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i2cbus.c
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i2cbus.c
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#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <linux/i2c-dev.h>
#include <errno.h>
#include <stdint.h>
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
#include <sys/ioctl.h>
#include <pthread.h>
#define __I2CBUS_INTERNAL
#include "i2cbus.h"
#undef __I2CBUS_INTERNAL
#define eprintf(...) fprintf(stderr, __VA_ARGS__)
static int __i2clock_initd = 0; /// Indicate that the I2C bus has not been initialized
int i2cbus_open(i2cbus *dev, int id, int addr)
{
if (__i2clock_initd++ == 0) // only do it when the lock init is zero
{
for (int i = 0; i < __I2CBUS_MAX_NUM; i++)
{
int ret = pthread_mutex_init(&(__i2cbus_locks[i]), NULL);
if (ret != 0)
{
eprintf("%s: Failed to init mutex %d, ", __func__, i);
perror("mutex init");
return -1;
}
}
}
// check 1: memory
if (dev == NULL)
{
fprintf(stderr, "%s: Error: Device descriptor is NULL\n", __func__);
return -1;
}
// check 2: id > __I2CBUS_MAX_NUM - 1
if (!(id < __I2CBUS_MAX_NUM))
{
fprintf(stderr, "%s: System supports up to %d ID, you provided %d.\n", __func__, __I2CBUS_MAX_NUM - 1, id);
return -1;
}
// check 3: addr valid range
if (addr < 8)
{
fprintf(stderr, "%s: Address 0x%02x is invalid\n", __func__, addr);
return -1;
}
// Try to open the file descriptor
// step 1: Create file name
char fname[256];
if (snprintf(fname, 256, "/dev/i2c-%d", id) < 0)
{
fprintf(stderr, "%s: Failed to generate device filename using snprintf. FATAL Error!\n", __func__);
return -1;
}
if ((dev->fd = open(fname, O_RDWR)) < 0)
{
fprintf(stderr, "%s: Failed to open %s. Error %d\n", __func__, fname, dev->fd);
return dev->fd;
}
int status = 0;
if ((status = ioctl(dev->fd, I2C_SLAVE, addr)) < 0)
{
fprintf(stderr, "%s: Failed to open I2C slave address 0x%02x on bus %s with error %d, returning...\n", __func__, addr, fname, status);
close(dev->fd);
return status;
}
// if we are here, then everything was successful
dev->id = id; // assign device id
dev->lock = &(__i2cbus_locks[id]); // assign lock
dev->ctx = -1; // context has been cleared, it has to be set by the caller
return dev->fd;
}
int i2cbus_close(i2cbus *dev)
{
if (--__i2clock_initd == 0) // only do it when the lock init is zero
{
for (int i = 0; i < __I2CBUS_MAX_NUM; i++)
{
int ret = pthread_mutex_destroy(&(__i2cbus_locks[i]));
if (ret != 0)
{
eprintf("%s: Failed to destroy mutex %d, ", __func__, i);
perror("mutex destroy");
return -1;
}
}
}
if (dev != NULL)
{
if (dev->fd > 0)
return close(dev->fd);
else
{
fprintf(stderr, "%s: %s %d\n", __func__, "Invalid file descriptor", dev->fd);
return -2;
}
}
else
{
fprintf(stderr, "%s: %s\n", __func__, "Invalid device descriptor");
return -3;
}
// will never reach this point
return -1;
}
#define likely(x) __builtin_expect(!!(x), 1)
#define unlikely(x) __builtin_expect(!!(x), 0)
int i2cbus_write(i2cbus *dev, const void *buf, ssize_t len)
{
// usual checks
if (unlikely(dev == NULL || dev->fd < 0))
{
fprintf(stderr, "%s: %s %p, %d\n", __func__, "Invalid device pointer or file descriptor", dev, dev->fd);
return -1;
}
// check if it belongs to a context
int locked = 1;
int status = 0;
if (!(dev->ctx < I2CBUS_CTX_0 || dev->ctx > I2CBUS_CTX_9))
{
status = pthread_mutex_trylock(dev->lock);
// valid context found, check if there is a lock
if (status == EBUSY || status == EINVAL)
locked = 0;
}
// otherwise try to lock and block on it
else
status = pthread_mutex_lock(dev->lock);
if (status == EDEADLK) // we already own the mutex
locked = 0;
status = write(dev->fd, buf, len);
if (status != len)
{
#ifdef I2C_DEBUG
fprintf(stderr, "%s: Failed to write %ld bytes, wrote %d bytes\n", __func__, len, status);
#endif
}
if (locked)
pthread_mutex_unlock(dev->lock);
return status;
}
int i2cbus_read(i2cbus *dev, void *buf, ssize_t len)
{
// usual checks
if (unlikely(dev == NULL || dev->fd < 0))
{
fprintf(stderr, "%s: %s %p, %d\n", __func__, "Invalid device pointer or file descriptor", dev, dev->fd);
return -1;
}
// check if it belongs to a context
int locked = 1;
int status = 0;
if (!(dev->ctx < I2CBUS_CTX_0 || dev->ctx > I2CBUS_CTX_9))
{
status = pthread_mutex_trylock(dev->lock);
// valid context found, check if there is a lock
if (status == EBUSY || status == EINVAL)
locked = 0;
}
// otherwise try to lock and block on it
else
status = pthread_mutex_lock(dev->lock);
if (status == EDEADLK) // we already own the mutex
locked = 0;
status = read(dev->fd, buf, len);
if (status != len)
{
#ifdef I2C_DEBUG
fprintf(stderr, "%s: Failed to read %ld bytes, read %d bytes\n", __func__, len, status);
#endif
}
if (locked)
pthread_mutex_unlock(dev->lock);
return status;
}
int i2cbus_xfer(i2cbus *dev,
void *outbuf, ssize_t outlen,
void *inbuf, ssize_t inlen,
unsigned long timeout_usec)
{
// usual checks
if (unlikely(dev == NULL || dev->fd < 0))
{
fprintf(stderr, "%s: %s %p, %d\n", __func__, "Invalid device pointer or file descriptor", dev, dev->fd);
return -1;
}
// check if it belongs to a context
int locked = 1;
int status = 0;
if (!(dev->ctx < I2CBUS_CTX_0 || dev->ctx > I2CBUS_CTX_9))
{
status = pthread_mutex_trylock(dev->lock);
// valid context found, check if there is a lock
if (status == EBUSY || status == EINVAL)
locked = 0;
#ifdef I2C_DEBUG
eprintf("%s: Contex found, cts: 0x%02x, status: %d, locked: %d\n", __func__, dev->ctx, status, locked);
#endif
}
// otherwise try to lock and block on it
else
status = pthread_mutex_lock(dev->lock);
if (status == EDEADLK) // we already own the mutex
locked = 0;
#ifdef I2C_DEBUG
eprintf("%s: Sending %d bytes ->\n", __func__, outlen);
for (int i = 0; i < outlen; i++)
{
eprintf("[0x%02x]", ((unsigned char *)outbuf)[i]);
}
eprintf("\n");
#endif
status = write(dev->fd, outbuf, outlen);
if (status != outlen)
{
fprintf(stderr, "%s: Failed to write %d bytes, wrote %d bytes\n", __func__, outlen, status);
goto i2cbus_xfer_end;
}
if (timeout_usec > 0)
usleep(timeout_usec);
status = read(dev->fd, inbuf, inlen);
if (status != inlen)
{
#ifdef I2C_DEBUG
fprintf(stderr, "%s: Failed to read %d bytes, read %d bytes\n", __func__, inlen, status);
#endif
}
#ifdef I2C_DEBUG
eprintf("%s: Receiving %d bytes ->\n", __func__, inlen);
for (int i = 0; i < inlen; i++)
{
eprintf("[0x%02x]", ((unsigned char *)inbuf)[i]);
}
eprintf("\n");
#endif
i2cbus_xfer_end:
if (locked)
pthread_mutex_unlock(dev->lock);
return status;
}
int i2cbus_lock(i2cbus *dev)
{
if (likely(!(dev->ctx < I2CBUS_CTX_0 || dev->ctx > I2CBUS_CTX_9)))
{
return pthread_mutex_lock(dev->lock);
}
else
return -EINVAL;
}
int i2cbus_trylock(i2cbus *dev)
{
if (likely(!(dev->ctx < I2CBUS_CTX_0 || dev->ctx > I2CBUS_CTX_9)))
{
return pthread_mutex_trylock(dev->lock);
}
else
return -EINVAL;
}
int i2cbus_unlock(i2cbus *dev)
{
if (likely(!(dev->ctx < I2CBUS_CTX_0 || dev->ctx > I2CBUS_CTX_9)))
{
return pthread_mutex_unlock(dev->lock);
}
else
return -EINVAL;
}