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walnux/drivers/i2s/i2schar.c
Tiago Medicci Serrano 585c25bac0 drivers/i2s/i2schar: Implement blocking read/write operations 
This commit implements simple (blocking) read and write operations
for the i2schar driver. Although it already contained such methods,
the read/write operation was not being properly handled by the
`i2schar_[rx|tx]callback` (called when the operation has finished).
A semaphore is used to ensure that read data was received by the
receiver and another semaphore ensures that data was written by the
transmitter.

Please note that the already-existing mutex for the I2S peripheral
was replaced by two mutexes, one for the receiver and other for the
transmitter to allow full-duplex communication.

Signed-off-by: Tiago Medicci Serrano <tiago.medicci@espressif.com>
2025-08-27 11:07:05 +08:00

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/****************************************************************************
* drivers/i2s/i2schar.c
*
* SPDX-License-Identifier: Apache-2.0
*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership. The
* ASF licenses this file to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance with the
* License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*
****************************************************************************/
/****************************************************************************
*
* This is a simple character driver for testing I2C. It is not an audio
* driver but does conform to some of the buffer management heuristics of an
* audio driver. It is not suitable for use in any real driver application
* in its current form.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdint.h>
#include <stdio.h>
#include <fcntl.h>
#include <string.h>
#include <assert.h>
#include <debug.h>
#include <errno.h>
#include <semaphore.h>
#include <nuttx/mutex.h>
#include <nuttx/kmalloc.h>
#include <nuttx/fs/fs.h>
#include <nuttx/audio/audio.h>
#include <nuttx/audio/i2s.h>
/****************************************************************************
* Pre-processor Definitions
****************************************************************************/
/* Configuration ************************************************************/
#ifndef CONFIG_AUDIO_I2SCHAR_RXTIMEOUT
# define CONFIG_AUDIO_I2SCHAR_RXTIMEOUT 0
#endif
#ifndef CONFIG_AUDIO_I2SCHAR_TXTIMEOUT
# define CONFIG_AUDIO_I2SCHAR_TXTIMEOUT 0
#endif
/* Device naming ************************************************************/
#define DEVNAME_FMT "/dev/i2schar%d"
#define DEVNAME_FMTLEN (12 + 3 + 1)
/****************************************************************************
* Private Types
****************************************************************************/
struct i2schar_dev_s
{
FAR struct i2s_dev_s *i2s; /* The lower half i2s driver */
mutex_t rx_lock; /* Assures mutually exclusive access to RX operations */
mutex_t tx_lock; /* Assures mutually exclusive access to TX operations */
sem_t rx_sem; /* Semaphore for blocking read operations */
sem_t tx_sem; /* Semaphore for blocking write operations */
int rx_result; /* Result of the last read operation */
int tx_result; /* Result of the last write operation */
};
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/* I2S callback function */
static void i2schar_rxcallback(FAR struct i2s_dev_s *dev,
FAR struct ap_buffer_s *apb,
FAR void *arg,
int result);
static void i2schar_txcallback(FAR struct i2s_dev_s *dev,
FAR struct ap_buffer_s *apb,
FAR void *arg,
int result);
/* Character driver methods */
static ssize_t i2schar_read(FAR struct file *filep, FAR char *buffer,
size_t buflen);
static ssize_t i2schar_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen);
static int i2schar_ioctl(FAR struct file *filep, int cmd, unsigned long arg);
/****************************************************************************
* Private Data
****************************************************************************/
static const struct file_operations g_i2schar_fops =
{
NULL, /* open */
NULL, /* close */
i2schar_read, /* read */
i2schar_write, /* write */
NULL, /* seek */
i2schar_ioctl, /* ioctl */
};
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: i2schar_rxcallback
*
* Description:
* Callback function invoked upon completion of an I2S RX (receive)
* transfer. This function is called by the lower-half I2S driver when
* the reception of an audio buffer is complete.
*
* In this test driver implementation, the received buffer is simply
* freed. This is acceptable if this driver has the sole reference to the
* buffer; in that case, the buffer will be freed. Otherwise, this may
* result in a memory leak. A more efficient design would recycle the
* audio buffers for future use.
*
* In a real application, the received data would typically be returned
* to the caller or passed to another subsystem via IPC or a queue.
*
* Input Parameters:
* dev - Pointer to the I2S device structure
* apb - Pointer to the audio buffer structure that was received
* arg - Pointer to the private data structure (i2schar_dev_s)
* result - The result of the transfer (OK on success, negated errno on
* failure)
*
* Returned Value:
* None
*
****************************************************************************/
static void i2schar_rxcallback(FAR struct i2s_dev_s *dev,
FAR struct ap_buffer_s *apb,
FAR void *arg, int result)
{
FAR struct i2schar_dev_s *priv = (FAR struct i2schar_dev_s *)arg;
DEBUGASSERT(priv != NULL && apb != NULL);
i2sinfo("apb=%p nbytes=%d result=%d\n", apb, apb->nbytes, result);
/* Store the result and signal completion */
priv->rx_result = result;
/* Signal that the read operation has completed */
nxsem_post(&priv->rx_sem);
/* REVISIT: If you want this to actually do something other than
* test I2S data transfer, then this is the point where you would
* want to pass the received I2S to some application.
*/
/* Release our reference to the audio buffer. Hopefully it will be freed
* now.
*/
i2sinfo("Freeing apb=%p crefs=%d\n", apb, apb->crefs);
apb_free(apb);
}
/****************************************************************************
* Name: i2schar_txcallback
*
* Description:
* Callback function invoked upon completion of an I2S TX (transmit)
* transfer. This function is called by the lower-half I2S driver when
* the transmission of an audio buffer is complete.
*
* In this test driver implementation, the transmitted buffer is simply
* freed. This is acceptable if this driver has the sole reference to the
* buffer; in that case, the buffer will be freed. Otherwise, this may
* result in a memory leak. A more efficient design would recycle the
* audio buffers for future use.
*
* Input Parameters:
* dev - Pointer to the I2S device structure
* apb - Pointer to the audio buffer structure that was transmitted
* arg - Pointer to the private data structure (i2schar_dev_s)
* result - The result of the transfer (OK on success, negated errno on
* failure)
*
* Returned Value:
* None
*
****************************************************************************/
static void i2schar_txcallback(FAR struct i2s_dev_s *dev,
FAR struct ap_buffer_s *apb,
FAR void *arg, int result)
{
FAR struct i2schar_dev_s *priv = (FAR struct i2schar_dev_s *)arg;
DEBUGASSERT(priv != NULL && apb != NULL);
i2sinfo("apb=%p nbytes=%d result=%d\n", apb, apb->nbytes, result);
/* Store the result and signal completion */
priv->tx_result = result;
/* Signal that the write operation has completed */
nxsem_post(&priv->tx_sem);
/* REVISIT: If you want this to actually do something other than
* test I2S data transfer, then this is the point where you would
* want to let some application know that the transfer has completed.
*/
/* Release our reference to the audio buffer. Hopefully it will be freed
* now.
*/
i2sinfo("Freeing apb=%p crefs=%d\n", apb, apb->crefs);
apb_free(apb);
}
/****************************************************************************
* Name: i2schar_read
*
* Description:
* Standard character driver read method. This function reads audio data
* from the I2S character device. The data is expected to be provided in
* the form of a single, correctly sized audio buffer (struct ap_buffer_s
* followed by audio data). The function adds a reference to the buffer,
* passes it to the lower-half I2S driver for reception, and waits for the
* transfer to complete via a callback. Upon completion, the function
* returns the number of bytes read or a negated errno value on failure.
*
* Input Parameters:
* filep - Pointer to the file structure instance
* buffer - Pointer to the buffer where the received audio data will be
* stored. This must point to a struct ap_buffer_s followed by
* sufficient space for the audio data.
* buflen - The length of the buffer in bytes. Must be at least the size of
* struct ap_buffer_s plus the number of audio data bytes.
*
* Returned Value:
* On success, returns the number of bytes read (including the
* struct ap_buffer_s header and the audio data). On failure, returns
* a negated errno value indicating the error.
*
****************************************************************************/
static ssize_t i2schar_read(FAR struct file *filep, FAR char *buffer,
size_t buflen)
{
FAR struct inode *inode;
FAR struct i2schar_dev_s *priv;
FAR struct ap_buffer_s *apb;
size_t nbytes;
int ret;
i2sinfo("buffer=%p buflen=%d\n", buffer, (int)buflen);
/* Get our private data structure */
DEBUGASSERT(buffer != NULL);
inode = filep->f_inode;
priv = inode->i_private;
DEBUGASSERT(priv != NULL);
/* Verify that the buffer refers to one, correctly sized audio buffer */
DEBUGASSERT(buflen >= sizeof(struct ap_buffer_s));
apb = (FAR struct ap_buffer_s *)buffer;
nbytes = apb->nmaxbytes;
DEBUGASSERT(buflen >= (sizeof(struct ap_buffer_s) + nbytes));
/* Add a reference to the audio buffer */
apb_reference(apb);
/* Get exclusive access to i2c character driver */
ret = nxmutex_lock(&priv->rx_lock);
if (ret < 0)
{
i2serr("ERROR: nxsem_wait returned: %d\n", ret);
goto errout_with_reference;
}
/* Give the buffer to the I2S driver */
ret = I2S_RECEIVE(priv->i2s, apb, i2schar_rxcallback, priv,
CONFIG_AUDIO_I2SCHAR_RXTIMEOUT);
if (ret < 0)
{
i2serr("ERROR: I2S_RECEIVE returned: %d\n", ret);
goto errout_with_reference;
}
/* Wait for the RX callback to signal completion */
ret = nxsem_wait(&priv->rx_sem);
if (ret < 0)
{
i2serr("ERROR: nxsem_wait returned: %d\n", ret);
goto errout_with_reference;
}
/* Get the result from the private data */
ret = priv->rx_result;
/* If the operation was successful, return the number of bytes received */
if (ret >= 0)
{
ret = sizeof(struct ap_buffer_s) + apb->nbytes;
}
/* Release our reference to the audio buffer */
nxmutex_unlock(&priv->rx_lock);
return ret;
errout_with_reference:
apb_free(apb);
nxmutex_unlock(&priv->rx_lock);
return ret;
}
/****************************************************************************
* Name: i2schar_write
*
* Description:
* Standard character driver write method. This function writes audio data
* to the I2S character device. The data must be provided in the form of a
* single, correctly sized audio buffer (struct ap_buffer_s followed by
* audio data). The function adds a reference to the buffer, sends it to
* the lower-half I2S driver for transmission, and waits for the transfer
* to complete via a callback. Upon completion, the function returns the
* number of bytes written or a negated errno value on failure.
*
* Input Parameters:
* filep - Pointer to the file structure instance
* buffer - Pointer to the buffer containing the audio data to be written.
* This must point to a struct ap_buffer_s followed by the audio
* data.
* buflen - The length of the buffer in bytes. Must be at least the size of
* struct ap_buffer_s plus the number of audio data bytes.
*
* Returned Value:
* On success, returns the number of bytes written (including the
* struct ap_buffer_s header and the audio data). On failure, returns
* a negated errno value indicating the error.
*
****************************************************************************/
static ssize_t i2schar_write(FAR struct file *filep, FAR const char *buffer,
size_t buflen)
{
FAR struct inode *inode;
FAR struct i2schar_dev_s *priv;
FAR struct ap_buffer_s *apb;
size_t nbytes;
int ret;
i2sinfo("buffer=%p buflen=%d\n", buffer, (int)buflen);
/* Get our private data structure */
DEBUGASSERT(buffer);
inode = filep->f_inode;
priv = inode->i_private;
DEBUGASSERT(priv);
/* Verify that the buffer refers to one, correctly sized audio buffer */
DEBUGASSERT(buflen >= sizeof(struct ap_buffer_s));
apb = (FAR struct ap_buffer_s *)buffer;
nbytes = apb->nmaxbytes;
DEBUGASSERT(buflen >= (sizeof(struct ap_buffer_s) + nbytes));
/* Add a reference to the audio buffer */
apb_reference(apb);
/* Get exclusive access to i2c character driver */
ret = nxmutex_lock(&priv->tx_lock);
if (ret < 0)
{
i2serr("ERROR: nxsem_wait returned: %d\n", ret);
goto errout_with_reference;
}
/* Give the audio buffer to the I2S driver */
ret = I2S_SEND(priv->i2s, apb, i2schar_txcallback, priv,
CONFIG_AUDIO_I2SCHAR_TXTIMEOUT);
if (ret < 0)
{
i2serr("ERROR: I2S_SEND returned: %d\n", ret);
goto errout_with_reference;
}
/* Wait for the TX callback to signal completion */
ret = nxsem_wait(&priv->tx_sem);
if (ret < 0)
{
i2serr("ERROR: nxsem_wait returned: %d\n", ret);
goto errout_with_reference;
}
/* Get the result from the private data */
ret = priv->tx_result;
/* If the operation was successful, return the number of bytes sent */
if (ret >= 0)
{
ret = sizeof(struct ap_buffer_s) + apb->nbytes;
}
/* Release our reference to the audio buffer */
nxmutex_unlock(&priv->tx_lock);
return ret;
errout_with_reference:
apb_free(apb);
nxmutex_unlock(&priv->tx_lock);
return ret;
}
/****************************************************************************
* Name: i2schar_ioctl
*
* Description:
* Perform device-specific operations on the I2S character device via ioctl
* commands. This function handles a set of standard I2S ioctl commands for
* getting and setting data width, channel count, and sample rate for both
* RX and TX directions. If the command is not recognized, it is forwarded
* to the lower-half I2S driver's i2s_ioctl method if available.
*
* Input Parameters:
* filep - Pointer to the file structure instance
* cmd - The ioctl command to be performed
* arg - The argument accompanying the ioctl command (may be a pointer or
* a value, depending on the command)
*
* Returned Value:
* Returns zero (OK) on success; a negated errno value on failure.
* If the command is not supported, returns -ENOTTY.
*
****************************************************************************/
static int i2schar_ioctl(FAR struct file *filep, int cmd, unsigned long arg)
{
FAR struct inode *inode;
FAR struct i2schar_dev_s *priv;
int ret = OK;
/* Get our private data structure */
inode = filep->f_inode;
priv = inode->i_private;
DEBUGASSERT(priv != NULL && priv->i2s && priv->i2s->ops);
switch (cmd)
{
case I2SIOC_GRXDATAWIDTH:
{
*(FAR uint32_t *)arg = I2S_RXDATAWIDTH(priv->i2s, 0);
break;
}
case I2SIOC_GTXDATAWIDTH:
{
*(FAR uint32_t *)arg = I2S_TXDATAWIDTH(priv->i2s, 0);
}
break;
case I2SIOC_GRXCHANNELS:
{
*(FAR int *)arg = I2S_RXCHANNELS(priv->i2s, 0);
}
break;
case I2SIOC_GTXCHANNELS:
{
*(FAR int *)arg = I2S_TXCHANNELS(priv->i2s, 0);
}
break;
case I2SIOC_GRXSAMPLERATE:
{
*(FAR uint32_t *)arg = I2S_RXSAMPLERATE(priv->i2s, 0);
}
break;
case I2SIOC_GTXSAMPLERATE:
{
*(FAR uint32_t *)arg = I2S_TXSAMPLERATE(priv->i2s, 0);
}
break;
case I2SIOC_SRXDATAWIDTH:
{
*(FAR uint32_t *)arg = I2S_RXDATAWIDTH(priv->i2s, arg);
break;
}
case I2SIOC_STXDATAWIDTH:
{
*(FAR uint32_t *)arg = I2S_TXDATAWIDTH(priv->i2s, arg);
}
break;
case I2SIOC_SRXCHANNELS:
{
*(FAR int *)arg = I2S_RXCHANNELS(priv->i2s, arg);
}
break;
case I2SIOC_STXCHANNELS:
{
*(FAR int *)arg = I2S_TXCHANNELS(priv->i2s, arg);
}
break;
case I2SIOC_SRXSAMPLERATE:
{
*(FAR uint32_t *)arg = I2S_RXSAMPLERATE(priv->i2s, arg);
}
break;
case I2SIOC_STXSAMPLERATE:
{
*(FAR uint32_t *)arg = I2S_TXSAMPLERATE(priv->i2s, arg);
}
break;
default:
{
if (priv->i2s->ops->i2s_ioctl)
{
ret = priv->i2s->ops->i2s_ioctl(priv->i2s, cmd, arg);
}
else
{
ret = -ENOTTY;
}
}
break;
}
return ret;
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: i2schar_register
*
* Description:
* Create and register the I2S character driver.
*
* The I2S character driver is a simple character driver that supports I2S
* transfers via a read() and write(). The intent of this driver is to
* support I2S testing. It is not an audio driver but does conform to some
* of the buffer management heuristics of an audio driver. It is not
* suitable for use in any real driver application in its current form.
*
* Input Parameters:
* i2s - An instance of the lower half I2S driver
* minor - The device minor number. The I2S character device will be
* registers as /dev/i2scharN where N is the minor number
*
* Returned Value:
* OK if the driver was successfully register; A negated errno value is
* returned on any failure.
*
****************************************************************************/
int i2schar_register(FAR struct i2s_dev_s *i2s, int minor)
{
FAR struct i2schar_dev_s *priv;
char devname[DEVNAME_FMTLEN];
int ret;
/* Sanity check */
DEBUGASSERT(i2s != NULL && (unsigned)minor < 1000);
/* Allocate a I2S character device structure */
size_t dev_size = sizeof(struct i2schar_dev_s);
priv = kmm_zalloc(dev_size);
if (priv)
{
/* Initialize the I2S character device structure */
priv->i2s = i2s;
nxmutex_init(&priv->rx_lock);
nxmutex_init(&priv->tx_lock);
nxsem_init(&priv->rx_sem, 0, 0);
nxsem_init(&priv->tx_sem, 0, 0);
priv->rx_result = 0;
priv->tx_result = 0;
/* Create the character device name */
snprintf(devname, sizeof(devname), DEVNAME_FMT, minor);
ret = register_driver(devname, &g_i2schar_fops, 0666, priv);
if (ret < 0)
{
/* Free the device structure if we failed to create the character
* device.
*/
nxsem_destroy(&priv->tx_sem);
nxsem_destroy(&priv->rx_sem);
nxmutex_destroy(&priv->rx_lock);
nxmutex_destroy(&priv->tx_lock);
kmm_free(priv);
return ret;
}
/* Return the result of the registration */
return OK;
}
return -ENOMEM;
}
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