fbdev: Handle video= parameter in video/cmdline.c

Handle the command-line parameter video= in video/cmdline.c. Implement
the fbdev helper fb_get_options() on top. Will allows to handle the
kernel parameter in DRM without fbdev dependencies.

Note that __video_get_options() has the meaning of its return value
inverted compared to fb_get_options(). The new helper returns true if
the adapter has been enabled, and false otherwise.

There is the ofonly parameter, which disables output for non-OF-based
framebuffers. It is only for offb and looks like a workaround. The actual
purpose it not clear to me. Use 'video=off' or 'nomodeset' instead.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230209135509.7786-9-tzimmermann@suse.de

1 files changed, 20 insertions, 0 deletions

diff --git a/include/video/cmdline.h b/include/video/cmdline.h
new file mode 100644
index 000000000000..26b80cdaef79
--- /dev/null
+++ b/include/video/cmdline.h
@@ -0,0 +1,20 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef VIDEO_CMDLINE_H
+#define VIDEO_CMDLINE_H
+
+#include <linux/types.h>
+
+#if defined(CONFIG_VIDEO_CMDLINE)
+const char *video_get_options(const char *name);
+
+/* exported for compatibility with fbdev; don't use in new code */
+bool __video_get_options(const char *name, const char **option, bool is_of);
+#else
+static inline const char *video_get_options(const char *name)
+{
+	return NULL;
+}
+#endif
+
+#endif