linux-next/kernel/printk/nbcon.c

// SPDX-License-Identifier: GPL-2.0-only
// Copyright (C) 2022 Linutronix GmbH, John Ogness
// Copyright (C) 2022 Intel, Thomas Gleixner

#include <linux/kernel.h>
#include <linux/console.h>
#include "internal.h"
/*
 * Printk console printing implementation for consoles which does not depend
 * on the legacy style console_lock mechanism.
 */

/**
 * nbcon_state_set - Helper function to set the console state
 * @con:	Console to update
 * @new:	The new state to write
 *
 * Only to be used when the console is not yet or no longer visible in the
 * system. Otherwise use nbcon_state_try_cmpxchg().
 */
static inline void nbcon_state_set(struct console *con, struct nbcon_state *new)
{
	atomic_set(&ACCESS_PRIVATE(con, nbcon_state), new->atom);
}

/**
 * nbcon_state_read - Helper function to read the console state
 * @con:	Console to read
 * @state:	The state to store the result
 */
static inline void nbcon_state_read(struct console *con, struct nbcon_state *state)
{
	state->atom = atomic_read(&ACCESS_PRIVATE(con, nbcon_state));
}

/**
 * nbcon_state_try_cmpxchg() - Helper function for atomic_try_cmpxchg() on console state
 * @con:	Console to update
 * @cur:	Old/expected state
 * @new:	New state
 *
 * Return: True on success. False on fail and @cur is updated.
 */
static inline bool nbcon_state_try_cmpxchg(struct console *con, struct nbcon_state *cur,
					   struct nbcon_state *new)
{
	return atomic_try_cmpxchg(&ACCESS_PRIVATE(con, nbcon_state), &cur->atom, new->atom);
}

/**
 * nbcon_init - Initialize the nbcon console specific data
 * @con:	Console to initialize
 */
void nbcon_init(struct console *con)
{
	struct nbcon_state state = { };

	nbcon_state_set(con, &state);
}

/**
 * nbcon_cleanup - Cleanup the nbcon console specific data
 * @con:	Console to cleanup
 */
void nbcon_cleanup(struct console *con)
{
	struct nbcon_state state = { };

	nbcon_state_set(con, &state);
}