linux_cmdline.c

/*-
 * Copyright (c) 2022 Beckhoff Automation GmbH & Co. KG
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 */

#include <sys/param.h>
#include <sys/systm.h>

#include <video/cmdline.h>

const char *
video_get_options(const char *connector_name)
{
	char tunable[64];
	const char *options;

	/*
	 * A user may use loader tunables to set a specific mode for the
	 * console. Tunables are read in the following order:
	 *     1. kern.vt.fb.modes.$connector_name
	 *     2. kern.vt.fb.default_mode
	 *
	 * Example of a mode specific to the LVDS connector:
	 *     kern.vt.fb.modes.LVDS="1024x768"
	 *
	 * Example of a mode applied to all connectors not having a
	 * connector-specific mode:
	 *     kern.vt.fb.default_mode="640x480"
	 */
	snprintf(tunable, sizeof(tunable), "kern.vt.fb.modes.%s",
	    connector_name);
	if (bootverbose) {
		printf("[drm] Connector %s: get mode from tunables:\n", connector_name);
		printf("[drm]  - %s\n", tunable);
		printf("[drm]  - kern.vt.fb.default_mode\n");
	}
	options = kern_getenv(tunable);
	if (options == NULL)
		options = kern_getenv("kern.vt.fb.default_mode");

	return (options);
}