = fbdev_flush;
     disp_drv.hor_res = hor_res;
     disp_drv.ver_res = ver_res;
+    disp_drv.dpi = dpi;
     lv_disp_drv_register(&disp_drv);
 
     /* Connect input devices */

meson.build

@@ -27,6 +27,7 @@ project(
 add_project_arguments('-DUL_VERSION="@0@"'.format(meson.project_version()), language: ['c'])
 
 unl0kr_sources = [
+  'backends.c',
   'command_line.c',
   'config.c',
   'cursor.c',
@@ -37,13 +38,25 @@ unl0kr_sources = [
   'sq2lv_layouts.c',
   'terminal.c',
   'theme.c',
-  'themes.c'
+  'themes.c',
 ]
 
 squeek2lvgl_sources = [
   'squeek2lvgl/sq2lv.c',
 ]
 
+unl0kr_dependencies = [
+  dependency('inih'),
+  dependency('libinput'),
+  dependency('xkbcommon'),
+]
+
+libdrm_dep = dependency('libdrm', required: get_option('with-drm'))
+if libdrm_dep.found()
+  unl0kr_dependencies += [libdrm_dep]
+  add_project_arguments('-DUSE_DRM=1', language: ['c'])
+endif
+
 lvgl_sources = run_command('find-lvgl-sources.sh', 'lvgl', check: true).stdout().strip().split('\n')
 
 lv_drivers_sources = run_command('find-lvgl-sources.sh', 'lv_drivers', check: true).stdout().strip().split('\n')
@@ -54,10 +67,6 @@ executable(
   'unl0kr',
   sources: unl0kr_sources + squeek2lvgl_sources + lvgl_sources + lv_drivers_sources,
   include_directories: ['lvgl', 'lv_drivers'],
-  dependencies: [
-    dependency('inih'),
-    dependency('libinput'),
-    dependency('xkbcommon')
-  ],
+  dependencies: unl0kr_dependencies,
   install: true
 )

meson_options.txt

@@ -0,0 +1 @@
+option('with-drm', type : 'feature', value : 'auto', description : 'Enable DRM backend')

unl0kr.conf

@@ -1,5 +1,6 @@
 [general]
 animations=true
+#backend=fbdev
 
 [keyboard]
 autohide=true