seq_fifo.c

  1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 *   ALSA sequencer FIFO
  4 *   Copyright (c) 1998 by Frank van de Pol <fvdpol@coil.demon.nl>
  5 */
  6
  7#include <sound/core.h>
  8#include <linux/slab.h>
  9#include <linux/sched/signal.h>
 10
 11#include "seq_fifo.h"
 12#include "seq_lock.h"
 13
 14
 15/* FIFO */
 16
 17/* create new fifo */
 18struct snd_seq_fifo *snd_seq_fifo_new(int poolsize)
 19{
 20	struct snd_seq_fifo *f;
 21
 22	f = kzalloc(sizeof(*f), GFP_KERNEL);
 23	if (!f)
 24		return NULL;
 25
 26	f->pool = snd_seq_pool_new(poolsize);
 27	if (f->pool == NULL) {
 28		kfree(f);
 29		return NULL;
 30	}
 31	if (snd_seq_pool_init(f->pool) < 0) {
 32		snd_seq_pool_delete(&f->pool);
 33		kfree(f);
 34		return NULL;
 35	}
 36
 37	spin_lock_init(&f->lock);
 38	snd_use_lock_init(&f->use_lock);
 39	init_waitqueue_head(&f->input_sleep);
 40	atomic_set(&f->overflow, 0);
 41
 42	f->head = NULL;
 43	f->tail = NULL;
 44	f->cells = 0;
 45	
 46	return f;
 47}
 48
 49void snd_seq_fifo_delete(struct snd_seq_fifo **fifo)
 50{
 51	struct snd_seq_fifo *f;
 52
 53	if (snd_BUG_ON(!fifo))
 54		return;
 55	f = *fifo;
 56	if (snd_BUG_ON(!f))
 57		return;
 58	*fifo = NULL;
 59
 60	if (f->pool)
 61		snd_seq_pool_mark_closing(f->pool);
 62
 63	snd_seq_fifo_clear(f);
 64
 65	/* wake up clients if any */
 66	if (waitqueue_active(&f->input_sleep))
 67		wake_up(&f->input_sleep);
 68
 69	/* release resources...*/
 70	/*....................*/
 71
 72	if (f->pool) {
 73		snd_seq_pool_done(f->pool);
 74		snd_seq_pool_delete(&f->pool);
 75	}
 76	
 77	kfree(f);
 78}
 79
 80static struct snd_seq_event_cell *fifo_cell_out(struct snd_seq_fifo *f);
 81
 82/* clear queue */
 83void snd_seq_fifo_clear(struct snd_seq_fifo *f)
 84{
 85	struct snd_seq_event_cell *cell;
 86
 87	/* clear overflow flag */
 88	atomic_set(&f->overflow, 0);
 89
 90	snd_use_lock_sync(&f->use_lock);
 91	guard(spinlock_irq)(&f->lock);
 92	/* drain the fifo */
 93	while ((cell = fifo_cell_out(f)) != NULL) {
 94		snd_seq_cell_free(cell);
 95	}
 96}
 97
 98
 99/* enqueue event to fifo */
100int snd_seq_fifo_event_in(struct snd_seq_fifo *f,
101			  struct snd_seq_event *event)
102{
103	struct snd_seq_event_cell *cell;
104	int err;
105
106	if (snd_BUG_ON(!f))
107		return -EINVAL;
108
109	guard(snd_seq_fifo)(f);
110	err = snd_seq_event_dup(f->pool, event, &cell, 1, NULL, NULL); /* always non-blocking */
111	if (err < 0) {
112		if ((err == -ENOMEM) || (err == -EAGAIN))
113			atomic_inc(&f->overflow);
114		return err;
115	}
116		
117	/* append new cells to fifo */
118	scoped_guard(spinlock_irqsave, &f->lock) {
119		if (f->tail != NULL)
120			f->tail->next = cell;
121		f->tail = cell;
122		if (f->head == NULL)
123			f->head = cell;
124		cell->next = NULL;
125		f->cells++;
126	}
127
128	/* wakeup client */
129	if (waitqueue_active(&f->input_sleep))
130		wake_up(&f->input_sleep);
131
132	return 0; /* success */
133
134}
135
136/* dequeue cell from fifo */
137static struct snd_seq_event_cell *fifo_cell_out(struct snd_seq_fifo *f)
138{
139	struct snd_seq_event_cell *cell;
140
141	cell = f->head;
142	if (cell) {
143		f->head = cell->next;
144
145		/* reset tail if this was the last element */
146		if (f->tail == cell)
147			f->tail = NULL;
148
149		cell->next = NULL;
150		f->cells--;
151	}
152
153	return cell;
154}
155
156/* dequeue cell from fifo and copy on user space */
157int snd_seq_fifo_cell_out(struct snd_seq_fifo *f,
158			  struct snd_seq_event_cell **cellp, int nonblock)
159{
160	struct snd_seq_event_cell *cell;
161	unsigned long flags;
162	wait_queue_entry_t wait;
163
164	if (snd_BUG_ON(!f))
165		return -EINVAL;
166
167	*cellp = NULL;
168	init_waitqueue_entry(&wait, current);
169	spin_lock_irqsave(&f->lock, flags);
170	while ((cell = fifo_cell_out(f)) == NULL) {
171		if (nonblock) {
172			/* non-blocking - return immediately */
173			spin_unlock_irqrestore(&f->lock, flags);
174			return -EAGAIN;
175		}
176		set_current_state(TASK_INTERRUPTIBLE);
177		add_wait_queue(&f->input_sleep, &wait);
178		spin_unlock_irqrestore(&f->lock, flags);
179		schedule();
180		spin_lock_irqsave(&f->lock, flags);
181		remove_wait_queue(&f->input_sleep, &wait);
182		if (signal_pending(current)) {
183			spin_unlock_irqrestore(&f->lock, flags);
184			return -ERESTARTSYS;
185		}
186	}
187	spin_unlock_irqrestore(&f->lock, flags);
188	*cellp = cell;
189
190	return 0;
191}
192
193
194void snd_seq_fifo_cell_putback(struct snd_seq_fifo *f,
195			       struct snd_seq_event_cell *cell)
196{
197	if (cell) {
198		guard(spinlock_irqsave)(&f->lock);
199		cell->next = f->head;
200		f->head = cell;
201		if (!f->tail)
202			f->tail = cell;
203		f->cells++;
204	}
205}
206
207
208/* polling; return non-zero if queue is available */
209int snd_seq_fifo_poll_wait(struct snd_seq_fifo *f, struct file *file,
210			   poll_table *wait)
211{
212	poll_wait(file, &f->input_sleep, wait);
213	guard(spinlock_irq)(&f->lock);
214	return (f->cells > 0);
215}
216
217/* change the size of pool; all old events are removed */
218int snd_seq_fifo_resize(struct snd_seq_fifo *f, int poolsize)
219{
220	struct snd_seq_pool *newpool, *oldpool;
221	struct snd_seq_event_cell *cell, *next, *oldhead;
222
223	if (snd_BUG_ON(!f || !f->pool))
224		return -EINVAL;
225
226	/* allocate new pool */
227	newpool = snd_seq_pool_new(poolsize);
228	if (newpool == NULL)
229		return -ENOMEM;
230	if (snd_seq_pool_init(newpool) < 0) {
231		snd_seq_pool_delete(&newpool);
232		return -ENOMEM;
233	}
234
235	scoped_guard(spinlock_irq, &f->lock) {
236		/* remember old pool */
237		oldpool = f->pool;
238		oldhead = f->head;
239		/* exchange pools */
240		f->pool = newpool;
241		f->head = NULL;
242		f->tail = NULL;
243		f->cells = 0;
244		/* NOTE: overflow flag is not cleared */
245	}
246
247	/* close the old pool and wait until all users are gone */
248	snd_seq_pool_mark_closing(oldpool);
249	snd_use_lock_sync(&f->use_lock);
250
251	/* release cells in old pool */
252	for (cell = oldhead; cell; cell = next) {
253		next = cell->next;
254		snd_seq_cell_free(cell);
255	}
256	snd_seq_pool_delete(&oldpool);
257
258	return 0;
259}
260
261/* get the number of unused cells safely */
262int snd_seq_fifo_unused_cells(struct snd_seq_fifo *f)
263{
264	if (!f)
265		return 0;
266
267	guard(snd_seq_fifo)(f);
268	guard(spinlock_irqsave)(&f->lock);
269	return snd_seq_unused_cells(f->pool);
270}