103 lines
2.5 KiB
C
103 lines
2.5 KiB
C
// Linux i2c implementation
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//
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// Copyright (C) 2020 Eric Callahan <arksine.code@gmail.com>
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//
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// This file may be distributed under the terms of the GNU GPLv3 license.
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#include <fcntl.h> // open
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#include <linux/i2c-dev.h> // I2C_SLAVE
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#include <stdio.h> // snprintf
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#include <sys/ioctl.h> // ioctl
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#include <unistd.h> // write
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#include "gpio.h" // i2c_setup
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#include "command.h" // shutdown
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#include "internal.h" // report_errno
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#include "sched.h" // sched_shutdown
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DECL_ENUMERATION_RANGE("i2c_bus", "i2c.0", 0, 2);
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struct i2c_s {
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uint32_t bus;
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uint8_t addr;
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int fd;
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};
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static struct i2c_s devices[16];
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static int devices_count;
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static int
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i2c_open(uint32_t bus, uint8_t addr)
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{
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// Find existing device (if already opened)
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int i;
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for (i=0; i<devices_count; i++) {
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if (devices[i].bus == bus && devices[i].addr == addr) {
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return devices[i].fd;
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}
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}
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char fname[256];
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snprintf(fname, sizeof(fname), "/dev/i2c-%d", bus);
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int fd = open(fname, O_RDWR|O_CLOEXEC);
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if (fd < 0) {
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report_errno("open i2c", fd);
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goto fail;
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}
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int ret = ioctl(fd, I2C_SLAVE, addr);
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if (ret < 0) {
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report_errno("ioctl i2c", fd);
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goto fail;
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}
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ret = set_non_blocking(fd);
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if (ret < 0)
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goto fail;
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devices[devices_count].bus = bus;
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devices[devices_count].addr = addr;
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devices[devices_count].fd = fd;
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devices_count++;
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return fd;
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fail:
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if (fd >= 0)
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close(fd);
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shutdown("Unable to open i2c device");
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}
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struct i2c_config
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i2c_setup(uint32_t bus, uint32_t rate, uint8_t addr)
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{
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// Note: The rate is set by the kernel driver, for a Raspberry Pi this
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// is done with the following setting in /boot/config.txt:
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//
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// dtparam=i2c_baudrate=<rate>
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int fd = i2c_open(bus, addr);
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return (struct i2c_config){.fd=fd};
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}
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void
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i2c_write(struct i2c_config config, uint8_t write_len, uint8_t *data)
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{
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int ret = write(config.fd, data, write_len);
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if (ret != write_len) {
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if (ret < 0)
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report_errno("write value i2c", ret);
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try_shutdown("Unable write i2c device");
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}
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}
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void
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i2c_read(struct i2c_config config, uint8_t reg_len, uint8_t *reg
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, uint8_t read_len, uint8_t *data)
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{
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if(reg_len != 0)
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i2c_write(config, reg_len, reg);
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int ret = read(config.fd, data, read_len);
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if (ret != read_len) {
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if (ret < 0)
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report_errno("read value i2c", ret);
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try_shutdown("Unable to read i2c device");
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}
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}
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