/* * ALSA timer back-end using hrtimer * Copyright (C) 2008 Takashi Iwai * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA * */ #include #include #include #include #include #include #include MODULE_AUTHOR("Takashi Iwai "); MODULE_DESCRIPTION("ALSA hrtimer backend"); MODULE_LICENSE("GPL"); MODULE_ALIAS("snd-timer-" __stringify(SNDRV_TIMER_GLOBAL_HRTIMER)); #define NANO_SEC 1000000000UL /* 10^9 in sec */ static unsigned int resolution; struct snd_hrtimer { struct snd_timer *timer; struct hrtimer hrt; bool in_callback; }; static enum hrtimer_restart snd_hrtimer_callback(struct hrtimer *hrt) { struct snd_hrtimer *stime = container_of(hrt, struct snd_hrtimer, hrt); struct snd_timer *t = stime->timer; ktime_t delta; unsigned long ticks; enum hrtimer_restart ret = HRTIMER_NORESTART; spin_lock(&t->lock); if (!t->running) goto out; /* fast path */ stime->in_callback = true; ticks = t->sticks; spin_unlock(&t->lock); /* calculate the drift */ delta = ktime_sub(hrt->base->get_time(), hrtimer_get_expires(hrt)); if (delta > 0) ticks += ktime_divns(delta, ticks * resolution); snd_timer_interrupt(stime->timer, ticks); spin_lock(&t->lock); if (t->running) { hrtimer_add_expires_ns(hrt, t->sticks * resolution); ret = HRTIMER_RESTART; } stime->in_callback = false; out: spin_unlock(&t->lock); return ret; } static int snd_hrtimer_open(struct snd_timer *t) { struct snd_hrtimer *stime; stime = kzalloc(sizeof(*stime), GFP_KERNEL); if (!stime) return -ENOMEM; hrtimer_init(&stime->hrt, CLOCK_MONOTONIC, HRTIMER_MODE_REL); stime->timer = t; stime->hrt.function = snd_hrtimer_callback; t->private_data = stime; return 0; } static int snd_hrtimer_close(struct snd_timer *t) { struct snd_hrtimer *stime = t->private_data; if (stime) { spin_lock_irq(&t->lock); t->running = 0; /* just to be sure */ stime->in_callback = 1; /* skip start/stop */ spin_unlock_irq(&t->lock); hrtimer_cancel(&stime->hrt); kfree(stime); t->private_data = NULL; } return 0; } static int snd_hrtimer_start(struct snd_timer *t) { struct snd_hrtimer *stime = t->private_data; if (stime->in_callback) return 0; hrtimer_start(&stime->hrt, ns_to_ktime(t->sticks * resolution), HRTIMER_MODE_REL); return 0; } static int snd_hrtimer_stop(struct snd_timer *t) { struct snd_hrtimer *stime = t->private_data; if (stime->in_callback) return 0; hrtimer_try_to_cancel(&stime->hrt); return 0; } static struct snd_timer_hardware hrtimer_hw = { .flags = SNDRV_TIMER_HW_AUTO | SNDRV_TIMER_HW_TASKLET, .open = snd_hrtimer_open, .close = snd_hrtimer_close, .start = snd_hrtimer_start, .stop = snd_hrtimer_stop, }; /* * entry functions */ static struct snd_timer *mytimer; static int __init snd_hrtimer_init(void) { struct snd_timer *timer; int err; resolution = hrtimer_resolution; /* Create a new timer and set up the fields */ err = snd_timer_global_new("hrtimer", SNDRV_TIMER_GLOBAL_HRTIMER, &timer); if (err < 0) return err; timer->module = THIS_MODULE; strcpy(timer->name, "HR timer"); timer->hw = hrtimer_hw; timer->hw.resolution = resolution; timer->hw.ticks = NANO_SEC / resolution; err = snd_timer_global_register(timer); if (err < 0) { snd_timer_global_free(timer); return err; } mytimer = timer; /* remember this */ return 0; } static void __exit snd_hrtimer_exit(void) { if (mytimer) { snd_timer_global_free(mytimer); mytimer = NULL; } } module_init(snd_hrtimer_init); module_exit(snd_hrtimer_exit); on value='7'>7space:mode:
Diffstat (limited to 'drivers/usb/serial/belkin_sa.c')