ipmb_dev_int.c
// SPDX-License-Identifier: GPL-2.0
/*
* IPMB driver to receive a request and send a response
*
* Copyright (C) 2019 Mellanox Techologies, Ltd.
*
* This was inspired by Brendan Higgins' ipmi-bmc-bt-i2c driver.
*/
#include <linux/acpi.h>
#include <linux/errno.h>
#include <linux/i2c.h>
#include <linux/miscdevice.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/poll.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/wait.h>
#define MAX_MSG_LEN 240
#define IPMB_REQUEST_LEN_MIN 7
#define NETFN_RSP_BIT_MASK 0x4
#define REQUEST_QUEUE_MAX_LEN 256
#define IPMB_MSG_LEN_IDX 0
#define RQ_SA_8BIT_IDX 1
#define NETFN_LUN_IDX 2
#define GET_7BIT_ADDR(addr_8bit) (addr_8bit >> 1)
#define GET_8BIT_ADDR(addr_7bit) ((addr_7bit << 1) & 0xff)
#define IPMB_MSG_PAYLOAD_LEN_MAX (MAX_MSG_LEN - IPMB_REQUEST_LEN_MIN - 1)
#define SMBUS_MSG_HEADER_LENGTH 2
#define SMBUS_MSG_IDX_OFFSET (SMBUS_MSG_HEADER_LENGTH + 1)
struct ipmb_msg {
u8 len;
u8 rs_sa;
u8 netfn_rs_lun;
u8 checksum1;
u8 rq_sa;
u8 rq_seq_rq_lun;
u8 cmd;
u8 payload[IPMB_MSG_PAYLOAD_LEN_MAX];
/* checksum2 is included in payload */
} __packed;
struct ipmb_request_elem {
struct list_head list;
struct ipmb_msg request;
};
struct ipmb_dev {
struct i2c_client *client;
struct miscdevice miscdev;
struct ipmb_msg request;
struct list_head request_queue;
atomic_t request_queue_len;
size_t msg_idx;
spinlock_t lock;
wait_queue_head_t wait_queue;
struct mutex file_mutex;
bool is_i2c_protocol;
};
static inline struct ipmb_dev *to_ipmb_dev(struct file *file)
{
return container_of(file->private_data, struct ipmb_dev, miscdev);
}
static ssize_t ipmb_read(struct file *file, char __user *buf, size_t count,
loff_t *ppos)
{
struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
struct ipmb_request_elem *queue_elem;
struct ipmb_msg msg;
ssize_t ret = 0;
memset(&msg, 0, sizeof(msg));
spin_lock_irq(&ipmb_dev->lock);
while (list_empty(&ipmb_dev->request_queue)) {
spin_unlock_irq(&ipmb_dev->lock);
if (file->f_flags & O_NONBLOCK)
return -EAGAIN;
ret = wait_event_interruptible(ipmb_dev->wait_queue,
!list_empty(&ipmb_dev->request_queue));
if (ret)
return ret;
spin_lock_irq(&ipmb_dev->lock);
}
queue_elem = list_first_entry(&ipmb_dev->request_queue,
struct ipmb_request_elem, list);
memcpy(&msg, &queue_elem->request, sizeof(msg));
list_del(&queue_elem->list);
kfree(queue_elem);
atomic_dec(&ipmb_dev->request_queue_len);
spin_unlock_irq(&ipmb_dev->lock);
count = min_t(size_t, count, msg.len + 1);
if (copy_to_user(buf, &msg, count))
ret = -EFAULT;
return ret < 0 ? ret : count;
}
static int ipmb_i2c_write(struct i2c_client *client, u8 *msg, u8 addr)
{
struct i2c_msg i2c_msg;
/*
* subtract 1 byte (rq_sa) from the length of the msg passed to
* raw i2c_transfer
*/
i2c_msg.len = msg[IPMB_MSG_LEN_IDX] - 1;
/* Assign message to buffer except first 2 bytes (length and address) */
i2c_msg.buf = msg + 2;
i2c_msg.addr = addr;
i2c_msg.flags = client->flags & I2C_CLIENT_PEC;
return i2c_transfer(client->adapter, &i2c_msg, 1);
}
static ssize_t ipmb_write(struct file *file, const char __user *buf,
size_t count, loff_t *ppos)
{
struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
u8 rq_sa, netf_rq_lun, msg_len;
struct i2c_client *temp_client;
u8 msg[MAX_MSG_LEN];
ssize_t ret;
if (count > sizeof(msg))
return -EINVAL;
if (copy_from_user(&msg, buf, count))
return -EFAULT;
if (count < msg[0])
return -EINVAL;
rq_sa = GET_7BIT_ADDR(msg[RQ_SA_8BIT_IDX]);
netf_rq_lun = msg[NETFN_LUN_IDX];
/* Check i2c block transfer vs smbus */
if (ipmb_dev->is_i2c_protocol) {
ret = ipmb_i2c_write(ipmb_dev->client, msg, rq_sa);
return (ret == 1) ? count : ret;
}
/*
* subtract rq_sa and netf_rq_lun from the length of the msg. Fill the
* temporary client. Note that its use is an exception for IPMI.
*/
msg_len = msg[IPMB_MSG_LEN_IDX] - SMBUS_MSG_HEADER_LENGTH;
temp_client = kmemdup(ipmb_dev->client, sizeof(*temp_client), GFP_KERNEL);
if (!temp_client)
return -ENOMEM;
temp_client->addr = rq_sa;
ret = i2c_smbus_write_block_data(temp_client, netf_rq_lun, msg_len,
msg + SMBUS_MSG_IDX_OFFSET);
kfree(temp_client);
return ret < 0 ? ret : count;
}
static __poll_t ipmb_poll(struct file *file, poll_table *wait)
{
struct ipmb_dev *ipmb_dev = to_ipmb_dev(file);
__poll_t mask = EPOLLOUT;
mutex_lock(&ipmb_dev->file_mutex);
poll_wait(file, &ipmb_dev->wait_queue, wait);
if (atomic_read(&ipmb_dev->request_queue_len))
mask |= EPOLLIN;
mutex_unlock(&ipmb_dev->file_mutex);
return mask;
}
static const struct file_operations ipmb_fops = {
.owner = THIS_MODULE,
.read = ipmb_read,
.write = ipmb_write,
.poll = ipmb_poll,
};
/* Called with ipmb_dev->lock held. */
static void ipmb_handle_request(struct ipmb_dev *ipmb_dev)
{
struct ipmb_request_elem *queue_elem;
if (atomic_read(&ipmb_dev->request_queue_len) >=
REQUEST_QUEUE_MAX_LEN)
return;
queue_elem = kmalloc(sizeof(*queue_elem), GFP_ATOMIC);
if (!queue_elem)
return;
memcpy(&queue_elem->request, &ipmb_dev->request,
sizeof(struct ipmb_msg));
list_add(&queue_elem->list, &ipmb_dev->request_queue);
atomic_inc(&ipmb_dev->request_queue_len);
wake_up_all(&ipmb_dev->wait_queue);
}
static u8 ipmb_verify_checksum1(struct ipmb_dev *ipmb_dev, u8 rs_sa)
{
/* The 8 lsb of the sum is 0 when the checksum is valid */
return (rs_sa + ipmb_dev->request.netfn_rs_lun +
ipmb_dev->request.checksum1);
}
/*
* Verify if message has proper ipmb header with minimum length
* and correct checksum byte.
*/
static bool is_ipmb_msg(struct ipmb_dev *ipmb_dev, u8 rs_sa)
{
if ((ipmb_dev->msg_idx >= IPMB_REQUEST_LEN_MIN) &&
(!ipmb_verify_checksum1(ipmb_dev, rs_sa)))
return true;
return false;
}
/*
* The IPMB protocol only supports I2C Writes so there is no need
* to support I2C_SLAVE_READ* events.
* This i2c callback function only monitors IPMB request messages
* and adds them in a queue, so that they can be handled by
* receive_ipmb_request.
*/
static int ipmb_slave_cb(struct i2c_client *client,
enum i2c_slave_event event, u8 *val)
{
struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client);
u8 *buf = (u8 *)&ipmb_dev->request;
unsigned long flags;
spin_lock_irqsave(&ipmb_dev->lock, flags);
switch (event) {
case I2C_SLAVE_WRITE_REQUESTED:
memset(&ipmb_dev->request, 0, sizeof(ipmb_dev->request));
ipmb_dev->msg_idx = 0;
/*
* At index 0, ipmb_msg stores the length of msg,
* skip it for now.
* The len will be populated once the whole
* buf is populated.
*
* The I2C bus driver's responsibility is to pass the
* data bytes to the backend driver; it does not
* forward the i2c slave address.
* Since the first byte in the IPMB message is the
* address of the responder, it is the responsibility
* of the IPMB driver to format the message properly.
* So this driver prepends the address of the responder
* to the received i2c data before the request message
* is handled in userland.
*/
buf[++ipmb_dev->msg_idx] = GET_8BIT_ADDR(client->addr);
break;
case I2C_SLAVE_WRITE_RECEIVED:
if (ipmb_dev->msg_idx >= sizeof(struct ipmb_msg) - 1)
break;
buf[++ipmb_dev->msg_idx] = *val;
break;
case I2C_SLAVE_STOP:
ipmb_dev->request.len = ipmb_dev->msg_idx;
if (is_ipmb_msg(ipmb_dev, GET_8BIT_ADDR(client->addr)))
ipmb_handle_request(ipmb_dev);
break;
default:
break;
}
spin_unlock_irqrestore(&ipmb_dev->lock, flags);
return 0;
}
static int ipmb_probe(struct i2c_client *client)
{
struct ipmb_dev *ipmb_dev;
int ret;
ipmb_dev = devm_kzalloc(&client->dev, sizeof(*ipmb_dev),
GFP_KERNEL);
if (!ipmb_dev)
return -ENOMEM;
spin_lock_init(&ipmb_dev->lock);
init_waitqueue_head(&ipmb_dev->wait_queue);
atomic_set(&ipmb_dev->request_queue_len, 0);
INIT_LIST_HEAD(&ipmb_dev->request_queue);
mutex_init(&ipmb_dev->file_mutex);
ipmb_dev->miscdev.minor = MISC_DYNAMIC_MINOR;
ipmb_dev->miscdev.name = devm_kasprintf(&client->dev, GFP_KERNEL,
"%s%d", "ipmb-",
client->adapter->nr);
ipmb_dev->miscdev.fops = &ipmb_fops;
ipmb_dev->miscdev.parent = &client->dev;
ret = misc_register(&ipmb_dev->miscdev);
if (ret)
return ret;
ipmb_dev->is_i2c_protocol
= device_property_read_bool(&client->dev, "i2c-protocol");
ipmb_dev->client = client;
i2c_set_clientdata(client, ipmb_dev);
ret = i2c_slave_register(client, ipmb_slave_cb);
if (ret) {
misc_deregister(&ipmb_dev->miscdev);
return ret;
}
return 0;
}
static void ipmb_remove(struct i2c_client *client)
{
struct ipmb_dev *ipmb_dev = i2c_get_clientdata(client);
i2c_slave_unregister(client);
misc_deregister(&ipmb_dev->miscdev);
}
static const struct i2c_device_id ipmb_id[] = {
{ "ipmb-dev", 0 },
{},
};
MODULE_DEVICE_TABLE(i2c, ipmb_id);
static const struct acpi_device_id acpi_ipmb_id[] = {
{ "IPMB0001", 0 },
{},
};
MODULE_DEVICE_TABLE(acpi, acpi_ipmb_id);
static struct i2c_driver ipmb_driver = {
.driver = {
.name = "ipmb-dev",
.acpi_match_table = ACPI_PTR(acpi_ipmb_id),
},
.probe_new = ipmb_probe,
.remove = ipmb_remove,
.id_table = ipmb_id,
};
module_i2c_driver(ipmb_driver);
MODULE_AUTHOR("Mellanox Technologies");
MODULE_DESCRIPTION("IPMB driver");
MODULE_LICENSE("GPL v2");