sound/pci/emu10k1/timer.c

Source file repositories/reference/linux-study-clean/sound/pci/emu10k1/timer.c

File Facts

System
Linux kernel
Corpus path
sound/pci/emu10k1/timer.c
Extension
.c
Size
2318 bytes
Lines
90
Domain
Driver Families
Bucket
sound/pci
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *  Copyright (c) by Lee Revell <rlrevell@joe-job.com>
 *                   Clemens Ladisch <clemens@ladisch.de>
 *                   Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
 *
 *  Routines for control of EMU10K1 chips
 */

#include <linux/time.h>
#include <sound/core.h>
#include <sound/emu10k1.h>

static int snd_emu10k1_timer_start(struct snd_timer *timer)
{
	struct snd_emu10k1 *emu;
	unsigned int delay;

	emu = snd_timer_chip(timer);
	delay = timer->sticks - 1;
	if (delay < 5 ) /* minimum time is 5 ticks */
		delay = 5;
	snd_emu10k1_intr_enable(emu, INTE_INTERVALTIMERENB);
	outw(delay & TIMER_RATE_MASK, emu->port + TIMER);
	return 0;
}

static int snd_emu10k1_timer_stop(struct snd_timer *timer)
{
	struct snd_emu10k1 *emu;

	emu = snd_timer_chip(timer);
	snd_emu10k1_intr_disable(emu, INTE_INTERVALTIMERENB);
	return 0;
}

static unsigned long snd_emu10k1_timer_c_resolution(struct snd_timer *timer)
{
	struct snd_emu10k1 *emu = snd_timer_chip(timer);

	if (emu->card_capabilities->emu_model &&
	    emu->emu1010.word_clock == 44100)
		return 22676;  // 1 sample @ 44.1 kHz = 22.675736...us
	else
		return 20833;  // 1 sample @ 48 kHz = 20.833...us
}

static int snd_emu10k1_timer_precise_resolution(struct snd_timer *timer,
					       unsigned long *num, unsigned long *den)
{
	struct snd_emu10k1 *emu = snd_timer_chip(timer);

	*num = 1;
	if (emu->card_capabilities->emu_model)
		*den = emu->emu1010.word_clock;
	else
		*den = 48000;
	return 0;
}

static const struct snd_timer_hardware snd_emu10k1_timer_hw = {
	.flags = SNDRV_TIMER_HW_AUTO,
	.ticks = 1024,
	.start = snd_emu10k1_timer_start,
	.stop = snd_emu10k1_timer_stop,
	.c_resolution = snd_emu10k1_timer_c_resolution,
	.precise_resolution = snd_emu10k1_timer_precise_resolution,
};

int snd_emu10k1_timer(struct snd_emu10k1 *emu, int device)
{
	struct snd_timer *timer = NULL;
	struct snd_timer_id tid;
	int err;

	tid.dev_class = SNDRV_TIMER_CLASS_CARD;
	tid.dev_sclass = SNDRV_TIMER_SCLASS_NONE;
	tid.card = emu->card->number;
	tid.device = device;
	tid.subdevice = 0;
	err = snd_timer_new(emu->card, "EMU10K1", &tid, &timer);
	if (err >= 0) {
		strscpy(timer->name, "EMU10K1 timer");
		timer->private_data = emu;
		timer->hw = snd_emu10k1_timer_hw;
	}
	emu->timer = timer;
	return err;
}

Annotation

Implementation Notes