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smbus.c
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smbus.c
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/* SPDX-License-Identifier: Apache-2.0 */
#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <linux/errno-base.h>
#ifdef MCTP_HAVE_FILEIO
#include <fcntl.h>
#endif
#define pr_fmt(x) "smbus: " x
#include <i2c/smbus.h>
#include <linux/i2c-dev.h>
#include <linux/i2c.h>
#include <sys/ioctl.h>
#include "libmctp-alloc.h"
#include "libmctp-log.h"
#include "libmctp-smbus.h"
#include "libmctp.h"
#ifndef container_of
#define container_of(ptr, type, member) \
(type *)((char *)(ptr) - (char *)&((type *)0)->member)
#endif
#define binding_to_smbus(b) container_of(b, struct mctp_binding_smbus, binding)
#define MCTP_COMMAND_CODE 0x0F
#define MCTP_SLAVE_ADDR_INDEX 0
#define DEFAULT_SLAVE_ADDRESS 0x21
#define SMBUS_COMMAND_CODE_SIZE 1
#define SMBUS_LENGTH_FIELD_SIZE 1
#define SMBUS_ADDR_OFFSET_SLAVE 0x1000
#ifdef I2C_M_HOLD
static struct mctp_smbus_pkt_private active_mux_info = { .fd = -1,
.mux_hold_timeout = 0,
.mux_flags = 0,
.slave_addr = 0 };
static struct mctp_smbus_pkt_private reserve_mux_info = { .fd = -1,
.mux_hold_timeout = 0,
.mux_flags = 0,
.slave_addr = 0 };
#endif
struct mctp_smbus_header_tx {
uint8_t command_code;
uint8_t byte_count;
uint8_t source_slave_address;
};
struct mctp_smbus_header_rx {
uint8_t destination_slave_address;
uint8_t command_code;
uint8_t byte_count;
uint8_t source_slave_address;
};
static uint8_t crc8_calculate(uint16_t d)
{
const uint32_t poly_check = 0x1070 << 3;
int i;
for (i = 0; i < 8; i++) {
if (d & 0x8000) {
d = d ^ poly_check;
}
d = d << 1;
}
return (uint8_t)(d >> 8);
}
/* Incremental CRC8 over count bytes in the array pointed to by p */
static uint8_t pec_calculate(uint8_t crc, uint8_t *p, size_t count)
{
int i;
for (i = 0; i < count; i++) {
crc = crc8_calculate((crc ^ p[i]) << 8);
}
return crc;
}
static uint8_t calculate_pec_byte(uint8_t *buf, size_t len, uint8_t address)
{
uint8_t pec = pec_calculate(0, &address, 1);
pec = pec_calculate(pec, buf, len);
return pec;
}
#ifdef I2C_M_HOLD
static void cleanup_reserve_mux_info(void)
{
reserve_mux_info.fd = -1;
reserve_mux_info.mux_hold_timeout = 0;
reserve_mux_info.mux_flags = 0;
reserve_mux_info.slave_addr = 0;
}
static int smbus_model_mux(const uint16_t holdtimeout)
{
struct i2c_msg holdmsg = { 0, I2C_M_HOLD, sizeof(holdtimeout),
(uint8_t *)&holdtimeout };
struct i2c_rdwr_ioctl_data msgrdwr = { &holdmsg, 1 };
return ioctl(reserve_mux_info.fd, I2C_RDWR, &msgrdwr);
}
static int smbus_pull_model_hold_mux(void)
{
/*taking max hold time as 0xFFFF seconds*/
return smbus_model_mux(0xFFFF);
}
static int smbus_pull_model_unhold_mux(void)
{
return smbus_model_mux(0);
}
static bool pull_model_active;
#endif
int mctp_smbus_close_mux(const int fd, const int address)
{
#ifdef I2C_M_HOLD
uint8_t txbuf[2] = { 0 };
struct i2c_msg msg[1] = {
{ .addr = address, .flags = 0, .len = 2, .buf = txbuf }
};
struct i2c_rdwr_ioctl_data msgrdwr = { &msg[0], 1 };
return ioctl(fd, I2C_RDWR, &msgrdwr);
#else
return 0;
#endif
}
int mctp_smbus_init_pull_model(const struct mctp_smbus_pkt_private *prvt)
{
#ifdef I2C_M_HOLD
int rc = -1;
if (pull_model_active) {
mctp_prerr("%s: pull model is already active.", __func__);
return rc;
}
reserve_mux_info.fd = prvt->fd;
reserve_mux_info.mux_flags = prvt->mux_flags;
reserve_mux_info.slave_addr = prvt->slave_addr;
rc = smbus_pull_model_hold_mux();
if (rc < 0) {
cleanup_reserve_mux_info();
mctp_prerr(
"%s: Failed to hold the bus for device address: 0X%x",
__func__, prvt->slave_addr);
return rc;
}
pull_model_active = true;
return rc;
#else
return 0;
#endif
}
int mctp_smbus_exit_pull_model(const struct mctp_smbus_pkt_private *prvt)
{
#ifdef I2C_M_HOLD
int rc = -1;
if (!(pull_model_active &&
reserve_mux_info.slave_addr == prvt->slave_addr &&
reserve_mux_info.fd == prvt->fd)) {
mctp_prerr(
"%s: pull model is not active for device address: 0X%x.",
__func__, prvt->slave_addr);
return rc;
}
rc = smbus_pull_model_unhold_mux();
if (rc < 0) {
mctp_prerr(
"%s: Failed to unhold the bus for device address: 0X%x",
__func__, prvt->slave_addr);
return rc;
}
pull_model_active = false;
cleanup_reserve_mux_info();
return rc;
#else
return 0;
#endif
}
static int mctp_smbus_tx(struct mctp_binding_smbus *smbus, const uint8_t len,
struct mctp_smbus_pkt_private *pkt_pvt)
{
#ifdef I2C_M_HOLD
int rc;
if (pull_model_active) {
rc = smbus_pull_model_unhold_mux();
if (rc < 0) {
mctp_prerr("%s: Failed to unhold the bus.", __func__);
return rc;
}
}
if (pkt_pvt->mux_flags) {
uint16_t holdtimeout =
pkt_pvt->mux_hold_timeout; /*timeout in ms. */
struct i2c_msg msg[2] = { { .addr = pkt_pvt->slave_addr >>
1, /* seven bit address */
.flags = 0,
.len = len,
.buf = smbus->txbuf },
{ .addr = 0,
.flags = I2C_M_HOLD,
.len = sizeof(holdtimeout),
.buf = (uint8_t *)&holdtimeout } };
struct i2c_rdwr_ioctl_data msgrdwr = { &msg[0], 2 };
mctp_trace_tx(smbus->txbuf, len);
rc = ioctl(pkt_pvt->fd, I2C_RDWR, &msgrdwr);
/* Store active mux info */
active_mux_info.fd = pkt_pvt->fd;
active_mux_info.mux_flags = pkt_pvt->mux_flags;
active_mux_info.slave_addr = pkt_pvt->slave_addr;
return rc;
}
#endif
mctp_trace_tx(smbus->txbuf, len);
struct i2c_msg msg[1] = { { .addr = pkt_pvt->slave_addr >>
1, /* seven bit address */
.flags = 0,
.len = len,
.buf = smbus->txbuf } };
struct i2c_rdwr_ioctl_data msgrdwr = { &msg[0], 1 };
return ioctl(pkt_pvt->fd, I2C_RDWR, &msgrdwr);
}
#ifdef I2C_M_HOLD
static int mctp_smbus_unhold_bus(const uint8_t source_addr)
{
/* If we received a packet from a different slave, don't unhold mux */
if (active_mux_info.slave_addr != source_addr)
return 0;
/* Unhold message */
uint16_t holdtimeout = 0;
struct i2c_msg holdmsg = { 0, I2C_M_HOLD, sizeof(holdtimeout),
(uint8_t *)&holdtimeout };
struct i2c_rdwr_ioctl_data msgrdwr = { &holdmsg, 1 };
return ioctl(active_mux_info.fd, I2C_RDWR, &msgrdwr);
}
#endif /* I2C_M_HOLD */
static int mctp_binding_smbus_tx(struct mctp_binding *b,
struct mctp_pktbuf *pkt)
{
struct mctp_binding_smbus *smbus = binding_to_smbus(b);
struct mctp_smbus_header_tx *smbus_hdr_tx = (void *)smbus->txbuf;
struct mctp_smbus_pkt_private *pkt_pvt =
(struct mctp_smbus_pkt_private *)pkt->msg_binding_private;
#ifdef I2C_M_HOLD
struct mctp_hdr *mctp_hdr = (void *)(&pkt->data[pkt->start]);
/* Set mux_flags only for EOM packets */
if (!(mctp_hdr->flags_seq_tag & MCTP_HDR_FLAG_EOM)) {
pkt_pvt->mux_flags = 0;
}
#endif
smbus_hdr_tx->command_code = MCTP_COMMAND_CODE;
if (!pkt_pvt) {
mctp_prerr("Binding private information not available");
return -EINVAL;
}
/* the length field in the header excludes smbus framing
* and escape sequences.
*/
size_t pkt_length = mctp_pktbuf_size(pkt);
smbus_hdr_tx->byte_count = pkt_length + 1;
smbus_hdr_tx->source_slave_address = smbus->src_slave_addr;
size_t tx_buf_len = sizeof(*smbus_hdr_tx);
uint8_t i2c_message_len = tx_buf_len + pkt_length + SMBUS_PEC_BYTE_SIZE;
if (i2c_message_len > sizeof(smbus->txbuf)) {
mctp_prerr(
"tx message length exceeds max smbus message length");
return -EINVAL;
}
memcpy(smbus->txbuf + tx_buf_len, &pkt->data[pkt->start], pkt_length);
tx_buf_len += pkt_length;
smbus->txbuf[tx_buf_len] = calculate_pec_byte(smbus->txbuf, tx_buf_len,
pkt_pvt->slave_addr);
int ret = mctp_smbus_tx(smbus, i2c_message_len, pkt_pvt);
if (ret == -EPERM) {
mctp_prdebug(
"Error in tx of smbus message; Operation not permitted");
return ret;
}
if (ret < 0) {
mctp_prerr("Error in tx of smbus message");
return ret;
}
return 0;
}
#ifdef MCTP_HAVE_FILEIO
int mctp_smbus_read(struct mctp_binding_smbus *smbus)
{
ssize_t len = 0;
struct mctp_smbus_header_rx *smbus_hdr_rx;
struct mctp_smbus_pkt_private pvt_data;
uint8_t rx_pec;
#ifdef I2C_M_HOLD
struct mctp_hdr *mctp_hdr;
bool eom = false;
#endif
smbus_hdr_rx = (void *)smbus->rxbuf;
int ret = lseek(smbus->in_fd, 0, SEEK_SET);
if (ret < 0) {
mctp_prerr("Failed to seek");
return -1;
}
len = read(smbus->in_fd, smbus->rxbuf, sizeof(smbus->rxbuf));
if (len < 0) {
mctp_prerr("Failed to read");
return -1;
}
mctp_trace_rx(smbus->rxbuf, len);
if (len < sizeof(*smbus_hdr_rx)) {
/* This condition hits from time to time, even with
* a properly written poll loop, although it's not clear
* why. Return an error so that the upper layer can
* retry.
*/
mctp_prerr("Invalid packet size");
return 0;
}
else if (smbus_hdr_rx->byte_count != (len - sizeof(*smbus_hdr_rx))) {
/* Got an incorrectly sized payload */
mctp_prerr("Got smbus payload sized %zu, expecting %hhu",
len - sizeof(*smbus_hdr_rx),
smbus_hdr_rx->byte_count);
return 0;
}
if (smbus_hdr_rx->destination_slave_address !=
(smbus->src_slave_addr & ~1)) {
mctp_prerr("Got bad slave address %d",
smbus_hdr_rx->destination_slave_address);
return 0;
}
if (smbus_hdr_rx->command_code != MCTP_COMMAND_CODE) {
mctp_prerr("Got bad command code %d",
smbus_hdr_rx->command_code);
/* Not a payload intended for us */
return 0;
}
rx_pec = pec_calculate(0, smbus->rxbuf, len - 1);
if (rx_pec != smbus->rxbuf[len - 1]) {
mctp_prerr("Invalid PEC value: expected: 0x%02x, found 0x%02x",
rx_pec, smbus->rxbuf[len - 1]);
return -1;
}
smbus->rx_pkt = mctp_pktbuf_alloc(&(smbus->binding), 0);
if (!smbus->rx_pkt) {
mctp_prerr("Cannot allocate memory");
return -1;
}
if (mctp_pktbuf_push(
smbus->rx_pkt, &smbus->rxbuf[sizeof(*smbus_hdr_rx)],
len - sizeof(*smbus_hdr_rx) - SMBUS_PEC_BYTE_SIZE) != 0) {
mctp_prerr("Can't push to pktbuf: %m");
mctp_pktbuf_free(smbus->rx_pkt);
return -1;
}
#ifdef I2C_M_HOLD
mctp_hdr = mctp_pktbuf_hdr(smbus->rx_pkt);
if (mctp_hdr->flags_seq_tag & MCTP_HDR_FLAG_EOM) {
eom = true;
}
#endif
memset(&pvt_data, 0, sizeof(struct mctp_smbus_pkt_private));
pvt_data.slave_addr = (smbus_hdr_rx->source_slave_address & ~1);
pvt_data.fd = smbus->out_fd;
memcpy(smbus->rx_pkt->msg_binding_private, &pvt_data, sizeof(pvt_data));
mctp_bus_rx(&(smbus->binding), smbus->rx_pkt);
#ifdef I2C_M_HOLD
/* Unhold mux only for packets with EOM */
if (eom && mctp_smbus_unhold_bus(pvt_data.slave_addr)) {
mctp_prerr("Can't hold mux");
return -1;
}
#endif // I2C_M_HOLD
smbus->rx_pkt = NULL;
return 0;
}
void mctp_smbus_set_in_fd(struct mctp_binding_smbus *smbus, int fd)
{
smbus->in_fd = fd;
}
void mctp_smbus_set_out_fd(struct mctp_binding_smbus *smbus, int fd)
{
smbus->out_fd = fd;
}
#endif
int mctp_smbus_register_bus(struct mctp_binding_smbus *smbus, struct mctp *mctp,
mctp_eid_t eid)
{
int rc = mctp_register_bus(mctp, &smbus->binding, eid);
if (rc == 0) {
/* TODO: Can we drop bus_id from mctp_binding_smbus? */
smbus->bus_id = 0;
mctp_binding_set_tx_enabled(&smbus->binding, true);
}
return rc;
}
struct mctp_binding_smbus *mctp_smbus_init(void)
{
struct mctp_binding_smbus *smbus;
smbus = __mctp_alloc(sizeof(*smbus));
memset(&(smbus->binding), 0, sizeof(smbus->binding));
smbus->in_fd = -1;
smbus->out_fd = -1;
smbus->rx_pkt = NULL;
smbus->binding.name = "smbus";
smbus->binding.version = 1;
smbus->binding.pkt_size = MCTP_PACKET_SIZE(MCTP_BTU);
smbus->binding.pkt_pad = SMBUS_HEADER_SIZE;
smbus->binding.pkt_priv_size = sizeof(struct mctp_smbus_pkt_private);
smbus->binding.tx = mctp_binding_smbus_tx;
/* Setting the default slave address */
smbus->src_slave_addr = DEFAULT_SLAVE_ADDRESS;
return smbus;
}
void mctp_smbus_free(struct mctp_binding_smbus *smbus)
{
if (!(smbus->in_fd < 0)) {
close(smbus->in_fd);
}
if (!(smbus->out_fd < 0)) {
close(smbus->out_fd);
}
__mctp_free(smbus);
}
void mctp_smbus_set_src_slave_addr(struct mctp_binding_smbus *smbus,
uint8_t slave_addr)
{
smbus->src_slave_addr = slave_addr;
}