path: root/sound/drivers/pcmtest.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Virtual ALSA driver for PCM testing/fuzzing
 *
 * Copyright 2023 Ivan Orlov <ivan.orlov0322@gmail.com>
 *
 * This is a simple virtual ALSA driver, which can be used for audio applications/PCM middle layer
 * testing or fuzzing.
 * It can:
 *	- Simulate 'playback' and 'capture' actions
 *	- Generate random or pattern-based capture data
 *	- Check playback buffer for containing looped template, and notify about the results
 *	through the debugfs entry
 *	- Inject delays into the playback and capturing processes. See 'inject_delay' parameter.
 *	- Inject errors during the PCM callbacks.
 *	- Register custom RESET ioctl and notify when it is called through the debugfs entry
 *	- Work in interleaved and non-interleaved modes
 *	- Support up to 8 substreams
 *	- Support up to 4 channels
 *	- Support framerates from 8 kHz to 48 kHz
 *
 * When driver works in the capture mode with multiple channels, it duplicates the looped
 * pattern to each separate channel. For example, if we have 2 channels, format = U8, interleaved
 * access mode and pattern 'abacaba', the DMA buffer will look like aabbccaabbaaaa..., so buffer for
 * each channel will contain abacabaabacaba... Same for the non-interleaved mode.
 *
 * However, it may break the capturing on the higher framerates with small period size, so it is
 * better to choose larger period sizes.
 *
 * You can find the corresponding selftest in the 'alsa' selftests folder.
 */

#include <linux/module.h>
#include <linux/init.h>
#include <sound/pcm.h>
#include <sound/core.h>
#include <linux/dma-mapping.h>
#include <linux/platform_device.h>
#include <linux/timer.h>
#include <linux/random.h>
#include <linux/debugfs.h>
#include <linux/delay.h>

#define TIMER_PER_SEC 5
#define TIMER_INTERVAL (HZ / TIMER_PER_SEC)
#define DELAY_JIFFIES HZ
#define PLAYBACK_SUBSTREAM_CNT	8
#define CAPTURE_SUBSTREAM_CNT	8
#define MAX_CHANNELS_NUM	4

#define DEFAULT_PATTERN		"abacaba"
#define DEFAULT_PATTERN_LEN	7

#define FILL_MODE_RAND	0
#define FILL_MODE_PAT	1

#define MAX_PATTERN_LEN 4096

static int index = -1;
static char *id = "pcmtest";
static bool enable = true;
static int inject_delay;
static bool inject_hwpars_err;
static bool inject_prepare_err;
static bool inject_trigger_err;
static bool inject_open_err;

static short fill_mode = FILL_MODE_PAT;

static u8 playback_capture_test;
static u8 ioctl_reset_test;
static struct dentry *driver_debug_dir;

module_param(index, int, 0444);
MODULE_PARM_DESC(index, "Index value for pcmtest soundcard");
module_param(id, charp, 0444);
MODULE_PARM_DESC(id, "ID string for pcmtest soundcard");
module_param(enable, bool, 0444);
MODULE_PARM_DESC(enable, "Enable pcmtest soundcard.");
module_param(fill_mode, short, 0600);
MODULE_PARM_DESC(fill_mode, "Buffer fill mode: rand(0) or pattern(1)");
module_param(inject_delay, int, 0600);
MODULE_PARM_DESC(inject_delay, "Inject delays during playback/capture (in jiffies)");
module_param(inject_hwpars_err, bool, 0600);
MODULE_PARM_DESC(inject_hwpars_err, "Inject EBUSY error in the 'hw_params' callback");
module_param(inject_prepare_err, bool, 0600);
MODULE_PARM_DESC(inject_prepare_err, "Inject EINVAL error in the 'prepare' callback");
module_param(inject_trigger_err, bool, 0600);
MODULE_PARM_DESC(inject_trigger_err, "Inject EINVAL error in the 'trigger' callback");
module_param(inject_open_err, bool, 0600);
MODULE_PARM_DESC(inject_open_err, "Inject EBUSY error in the 'open' callback");

struct pcmtst {
	struct snd_pcm *pcm;
	struct snd_card *card;
	struct platform_device *pdev;
};

struct pcmtst_buf_iter {
	size_t buf_pos;				// position in the DMA buffer
	size_t period_pos;			// period-relative position
	size_t b_rw;				// Bytes to write on every timer tick
	size_t s_rw_ch;				// Samples to write to one channel on every tick
	unsigned int sample_bytes;		// sample_bits / 8
	bool is_buf_corrupted;			// playback test result indicator
	size_t period_bytes;			// bytes in a one period
	bool interleaved;			// Interleaved/Non-interleaved mode
	size_t total_bytes;			// Total bytes read/written
	size_t chan_block;			// Bytes in one channel buffer when non-interleaved
	struct snd_pcm_substream *substream;
	bool suspend;				// We need to pause timer without shutting it down
	struct timer_list timer_instance;
};

static struct snd_pcm_hardware snd_pcmtst_hw = {
	.info = (SNDRV_PCM_INFO_INTERLEAVED |
		 SNDRV_PCM_INFO_BLOCK_TRANSFER |
		 SNDRV_PCM_INFO_NONINTERLEAVED |
		 SNDRV_PCM_INFO_MMAP_VALID |
		 SNDRV_PCM_INFO_PAUSE),
	.formats =		SNDRV_PCM_FMTBIT_U8 | SNDRV_PCM_FMTBIT_S16_LE,
	.rates =		SNDRV_PCM_RATE_8000_48000,
	.rate_min =		8000,
	.rate_max =		48000,
	.channels_min =		1,
	.channels_max =		MAX_CHANNELS_NUM,
	.buffer_bytes_max =	128 * 1024,
	.period_bytes_min =	4096,
	.period_bytes_max =	32768,
	.periods_min =		1,
	.periods_max =		1024,
};

struct pattern_buf {
	char *buf;
	u32 len;
};

static int buf_allocated;
static struct pattern_buf patt_bufs[MAX_CHANNELS_NUM];

static inline void inc_buf_pos(struct pcmtst_buf_iter *v_iter, size_t by, size_t bytes)
{
	v_iter->total_bytes += by;
	v_iter->buf_pos += by;
	if (v_iter->buf_pos >= bytes)
		v_iter->buf_pos %= bytes;
}

/*
 * Position in the DMA buffer when we are in the non-interleaved mode. We increment buf_pos
 * every time we write a byte to any channel, so the position in the current channel buffer is
 * (position in the DMA buffer) / count_of_channels + size_of_channel_buf * current_channel
 */
static inline size_t buf_pos_n(struct pcmtst_buf_iter *v_iter, unsigned int channels,
			       unsigned int chan_num)
{
	return v_iter->buf_pos / channels + v_iter->chan_block * chan_num;
}

/*
 * Get the count of bytes written for the current channel in the interleaved mode.
 * This is (count of samples written for the current channel) * bytes_in_sample +
 * (relative position in the current sample)
 */
static inline size_t ch_pos_i(size_t b_total, unsigned int channels, unsigned int b_sample)
{
	return b_total / channels / b_sample * b_sample + (b_total % b_sample);
}

static void check_buf_block_i(struct pcmtst_buf_iter *v_iter, struct snd_pcm_runtime *runtime)
{
	size_t i;
	short ch_num;
	u8 current_byte;

	for (i = 0; i < v_iter->b_rw; i++) {
		current_byte = runtime->dma_area[v_iter->buf_pos];
		if (!current_byte)
			break;
		ch_num = (v_iter->total_bytes / v_iter->sample_bytes) % runtime->channels;
		if (current_byte != patt_bufs[ch_num].buf[ch_pos_i(v_iter->total_bytes,
								   runtime->channels,
								   v_iter->sample_bytes)
							  % patt_bufs[ch_num].len]) {
			v_iter->is_buf_corrupted = true;
			break;
		}
		inc_buf_pos(v_iter, 1, runtime->dma_bytes);
	}
	// If we broke during the loop, add remaining bytes to the buffer position.
	inc_buf_pos(v_iter, v_iter->b_rw - i, runtime->dma_bytes);
}

static void check_buf_block_ni(struct pcmtst_buf_iter *v_iter, struct snd_pcm_runtime *runtime)
{
	unsigned int channels = runtime->channels;
	size_t i;
	short ch_num;
	u8 current_byte;

	for (i = 0; i < v_iter->b_rw; i++) {
		ch_num = i % channels;
		current_byte = runtime->dma_area[buf_pos_n(v_iter, channels, ch_num)];
		if (!current_byte)
			break;
		if (current_byte != patt_bufs[ch_num].buf[(v_iter->total_bytes / channels)
							  % patt_bufs[ch_num].len]) {
			v_iter->is_buf_corrupted = true;
			break;
		}
		inc_buf_pos(v_iter, 1, runtime->dma_bytes);
	}
	inc_buf_pos(v_iter, v_iter->b_rw - i, runtime->dma_bytes);
}

/*
 * Check one block of the buffer. Here we iterate the buffer until we find '0'. This condition is
 * necessary because we need to detect when the reading/writing ends, so we assume that the pattern
 * doesn't contain zeros.
 */
static void check_buf_block(struct pcmtst_buf_iter *v_iter, struct snd_pcm_runtime *runtime)
{
	if (v_iter->interleaved)
		check_buf_block_i(v_iter, runtime);
	else
		check_buf_block_ni(v_iter, runtime);
}

/*
 * Fill buffer in the non-interleaved mode. The order of samples is C0, ..., C0, C1, ..., C1, C2...
 * The channel buffers lay in the DMA buffer continuously (see default copy
 * handlers in the pcm_lib.c file).
 *
 * Here we increment the DMA buffer position every time we write a byte to any channel 'buffer'.
 * We need this to simulate the correct hardware pointer moving.
 */
static void fill_block_pattern_n(struct pcmtst_buf_iter *v_iter, struct snd_pcm_runtime *runtime)
{
	size_t i;
	unsigned int channels = runtime->channels;
	short ch_num;

	for (i = 0; i < v_iter-&g