6 #include <linux/console.h>
11  * Printk console printing implementation for consoles which does not depend
14  * The state of the console is maintained in the "nbcon_state" atomic
17  * The console is locked when:
20  *     console. Only higher priority contexts are allowed to take over the
21  *     lock. A value of 0 (NBCON_PRIO_NONE) means the console is not locked.
23  *   - The 'cpu' field denotes on which CPU the console is locked. It is used
35  *   - The 'unsafe' field allows to take over the console in a safe way in the
37  *     shared resources or when the console device is manipulated. It can be
38  *     cleared, for example, after emitting one character when the console
42  *     console in an unsafe state. The console will stay in the unsafe state
47  *   1) Direct acquire when the console is not owned or is owned by a lower
51  *      when the current owner has lower priority and the console is in an
59  *           console.
66  *           console state.
68  *        b) Gives up console ownership by clearing the 'prio' field.
71  *      console is an unsafe state. It is used only in panic() by the final
80  * All operations on @console::nbcon_state are atomic cmpxchg based to
91  *   - Whether to spin-wait if there is already an owner and the console is
107  * nbcon_state_set - Helper function to set the console state
108  * @con:	Console to update
111  * Only to be used when the console is not yet or no longer visible in the
114 static inline void nbcon_state_set(struct console *con, struct nbcon_state *new)  in nbcon_state_set()
120  * nbcon_state_read - Helper function to read the console state
121  * @con:	Console to read
124 static inline void nbcon_state_read(struct console *con, struct nbcon_state *state)  in nbcon_state_read()
130  * nbcon_state_try_cmpxchg() - Helper function for atomic_try_cmpxchg() on console state
131  * @con:	Console to update
137 static inline bool nbcon_state_try_cmpxchg(struct console *con, struct nbcon_state *cur,  in nbcon_state_try_cmpxchg()
162 	 * Having a 32bit representation in the console is sufficient.  in __nbcon_seq_to_seq()
163 	 * If a console ever gets more than 2^31 records behind  in __nbcon_seq_to_seq()
177  * nbcon_seq_read - Read the current console sequence
178  * @con:	Console to read the sequence of
182 u64 nbcon_seq_read(struct console *con)  in nbcon_seq_read()
190  * nbcon_seq_force - Force console sequence to a specific value
191  * @con:	Console to work on
197 void nbcon_seq_force(struct console *con, u64 seq)  in nbcon_seq_force()
214  * nbcon_seq_try_update - Try to update the console sequence number
222  * console. In the later case, it will stop printing anyway.
227 	struct console *con = ctxt->console;  in nbcon_seq_try_update()
240  * @cur:	The current console state
242  * Acquire the console when it is released. Also acquire the console when
243  * the current owner has a lower priority and the console is in a safe state.
255  *	-EBUSY:		The current owner has a lower priority but the console
263 	struct console *con = ctxt->console;  in nbcon_context_try_acquire_direct()
277 		 * The console should never be safe for a direct acquire  in nbcon_context_try_acquire_direct()
319  * @cur:	The current console state
322  * It is called when the console is in an unsafe state. The current
323  * owner will release the console on exit from the unsafe region.
325  * Return:	0 on success and @cur is updated to the new console state.
333  *	-EBUSY:		The console is still locked. The caller should
343 	struct console *con = ctxt->console;  in nbcon_context_try_acquire_requested()
382 	/* Handover success. This context now owns the console. */  in nbcon_context_try_acquire_requested()
389  * @cur:	The current console state
392  * than the current owner and the console is in an unsafe state.
396  * the request. Then it waits until the current owner releases the console,
400  * region and releases the console. It does not touch the "req_prio" field
401  * so that the console stays reserved for the waiter.
410  *			console or the handover request.
414  *			willing to wait (zero timeout). Or the console does
426 	struct console *con = ctxt->console;  in nbcon_context_try_acquire_handover()
443 	 * Console stays unsafe after an unsafe takeover until re-initialized.  in nbcon_context_try_acquire_handover()
455 	 * the console directly when the current state has been modified.  in nbcon_context_try_acquire_handover()
464 	/* Wait until there is no owner and then acquire the console. */  in nbcon_context_try_acquire_handover()
489 		 * the console or the handover request.  in nbcon_context_try_acquire_handover()
519  * @cur:	The current console state
521  * Acquire the console even in the unsafe state.
532 	struct console *con = ctxt->console;  in nbcon_context_try_acquire_hostile()
564  * nbcon_context_try_acquire - Try to acquire nbcon console
567  * Return:	True if the console was acquired. False otherwise.
570  * caller should check the current console state to see if it is
572  * the console is not in an unsafe state.
578 	struct console *con = ctxt->console;  in nbcon_context_try_acquire()
608 	ctxt->seq = nbcon_seq_read(ctxt->console);  in nbcon_context_try_acquire()
634  * nbcon_context_release - Release the console
640 	struct console *con = ctxt->console;  in nbcon_context_release()
667  * @cur:	The current console state
669  * Return:	True if this context still owns the console. False if
677  * It can be called inside an unsafe section when the console is just
686  * the console and is no longer allowed to go forward. In this case it must
694 	/* Make sure this context still owns the console. */  in nbcon_context_can_proceed()
698 	/* The console owner can proceed if there is no waiter. */  in nbcon_context_can_proceed()
703 	 * A console owner within an unsafe region is always allowed to  in nbcon_context_can_proceed()
724 	 * outermost callsite must make the final decision whether console  in nbcon_context_can_proceed()
728 	 * The calling context no longer owns the console so go back all the  in nbcon_context_can_proceed()
739  * Return:	True if this context still owns the console. False if
746  * It can be called inside an unsafe section when the console is just
754  * the console and is no longer allowed to go forward. In this case it must
761 	struct console *con = ctxt->console;  in nbcon_can_proceed()
779  *		owns the console. Otherwise false if ownership was handed
782  * This function allows console owners to modify the unsafe status of the
783  * console.
786  * the console and is no longer allowed to go forward. In this case it must
794 	struct console *con = ctxt->console;  in __nbcon_context_update_unsafe()
824  * Return:	True if this context still owns the console. False if
828  * the console and is no longer allowed to go forward. In this case it must
844  * Return:	True if this context still owns the console. False if
848  * the console and is no longer allowed to go forward. In this case it must
864  * Return:	True if this context still owns the console. False if
868  * the console and is no longer allowed to go forward. In this case it must
871  * wants to do more it must reacquire the console first.
880 	struct console *con = ctxt->console;  in nbcon_emit_next_record()
941 	 * dropped count for the console.  in nbcon_emit_next_record()
965  * nbcon_alloc - Allocate buffers needed by the nbcon console
966  * @con:	Console to allocate buffers for
968  * Return:	True on success. False otherwise and the console cannot
972  * be performed earlier in the console registration process.
974 bool nbcon_alloc(struct console *con)  in nbcon_alloc()
978 		 * Boot console printing is synchronized with legacy console  in nbcon_alloc()
995  * nbcon_init - Initialize the nbcon console specific data
996  * @con:	Console to initialize
1003 void nbcon_init(struct console *con)  in nbcon_init()
1015  * nbcon_free - Free and cleanup the nbcon console specific data
1016  * @con:	Console to free/cleanup nbcon data
1018 void nbcon_free(struct console *con)  in nbcon_free()