[PATCH v10 1/3] ipmi: ssif_bmc: Add SSIF BMC driver
Graeme Gregory
quic_ggregory at quicinc.com
Mon Oct 10 22:08:24 AEDT 2022
On 10/10/2022 02:28, Quan Nguyen wrote:
>
>
> On 07/10/2022 20:26, Graeme Gregory wrote:
>>
>> On 04/10/2022 10:31, Quan Nguyen wrote:
>>> The SMBus system interface (SSIF) IPMI BMC driver can be used to
>>> perform
>>> in-band IPMI communication with their host in management (BMC) side.
>>>
>>> Thanks Dan for the copy_from_user() fix in the link below.
>>>
>>> Link:
>>> https://lore.kernel.org/linux-arm-kernel/20220310114119.13736-4-quan@os.amperecomputing.com/
>>> Signed-off-by: Quan Nguyen <quan at os.amperecomputing.com>
>>
>> I have been testing this on our hardware and I don't seem to be able
>> to get this driver working. I was using an older version.
>>
>> I have hacked ssifbridged to deal with the change in len from u8 to
>> unsigned int.
>>
>> It works as long as I only ever send SSIF commands, any attempt to
>> read a response crashes the state machine and the driver never
>> recovers. No further SSIF comms is possible! (slave doesnt even ACK
>> writes).
>>
>> A couple of comments below on possible state machine errors.
>>
>> Its possible I am doing something wrong!
>>
>
> Thanks Graeme for the test and the comments.
>
> What's your testing hardware?
>
> This was tested with Aspeed ast2500 and ast2600 with the patch series
> [1] below applied.
>
> If you use the same hw, could you pick the series and see if any thing
> improve ?
>
> [1]
> https://lore.kernel.org/all/20210616031046.2317-1-quan@os.amperecomputing.com/
>
Thanks, that patch series does stop the state machine crashing.
I am testing on AST2600EVB with A1 rev, but we also have our own DC-SCM
with A3 chip.
Responses are still not working for me, but I think that may be an error
in my ssifbridged hacks.
Oct 10 10:54:55 qcom-evb-proto-ccf37d18ea0c ssifbridged[335]: Read ssif
request message with len=13 netfn=44 lun=0 cmd=2
Oct 10 10:54:55 qcom-evb-proto-ccf37d18ea0c ipmid[312]: BootCode:
000000000000000000
Oct 10 10:54:55 qcom-evb-proto-ccf37d18ea0c ssifbridged[335]: Send ssif
respond message with len=4 netfn=45 lun=0 cmd=2 cc=0
Oct 10 10:54:55 qcom-evb-proto-ccf37d18ea0c kernel: ipmi-ssif-host
0-0010: Warn: on_read_requested_event unexpected READ REQUESTED in
state=SSIF_READY
Oct 10 10:54:55 qcom-evb-proto-ccf37d18ea0c kernel: ipmi-ssif-host
0-0010: Warn: on_stop_event unexpected SLAVE STOP in state=SSIF_ABORTING
>>> ---
>>> v10:
>>> + None
>>>
>>> v9:
>>> + Fix dependence with I2C subsystem
>>> [Randy]
>>> + Remove useless error handling path
>>> [CJ]
>>> + Update comment for SSIF_ABORTING state
>>> [CJ]
>>> + Fix "unknown type name --u8" [kernel test
>>> robot]
>>> + Fix ssif_bmc_remove() to return void to align with recent kernel
>>> change [Quan]
>>>
>>> v8:
>>> + Dropped ssif_bmc.h file and move its content to ssif_bmc.c
>>> [Corey]
>>> + Add struct ipmi_ssif_msg to include/uapi/linux/ipmi_ssif_bmc.h
>>> header file [Corey]
>>> + Use unsigned int for len field in struct ipmi_ssif_msg
>>> [Corey]
>>> + Avoid using packed structure
>>> [Corey]
>>> + Add comment to clarify the logic flow
>>> [Corey]
>>> + Fix multipart read end with len=0 issue
>>> [Corey]
>>> + Refactor code handle the too big request message
>>> [Corey]
>>> + Fix code indentation issue
>>> [Corey]
>>> + Clean buffer before receiving request to avoid garbage
>>> [Quan]
>>> + Fix the license to SPDX-License-Identifier: GPL-2.0-only
>>> [Quan]
>>>
>>> v7:
>>> + Remove unneccessary del_timer() in response_timeout()
>>> [Corey]
>>> + Change compatible string from "ampere,ssif-bmc" to "ssif-bmc"
>>> [Jae]
>>> + Add MODULE_DEVICE_TABLE(of, ssif_bmc_match), fix blank line
>>> [Jae]
>>> + Dropped the use of ssif_msg_len() macro, use the len directly
>>> [Quan]
>>> + Solve possible issue if both response timer and ssif_bmc_write()
>>> occurred at the same time
>>> [Corey]
>>> + Fix wrong return type of ssif_bmc_poll() [kernel robot
>>> test]
>>> + Refactor and introduce ssif_part_buffer struct to replace the
>>> response_buf to manage each send/receive part of ssif
>>> [Quan]
>>> + Change SSIF_BAD_SMBUS state to SSIF_ABORTING state
>>> [Corey]
>>> + Support abort feature to skip the current bad request/response and
>>> wait until next new request
>>> [Corey]
>>> + Refactor the PEC calculation to avoid the re-calculate the PEC on
>>> each I2C_SLAVE_WRITE_RECEIVED event
>>> [Quan]
>>> + Fix the use of error-proned idx
>>> [Corey]
>>> + Defer the test for valid SMBus command until the read/write part
>>> is determined [Quan]
>>> + Change/split unsupported_smbus_cmd() to
>>> supported_[write|read]_cmd() [Corey]
>>> + Abort the request if somehow its size exceeded 255 bytes
>>> [Quan]
>>>
>>> v6:
>>> + Drop the use of slave_enable()
>>> [Wolfram]
>>> + Make i2c-aspeed to issue RxCmdLast command on all
>>> I2C_SLAVE_WRITE_REQUESTED event to assert NAK when slave busy
>>> [Quan]
>>> + Make i2c slave to return -EBUSY when it's busy
>>> [Quan]
>>> + Drop the aborting feature as return Completion Code 0xFF may stop
>>> host to retry and make ipmi_ssif.so fails to load
>>> [Quan]
>>> + Add timer to recover slave from busy state when no response
>>> [Quan]
>>> + Clean request/response buffer appropriately
>>> [Quan]
>>> + Add some minor change on error and warning messages
>>> [Quan]
>>>
>>> v5:
>>> + None
>>>
>>> v4:
>>> + Send response with Completion code 0xFF when aborting
>>> [Quan]
>>> + Added bounding check on SMBus writes and the whole request
>>> [Dan]
>>> + Moved buffer to end of struct ssif_bmc_ctx to avoid context
>>> corruption if somehow buffer is written past the end
>>> [Dan]
>>> + Return -EINVAL if userspace buffer too small, dont
>>> silence truncate [Corey, Joel]
>>> + Not necessary to check NONBLOCK in lock
>>> [Corey]
>>> + Enforce one user at a time
>>> [Joel]
>>> + Reject write with invalid response length from userspace
>>> [Corey]
>>> + Add state machines for better ssif bmc state handling
>>> [Quan]
>>> + Drop ssif_bmc_aspeed.c and make ssif_bmc.c is generic
>>> SSIF BMC driver
>>> [Quan]
>>> + Change compatible string "aspeed,ast2500-ssif-bmc" to
>>> "ampere,ssif-bmc" [Quan]
>>> + Abort current request with invalid SMBus write or
>>> invalid command
>>> [Quan]
>>> + Abort all request if there is pending response
>>> [Quan]
>>> + Changed validate_pec() to validate_request()
>>> [Quan]
>>> + Add unsupported_smbus_cmd() to handle unknown SMBus command
>>> [Quan]
>>> + Print internal state string for ease investigating issue
>>> [Quan]
>>> + Move to READY state on SLAVE_STOP event
>>> [Quan]
>>> + Change initilize_transfer() to process_smbus_cmd()
>>> [Quan]
>>> + Introduce functions for each slave event
>>> [Quan]
>>>
>>> v3:
>>> + Removed redundant license info
>>> [Joel]
>>> + Switched to use traditional if-else
>>> [Joel]
>>> + Removed unused ssif_bmc_ioctl()
>>> [Joel]
>>> + Made handle_request()/complete_response() to return void
>>> [Joel]
>>> + Refactored send_ssif_bmc_response() and
>>> receive_ssif_bmc_request() [Corey]
>>> + Removed mutex
>>> [Corey]
>>> + Use spin_lock/unlock_irqsave/restore in callback
>>> [Corey]
>>> + Removed the unnecessary memset
>>> [Corey]
>>> + Switch to use dev_err()
>>> [Corey]
>>>
>>> v2:
>>> + Fixed compiling error with COMPILE_TEST for arc
>>> ---
>>> drivers/char/ipmi/Kconfig | 10 +
>>> drivers/char/ipmi/Makefile | 1 +
>>> drivers/char/ipmi/ssif_bmc.c | 873
>>> +++++++++++++++++++++++++++++
>>> include/uapi/linux/ipmi_ssif_bmc.h | 18 +
>>> 4 files changed, 902 insertions(+)
>>> create mode 100644 drivers/char/ipmi/ssif_bmc.c
>>> create mode 100644 include/uapi/linux/ipmi_ssif_bmc.h
>>>
>>> diff --git a/drivers/char/ipmi/Kconfig b/drivers/char/ipmi/Kconfig
>>> index 39565cf74b2c..b6c0d35fc1a5 100644
>>> --- a/drivers/char/ipmi/Kconfig
>>> +++ b/drivers/char/ipmi/Kconfig
>>> @@ -169,6 +169,16 @@ config ASPEED_BT_IPMI_BMC
>>> found on Aspeed SOCs (AST2400 and AST2500). The driver
>>> implements the BMC side of the BT interface.
>>> +config SSIF_IPMI_BMC
>>> + tristate "SSIF IPMI BMC driver"
>>> + depends on I2C && I2C_SLAVE
>>> + help
>>> + This enables the IPMI SMBus system interface (SSIF) at the
>>> + management (BMC) side.
>>> +
>>> + The driver implements the BMC side of the SMBus system
>>> + interface (SSIF).
>>> +
>>> config IPMB_DEVICE_INTERFACE
>>> tristate 'IPMB Interface handler'
>>> depends on I2C
>>> diff --git a/drivers/char/ipmi/Makefile b/drivers/char/ipmi/Makefile
>>> index 7ce790efad92..cb6138b8ded9 100644
>>> --- a/drivers/char/ipmi/Makefile
>>> +++ b/drivers/char/ipmi/Makefile
>>> @@ -30,3 +30,4 @@ obj-$(CONFIG_ASPEED_BT_IPMI_BMC) += bt-bmc.o
>>> obj-$(CONFIG_ASPEED_KCS_IPMI_BMC) += kcs_bmc_aspeed.o
>>> obj-$(CONFIG_NPCM7XX_KCS_IPMI_BMC) += kcs_bmc_npcm7xx.o
>>> obj-$(CONFIG_IPMB_DEVICE_INTERFACE) += ipmb_dev_int.o
>>> +obj-$(CONFIG_SSIF_IPMI_BMC) += ssif_bmc.o
>>> diff --git a/drivers/char/ipmi/ssif_bmc.c
>>> b/drivers/char/ipmi/ssif_bmc.c
>>> new file mode 100644
>>> index 000000000000..a7bb4b99000e
>>> --- /dev/null
>>> +++ b/drivers/char/ipmi/ssif_bmc.c
>>> @@ -0,0 +1,873 @@
>>> +// SPDX-License-Identifier: GPL-2.0-only
>>> +/*
>>> + * The driver for BMC side of SSIF interface
>>> + *
>>> + * Copyright (c) 2022, Ampere Computing LLC
>>> + *
>>> + */
>>> +
>>> +#include <linux/i2c.h>
>>> +#include <linux/miscdevice.h>
>>> +#include <linux/module.h>
>>> +#include <linux/of.h>
>>> +#include <linux/platform_device.h>
>>> +#include <linux/poll.h>
>>> +#include <linux/sched.h>
>>> +#include <linux/mutex.h>
>>> +#include <linux/spinlock.h>
>>> +#include <linux/timer.h>
>>> +#include <linux/jiffies.h>
>>> +#include <linux/ipmi_ssif_bmc.h>
>>> +
>>> +#define DEVICE_NAME "ipmi-ssif-host"
>>> +
>>> +#define GET_8BIT_ADDR(addr_7bit) (((addr_7bit) << 1)
>>> & 0xff)
>>> +
>>> +/* A standard SMBus Transaction is limited to 32 data bytes */
>>> +#define MAX_PAYLOAD_PER_TRANSACTION 32
>>> +/* Transaction includes the address, the command, the length and
>>> the PEC byte */
>>> +#define MAX_TRANSACTION (MAX_PAYLOAD_PER_TRANSACTION + 4)
>>> +
>>> +#define MAX_IPMI_DATA_PER_START_TRANSACTION 30
>>> +#define MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION 31
>>> +
>>> +#define SSIF_IPMI_SINGLEPART_WRITE 0x2
>>> +#define SSIF_IPMI_SINGLEPART_READ 0x3
>>> +#define SSIF_IPMI_MULTIPART_WRITE_START 0x6
>>> +#define SSIF_IPMI_MULTIPART_WRITE_MIDDLE 0x7
>>> +#define SSIF_IPMI_MULTIPART_WRITE_END 0x8
>>> +#define SSIF_IPMI_MULTIPART_READ_START 0x3
>>> +#define SSIF_IPMI_MULTIPART_READ_MIDDLE 0x9
>>> +
>>> +/*
>>> + * IPMI 2.0 Spec, section 12.7 SSIF Timing,
>>> + * Request-to-Response Time is T6max(250ms) - T1max(20ms) - 3ms =
>>> 227ms
>>> + * Recover ssif_bmc from busy state if it takes up to 500ms
>>> + */
>>> +#define RESPONSE_TIMEOUT 500 /* ms */
>>> +
>>> +struct ssif_part_buffer {
>>> + u8 address;
>>> + u8 smbus_cmd;
>>> + u8 length;
>>> + u8 payload[MAX_PAYLOAD_PER_TRANSACTION];
>>> + u8 pec;
>>> + u8 index;
>>> +};
>>> +
>>> +/*
>>> + * SSIF internal states:
>>> + * SSIF_READY 0x00 : Ready state
>>> + * SSIF_START 0x01 : Start smbus transaction
>>> + * SSIF_SMBUS_CMD 0x02 : Received SMBus command
>>> + * SSIF_REQ_RECVING 0x03 : Receiving request
>>> + * SSIF_RES_SENDING 0x04 : Sending response
>>> + * SSIF_ABORTING 0x05 : Aborting state
>>> + */
>>> +enum ssif_state {
>>> + SSIF_READY,
>>> + SSIF_START,
>>> + SSIF_SMBUS_CMD,
>>> + SSIF_REQ_RECVING,
>>> + SSIF_RES_SENDING,
>>> + SSIF_ABORTING,
>>> + SSIF_STATE_MAX
>>> +};
>>> +
>>> +struct ssif_bmc_ctx {
>>> + struct i2c_client *client;
>>> + struct miscdevice miscdev;
>>> + int msg_idx;
>>> + bool pec_support;
>>> + /* ssif bmc spinlock */
>>> + spinlock_t lock;
>>> + wait_queue_head_t wait_queue;
>>> + u8 running;
>>> + enum ssif_state state;
>>> + /* Timeout waiting for response */
>>> + struct timer_list response_timer;
>>> + bool response_timer_inited;
>>> + /* Flag to identify a Multi-part Read Transaction */
>>> + bool is_singlepart_read;
>>> + u8 nbytes_processed;
>>> + u8 remain_len;
>>> + u8 recv_len;
>>> + /* Block Number of a Multi-part Read Transaction */
>>> + u8 block_num;
>>> + bool request_available;
>>> + bool response_in_progress;
>>> + bool busy;
>>> + bool aborting;
>>> + /* Buffer for SSIF Transaction part*/
>>> + struct ssif_part_buffer part_buf;
>>> + struct ipmi_ssif_msg response;
>>> + struct ipmi_ssif_msg request;
>>> +};
>>> +
>>> +static inline struct ssif_bmc_ctx *to_ssif_bmc(struct file *file)
>>> +{
>>> + return container_of(file->private_data, struct ssif_bmc_ctx,
>>> miscdev);
>>> +}
>>> +
>>> +static const char *state_to_string(enum ssif_state state)
>>> +{
>>> + switch (state) {
>>> + case SSIF_READY:
>>> + return "SSIF_READY";
>>> + case SSIF_START:
>>> + return "SSIF_START";
>>> + case SSIF_SMBUS_CMD:
>>> + return "SSIF_SMBUS_CMD";
>>> + case SSIF_REQ_RECVING:
>>> + return "SSIF_REQ_RECVING";
>>> + case SSIF_RES_SENDING:
>>> + return "SSIF_RES_SENDING";
>>> + case SSIF_ABORTING:
>>> + return "SSIF_ABORTING";
>>> + default:
>>> + return "SSIF_STATE_UNKNOWN";
>>> + }
>>> +}
>>> +
>>> +/* Handle SSIF message that will be sent to user */
>>> +static ssize_t ssif_bmc_read(struct file *file, char __user *buf,
>>> size_t count, loff_t *ppos)
>>> +{
>>> + struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
>>> + struct ipmi_ssif_msg msg;
>>> + unsigned long flags;
>>> + ssize_t ret;
>>> +
>>> + spin_lock_irqsave(&ssif_bmc->lock, flags);
>>> + while (!ssif_bmc->request_available) {
>>> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
>>> + if (file->f_flags & O_NONBLOCK)
>>> + return -EAGAIN;
>>> + ret = wait_event_interruptible(ssif_bmc->wait_queue,
>>> + ssif_bmc->request_available);
>>> + if (ret)
>>> + return ret;
>>> + spin_lock_irqsave(&ssif_bmc->lock, flags);
>>> + }
>>> +
>>> + if (count < min_t(ssize_t,
>>> + sizeof_field(struct ipmi_ssif_msg, len) +
>>> ssif_bmc->request.len,
>>> + sizeof(struct ipmi_ssif_msg))) {
>>> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
>>> + ret = -EINVAL;
>>> + } else {
>>> + count = min_t(ssize_t,
>>> + sizeof_field(struct ipmi_ssif_msg, len) +
>>> ssif_bmc->request.len,
>>> + sizeof(struct ipmi_ssif_msg));
>>> + memcpy(&msg, &ssif_bmc->request, count);
>>> + ssif_bmc->request_available = false;
>>> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
>>> +
>>> + ret = copy_to_user(buf, &msg, count);
>>> + }
>>> +
>>> + return (ret < 0) ? ret : count;
>>> +}
>>> +
>>> +/* Handle SSIF message that is written by user */
>>> +static ssize_t ssif_bmc_write(struct file *file, const char __user
>>> *buf, size_t count,
>>> + loff_t *ppos)
>>> +{
>>> + struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
>>> + struct ipmi_ssif_msg msg;
>>> + unsigned long flags;
>>> + ssize_t ret;
>>> +
>>> + if (count > sizeof(struct ipmi_ssif_msg))
>>> + return -EINVAL;
>>> +
>>> + if (copy_from_user(&msg, buf, count))
>>> + return -EFAULT;
>>> +
>>> + if (!msg.len || count < sizeof_field(struct ipmi_ssif_msg, len)
>>> + msg.len)
>>> + return -EINVAL;
>>> +
>>> + spin_lock_irqsave(&ssif_bmc->lock, flags);
>>> + while (ssif_bmc->response_in_progress) {
>>> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
>>> + if (file->f_flags & O_NONBLOCK)
>>> + return -EAGAIN;
>>> + ret = wait_event_interruptible(ssif_bmc->wait_queue,
>>> + !ssif_bmc->response_in_progress);
>>> + if (ret)
>>> + return ret;
>>> + spin_lock_irqsave(&ssif_bmc->lock, flags);
>>> + }
>>> +
>>> + /*
>>> + * The write must complete before the response timeout fired,
>>> otherwise
>>> + * the response is aborted and wait for next request
>>> + * Return -EINVAL if the response is aborted
>>> + */
>>> + ret = (ssif_bmc->response_timer_inited) ? 0 : -EINVAL;
>>> + if (ret)
>>> + goto exit;
>>> +
>>> + del_timer(&ssif_bmc->response_timer);
>>> + ssif_bmc->response_timer_inited = false;
>>> +
>>> + memcpy(&ssif_bmc->response, &msg, count);
>>> + ssif_bmc->is_singlepart_read = (msg.len <=
>>> MAX_PAYLOAD_PER_TRANSACTION);
>>> +
>>> + ssif_bmc->response_in_progress = true;
>>> +
>>> + /* ssif_bmc not busy */
>>> + ssif_bmc->busy = false;
>>> +
>>> + /* Clean old request buffer */
>>> + memset(&ssif_bmc->request, 0, sizeof(struct ipmi_ssif_msg));
>>> +exit:
>>> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
>>> +
>>> + return (ret < 0) ? ret : count;
>>> +}
>>> +
>>> +static int ssif_bmc_open(struct inode *inode, struct file *file)
>>> +{
>>> + struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
>>> + int ret = 0;
>>> +
>>> + spin_lock_irq(&ssif_bmc->lock);
>>> + if (!ssif_bmc->running)
>>> + ssif_bmc->running = 1;
>>> + else
>>> + ret = -EBUSY;
>>> + spin_unlock_irq(&ssif_bmc->lock);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +static __poll_t ssif_bmc_poll(struct file *file, poll_table *wait)
>>> +{
>>> + struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
>>> + __poll_t mask = 0;
>>> +
>>> + poll_wait(file, &ssif_bmc->wait_queue, wait);
>>> +
>>> + spin_lock_irq(&ssif_bmc->lock);
>>> + /* The request is available, userspace application can get the
>>> request */
>>> + if (ssif_bmc->request_available)
>>> + mask |= POLLIN;
>>> +
>>> + spin_unlock_irq(&ssif_bmc->lock);
>>> +
>>> + return mask;
>>> +}
>>> +
>>> +static int ssif_bmc_release(struct inode *inode, struct file *file)
>>> +{
>>> + struct ssif_bmc_ctx *ssif_bmc = to_ssif_bmc(file);
>>> +
>>> + spin_lock_irq(&ssif_bmc->lock);
>>> + ssif_bmc->running = 0;
>>> + spin_unlock_irq(&ssif_bmc->lock);
>>> +
>>> + return 0;
>>> +}
>>> +
>>> +/*
>>> + * System calls to device interface for user apps
>>> + */
>>> +static const struct file_operations ssif_bmc_fops = {
>>> + .owner = THIS_MODULE,
>>> + .open = ssif_bmc_open,
>>> + .read = ssif_bmc_read,
>>> + .write = ssif_bmc_write,
>>> + .release = ssif_bmc_release,
>>> + .poll = ssif_bmc_poll,
>>> +};
>>> +
>>> +/* Called with ssif_bmc->lock held. */
>>> +static void complete_response(struct ssif_bmc_ctx *ssif_bmc)
>>> +{
>>> + /* Invalidate response in buffer to denote it having been sent. */
>>> + ssif_bmc->response.len = 0;
>>> + ssif_bmc->response_in_progress = false;
>>> + ssif_bmc->nbytes_processed = 0;
>>> + ssif_bmc->remain_len = 0;
>>> + ssif_bmc->busy = false;
>>> + memset(&ssif_bmc->part_buf, 0, sizeof(struct ssif_part_buffer));
>>> + wake_up_all(&ssif_bmc->wait_queue);
>>> +}
>>> +
>>> +static void response_timeout(struct timer_list *t)
>>> +{
>>> + struct ssif_bmc_ctx *ssif_bmc = from_timer(ssif_bmc, t,
>>> response_timer);
>>> + unsigned long flags;
>>> +
>>> + spin_lock_irqsave(&ssif_bmc->lock, flags);
>>> +
>>> + /* Do nothing if the response is in progress */
>>> + if (!ssif_bmc->response_in_progress) {
>>> + /* Recover ssif_bmc from busy */
>>> + ssif_bmc->busy = false;
>>> + ssif_bmc->response_timer_inited = false;
>>> + /* Set aborting flag */
>>> + ssif_bmc->aborting = true;
>>> + }
>>> +
>>> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
>>> +}
>>> +
>>> +/* Called with ssif_bmc->lock held. */
>>> +static void handle_request(struct ssif_bmc_ctx *ssif_bmc)
>>> +{
>>> + /* set ssif_bmc to busy waiting for response */
>>> + ssif_bmc->busy = true;
>>> + /* Request message is available to process */
>>> + ssif_bmc->request_available = true;
>>> + /* Clean old response buffer */
>>> + memset(&ssif_bmc->response, 0, sizeof(struct ipmi_ssif_msg));
>>> + /* This is the new READ request.*/
>>> + wake_up_all(&ssif_bmc->wait_queue);
>>> +
>>> + /* Armed timer to recover slave from busy state in case of no
>>> response */
>>> + if (!ssif_bmc->response_timer_inited) {
>>> + timer_setup(&ssif_bmc->response_timer, response_timeout, 0);
>>> + ssif_bmc->response_timer_inited = true;
>>> + }
>>> + mod_timer(&ssif_bmc->response_timer, jiffies +
>>> msecs_to_jiffies(RESPONSE_TIMEOUT));
>>> +}
>>> +
>>> +static void calculate_response_part_pec(struct ssif_part_buffer *part)
>>> +{
>>> + u8 addr = part->address;
>>> +
>>> + /* PEC - Start Read Address */
>>> + part->pec = i2c_smbus_pec(0, &addr, 1);
>>> + /* PEC - SSIF Command */
>>> + part->pec = i2c_smbus_pec(part->pec, &part->smbus_cmd, 1);
>>> + /* PEC - Restart Write Address */
>>> + addr = addr | 0x01;
>>> + part->pec = i2c_smbus_pec(part->pec, &addr, 1);
>>> + part->pec = i2c_smbus_pec(part->pec, &part->length, 1);
>>> + if (part->length)
>>> + part->pec = i2c_smbus_pec(part->pec, part->payload,
>>> part->length);
>>> +}
>>> +
>>> +static void set_singlepart_response_buffer(struct ssif_bmc_ctx
>>> *ssif_bmc)
>>> +{
>>> + struct ssif_part_buffer *part = &ssif_bmc->part_buf;
>>> +
>>> + part->address = GET_8BIT_ADDR(ssif_bmc->client->addr);
>>> + part->length = (u8)ssif_bmc->response.len;
>>> +
>>> + /* Clear the rest to 0 */
>>> + memset(part->payload + part->length, 0,
>>> MAX_PAYLOAD_PER_TRANSACTION - part->length);
>>> + memcpy(&part->payload[0], &ssif_bmc->response.payload[0],
>>> part->length);
>>> +}
>>> +
>>> +static void set_multipart_response_buffer(struct ssif_bmc_ctx
>>> *ssif_bmc)
>>> +{
>>> + struct ssif_part_buffer *part = &ssif_bmc->part_buf;
>>> + u8 part_len = 0;
>>> +
>>> + part->address = GET_8BIT_ADDR(ssif_bmc->client->addr);
>>> + switch (part->smbus_cmd) {
>>> + case SSIF_IPMI_MULTIPART_READ_START:
>>> + /*
>>> + * Read Start length is 32 bytes.
>>> + * Read Start transfer first 30 bytes of IPMI response
>>> + * and 2 special code 0x00, 0x01.
>>> + */
>>> + ssif_bmc->nbytes_processed = 0;
>>> + ssif_bmc->block_num = 0;
>>> + part->length = MAX_PAYLOAD_PER_TRANSACTION;
>>> + part_len = MAX_IPMI_DATA_PER_START_TRANSACTION;
>>> + ssif_bmc->remain_len = ssif_bmc->response.len - part_len;
>>> +
>>> + part->payload[0] = 0x00; /* Start Flag */
>>> + part->payload[1] = 0x01; /* Start Flag */
>>> +
>>> + memcpy(&part->payload[2], &ssif_bmc->response.payload[0],
>>> part_len);
>>> + break;
>>> +
>>> + case SSIF_IPMI_MULTIPART_READ_MIDDLE:
>>> + /*
>>> + * IPMI READ Middle or READ End messages can carry up to 31
>>> bytes
>>> + * IPMI data plus block number byte.
>>> + */
>>> + if (ssif_bmc->remain_len <=
>>> MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION) {
>>> + /*
>>> + * This is READ End message
>>> + * Return length is the remaining response data length
>>> + * plus block number
>>> + * Block number 0xFF is to indicate this is last message
>>> + *
>>> + */
>>> + /* Clean the buffer */
>>> + memset(&part->payload[0], 0, MAX_PAYLOAD_PER_TRANSACTION);
>>> + part->length = ssif_bmc->remain_len + 1;
>>> + part_len = ssif_bmc->remain_len;
>>> + ssif_bmc->block_num = 0xFF;
>>> + part->payload[0] = ssif_bmc->block_num;
>>> + } else {
>>> + /*
>>> + * This is READ Middle message
>>> + * Response length is the maximum SMBUS transfer length
>>> + * Block number byte is incremented
>>> + * Return length is maximum SMBUS transfer length
>>> + */
>>> + part->length = MAX_PAYLOAD_PER_TRANSACTION;
>>> + part_len = MAX_IPMI_DATA_PER_MIDDLE_TRANSACTION;
>>> + part->payload[0] = ssif_bmc->block_num;
>>> + ssif_bmc->block_num++;
>>> + }
>>> +
>>> + ssif_bmc->remain_len -= part_len;
>>> + memcpy(&part->payload[1], ssif_bmc->response.payload +
>>> ssif_bmc->nbytes_processed,
>>> + part_len);
>>> + break;
>>> +
>>> + default:
>>> + /* Do not expect to go to this case */
>>> + dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus
>>> command 0x%x\n",
>>> + __func__, part->smbus_cmd);
>>> + break;
>>> + }
>>> +
>>> + ssif_bmc->nbytes_processed += part_len;
>>> +}
>>> +
>>> +static bool supported_read_cmd(u8 cmd)
>>> +{
>>> + if (cmd == SSIF_IPMI_SINGLEPART_READ ||
>>> + cmd == SSIF_IPMI_MULTIPART_READ_START ||
>>> + cmd == SSIF_IPMI_MULTIPART_READ_MIDDLE)
>>> + return true;
>>> +
>>> + return false;
>>> +}
>>> +
>>> +static bool supported_write_cmd(u8 cmd)
>>> +{
>>> + if (cmd == SSIF_IPMI_SINGLEPART_WRITE ||
>>> + cmd == SSIF_IPMI_MULTIPART_WRITE_START ||
>>> + cmd == SSIF_IPMI_MULTIPART_WRITE_MIDDLE ||
>>> + cmd == SSIF_IPMI_MULTIPART_WRITE_END)
>>> + return true;
>>> +
>>> + return false;
>>> +}
>>> +
>>> +/* Process the IPMI response that will be read by master */
>>> +static void handle_read_processed(struct ssif_bmc_ctx *ssif_bmc, u8
>>> *val)
>>> +{
>>> + struct ssif_part_buffer *part = &ssif_bmc->part_buf;
>>> +
>>> + /* msg_idx start from 0 */
>>> + if (part->index < part->length)
>>> + *val = part->payload[part->index];
>>> + else if (part->index == part->length && ssif_bmc->pec_support)
>>> + *val = part->pec;
>>> + else
>>> + *val = 0;
>>> +
>>> + part->index++;
>>> +}
>>> +
>>> +static void handle_write_received(struct ssif_bmc_ctx *ssif_bmc, u8
>>> *val)
>>> +{
>>> + /*
>>> + * The msg_idx must be 1 when first enter SSIF_REQ_RECVING state
>>> + * And it would never exceeded 36 bytes included the 32 bytes
>>> max payload +
>>> + * the address + the command + the len and the PEC.
>>> + */
>>> + if (ssif_bmc->msg_idx < 1 || ssif_bmc->msg_idx > MAX_TRANSACTION)
>>> + return;
>>> +
>>> + if (ssif_bmc->msg_idx == 1) {
>>> + ssif_bmc->part_buf.length = *val;
>>> + ssif_bmc->part_buf.index = 0;
>>> + } else {
>>> + ssif_bmc->part_buf.payload[ssif_bmc->part_buf.index++] = *val;
>>> + }
>>> +
>>> + ssif_bmc->msg_idx++;
>>> +}
>>> +
>>> +static bool validate_request_part(struct ssif_bmc_ctx *ssif_bmc)
>>> +{
>>> + struct ssif_part_buffer *part = &ssif_bmc->part_buf;
>>> + bool ret = true;
>>> + u8 cpec;
>>> + u8 addr;
>>> +
>>> + if (part->index == part->length) {
>>> + /* PEC is not included */
>>> + ssif_bmc->pec_support = false;
>>> + ret = true;
>>> + goto exit;
>>> + }
>>> +
>>> + if (part->index != part->length + 1) {
>>> + ret = false;
>>> + goto exit;
>>> + }
>>> +
>>> + /* PEC is included */
>>> + ssif_bmc->pec_support = true;
>>> + part->pec = part->payload[part->length];
>>> + addr = GET_8BIT_ADDR(ssif_bmc->client->addr);
>>> + cpec = i2c_smbus_pec(0, &addr, 1);
>>> + cpec = i2c_smbus_pec(cpec, &part->smbus_cmd, 1);
>>> + cpec = i2c_smbus_pec(cpec, &part->length, 1);
>>> + /*
>>> + * As SMBus specification does not allow the length
>>> + * (byte count) in the Write-Block protocol to be zero.
>>> + * Therefore, it is illegal to have the last Middle
>>> + * transaction in the sequence carry 32-byte and have
>>> + * a length of ‘0’ in the End transaction.
>>> + * But some users may try to use this way and we should
>>> + * prevent ssif_bmc driver broken in this case.
>>> + */
>>> + if (part->length)
>>> + cpec = i2c_smbus_pec(cpec, part->payload, part->length);
>>> +
>>> + if (cpec != part->pec)
>>> + ret = false;
>>> +
>>> +exit:
>>> + return ret;
>>> +}
>>> +
>>> +static void process_request_part(struct ssif_bmc_ctx *ssif_bmc)
>>> +{
>>> + struct ssif_part_buffer *part = &ssif_bmc->part_buf;
>>> + unsigned int len;
>>> +
>>> + switch (part->smbus_cmd) {
>>> + case SSIF_IPMI_SINGLEPART_WRITE:
>>> + /* save the whole part to request*/
>>> + ssif_bmc->request.len = part->length;
>>> + memcpy(ssif_bmc->request.payload, part->payload,
>>> part->length);
>>> +
>>> + break;
>>> + case SSIF_IPMI_MULTIPART_WRITE_START:
>>> + ssif_bmc->request.len = 0;
>>> +
>>> + fallthrough;
>>> + case SSIF_IPMI_MULTIPART_WRITE_MIDDLE:
>>> + case SSIF_IPMI_MULTIPART_WRITE_END:
>>> + len = ssif_bmc->request.len + part->length;
>>> + /* Do the bound check here, not allow the request len
>>> exceed 254 bytes */
>>> + if (len > IPMI_SSIF_PAYLOAD_MAX) {
>>> + dev_warn(&ssif_bmc->client->dev,
>>> + "Warn: Request exceeded 254 bytes, aborting");
>>> + /* Request too long, aborting */
>>> + ssif_bmc->aborting = true;
>>> + } else {
>>> + memcpy(ssif_bmc->request.payload + ssif_bmc->request.len,
>>> + part->payload, part->length);
>>> + ssif_bmc->request.len += part->length;
>>> + }
>>> + break;
>>> + default:
>>> + /* Do not expect to go to this case */
>>> + dev_err(&ssif_bmc->client->dev, "%s: Unexpected SMBus
>>> command 0x%x\n",
>>> + __func__, part->smbus_cmd);
>>> + break;
>>> + }
>>> +}
>>> +
>>> +static void process_smbus_cmd(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
>>> +{
>>> + /* SMBUS command can vary (single or multi-part) */
>>> + ssif_bmc->part_buf.smbus_cmd = *val;
>>> + ssif_bmc->msg_idx = 1;
>>> + memset(&ssif_bmc->part_buf.payload[0], 0,
>>> MAX_PAYLOAD_PER_TRANSACTION);
>>> +
>>> + if (*val == SSIF_IPMI_SINGLEPART_WRITE || *val ==
>>> SSIF_IPMI_MULTIPART_WRITE_START) {
>>> + /*
>>> + * The response maybe not come in-time, causing host SSIF
>>> driver
>>> + * to timeout and resend a new request. In such case check for
>>> + * pending response and clear it
>>> + */
>>> + if (ssif_bmc->response_in_progress)
>>> + complete_response(ssif_bmc);
>>> +
>>> + /* This is new request, flip aborting flag if set */
>>> + if (ssif_bmc->aborting)
>>> + ssif_bmc->aborting = false;
>>> + }
>>> +}
>>> +
>>> +static void on_read_requested_event(struct ssif_bmc_ctx *ssif_bmc,
>>> u8 *val)
>>> +{
>>> + if (ssif_bmc->state == SSIF_READY ||
>> Is this actually correct? The state machine seems to set this as the
>> default state and in my testing we seem to always reach here with the
>> state == SSIF_READY?
>
> The I2C_SLAVE_READ_REQUESTED event is expected to come on
> SSIF_SMBUS_CMD state where Slave has already received and validated
> the SMBus command, in this case is the I2C_SLAVE_READ_REQUESTED event
> if the SMBus command indeed is the READ command. You can see the check
> supported_read_cmd() below.
>
> If Slave see the I2C_SLAVE_READ_REQUESTED event on other states, it
> will transition to SSIF_ABORTING state that discard everything until
> there is a new transaction come.
>
> On READ, the sequence of Slave event should be as below:
> I2C_SLAVE_WRITE_REQUESTED (addr) => I2C_SLAVE_WRITE_RECEIVED (SMBus
> cmd) => I2C_SLAVE_READ_REQUESTED (Slave feed the first byte) =>
> I2C_SLAVE_READ_PROCESSED (Slave 2nd byte) => .... => I2C_SLAVE_STOP
>
>>> + ssif_bmc->state == SSIF_START ||
>>> + ssif_bmc->state == SSIF_REQ_RECVING ||
>>> + ssif_bmc->state == SSIF_RES_SENDING) {
>>> + dev_warn(&ssif_bmc->client->dev,
>>> + "Warn: %s unexpected READ REQUESTED in state=%s\n",
>>> + __func__, state_to_string(ssif_bmc->state));
>>> + ssif_bmc->state = SSIF_ABORTING;
>>> + *val = 0;
>>> + return;
>>> +
>>> + } else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
>>> + if (!supported_read_cmd(ssif_bmc->part_buf.smbus_cmd)) {
>>> + dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus
>>> read command=0x%x",
>>> + ssif_bmc->part_buf.smbus_cmd);
>>> + ssif_bmc->aborting = true;
>>> + }
>>> +
>>> + if (ssif_bmc->aborting)
>>> + ssif_bmc->state = SSIF_ABORTING;
>>> + else
>>> + ssif_bmc->state = SSIF_RES_SENDING;
>>> + }
>>> +
>>> + ssif_bmc->msg_idx = 0;
>>> +
>>> + /* Send 0 if there is nothing to send */
>>> + if (!ssif_bmc->response_in_progress || ssif_bmc->state ==
>>> SSIF_ABORTING) {
>>> + *val = 0;
>>> + return;
>>> + }
>>> +
>>> + if (ssif_bmc->is_singlepart_read)
>>> + set_singlepart_response_buffer(ssif_bmc);
>>> + else
>>> + set_multipart_response_buffer(ssif_bmc);
>>> +
>>> + calculate_response_part_pec(&ssif_bmc->part_buf);
>>> + ssif_bmc->part_buf.index = 0;
>>> + *val = ssif_bmc->part_buf.length;
>>> +}
>>> +
>>> +static void on_read_processed_event(struct ssif_bmc_ctx *ssif_bmc,
>>> u8 *val)
>>> +{
>>> + if (ssif_bmc->state == SSIF_READY ||
>> Same comment as above?
>
> Same here, I2C_SLAVE_READ_PROCESSED is expected to come after the
> I2C_SLAVE_READ_REQUESTED or other I2C_SLAVE_READ_PROCESSED. ie: when
> the state is SSIF_RES_SENDING.
> If it comes when Slave in states other than SSIF_RES_SENDING, the
> Slave will transition to SSIF_ABORTING state.
>
>>> + ssif_bmc->state == SSIF_START ||
>>> + ssif_bmc->state == SSIF_REQ_RECVING ||
>>> + ssif_bmc->state == SSIF_SMBUS_CMD) {
>>> + dev_warn(&ssif_bmc->client->dev,
>>> + "Warn: %s unexpected READ PROCESSED in state=%s\n",
>>> + __func__, state_to_string(ssif_bmc->state));
>>> + ssif_bmc->state = SSIF_ABORTING;
>>> + *val = 0;
>>> + return;
>>> + }
>>> +
>>> + /* Send 0 if there is nothing to send */
>>> + if (!ssif_bmc->response_in_progress || ssif_bmc->state ==
>>> SSIF_ABORTING) {
>>> + *val = 0;
>>> + return;
>>> + }
>>> +
>>> + handle_read_processed(ssif_bmc, val);
>>> +}
>>> +
>>> +static void on_write_requested_event(struct ssif_bmc_ctx *ssif_bmc,
>>> u8 *val)
>>> +{
>>> + if (ssif_bmc->state == SSIF_READY || ssif_bmc->state ==
>>> SSIF_SMBUS_CMD) {
>>> + ssif_bmc->state = SSIF_START;
>>> +
>>> + } else if (ssif_bmc->state == SSIF_START ||
>>> + ssif_bmc->state == SSIF_REQ_RECVING ||
>>> + ssif_bmc->state == SSIF_RES_SENDING) {
>>> + dev_warn(&ssif_bmc->client->dev,
>>> + "Warn: %s unexpected WRITE REQUEST in state=%s\n",
>>> + __func__, state_to_string(ssif_bmc->state));
>>> + ssif_bmc->state = SSIF_ABORTING;
>>> + return;
>>> + }
>>> +
>>> + ssif_bmc->msg_idx = 0;
>>> + ssif_bmc->part_buf.address = *val;
>>> +}
>>> +
>>> +static void on_write_received_event(struct ssif_bmc_ctx *ssif_bmc,
>>> u8 *val)
>>> +{
>>> + if (ssif_bmc->state == SSIF_READY ||
>>> + ssif_bmc->state == SSIF_RES_SENDING) {
>>> + dev_warn(&ssif_bmc->client->dev,
>>> + "Warn: %s unexpected WRITE RECEIVED in state=%s\n",
>>> + __func__, state_to_string(ssif_bmc->state));
>>> + ssif_bmc->state = SSIF_ABORTING;
>>> +
>>> + } else if (ssif_bmc->state == SSIF_START) {
>>> + ssif_bmc->state = SSIF_SMBUS_CMD;
>>> +
>>> + } else if (ssif_bmc->state == SSIF_SMBUS_CMD) {
>>> + if (!supported_write_cmd(ssif_bmc->part_buf.smbus_cmd)) {
>>> + dev_warn(&ssif_bmc->client->dev, "Warn: Unknown SMBus
>>> write command=0x%x",
>>> + ssif_bmc->part_buf.smbus_cmd);
>>> + ssif_bmc->aborting = true;
>>> + }
>>> +
>>> + if (ssif_bmc->aborting)
>>> + ssif_bmc->state = SSIF_ABORTING;
>>> + else
>>> + ssif_bmc->state = SSIF_REQ_RECVING;
>>> + }
>>> +
>>> + /* This is response sending state */
>>> + if (ssif_bmc->state == SSIF_REQ_RECVING)
>>> + handle_write_received(ssif_bmc, val);
>>> + else if (ssif_bmc->state == SSIF_SMBUS_CMD)
>>> + process_smbus_cmd(ssif_bmc, val);
>>> +}
>>> +
>>> +static void on_stop_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
>>> +{
>>> + if (ssif_bmc->state == SSIF_READY ||
>>> + ssif_bmc->state == SSIF_START ||
>>> + ssif_bmc->state == SSIF_SMBUS_CMD ||
>>> + ssif_bmc->state == SSIF_ABORTING) {
>>> + dev_warn(&ssif_bmc->client->dev,
>>> + "Warn: %s unexpected SLAVE STOP in state=%s\n",
>>> + __func__, state_to_string(ssif_bmc->state));
>>> + ssif_bmc->state = SSIF_READY;
>>> +
>>> + } else if (ssif_bmc->state == SSIF_REQ_RECVING) {
>>> + if (validate_request_part(ssif_bmc)) {
>>> + process_request_part(ssif_bmc);
>>> + if (ssif_bmc->part_buf.smbus_cmd ==
>>> SSIF_IPMI_SINGLEPART_WRITE ||
>>> + ssif_bmc->part_buf.smbus_cmd ==
>>> SSIF_IPMI_MULTIPART_WRITE_END)
>>> + handle_request(ssif_bmc);
>>> + ssif_bmc->state = SSIF_READY;
>>> + } else {
>>> + /*
>>> + * A BMC that receives an invalid request drop the data
>>> for the write
>>> + * transaction and any further transactions (read or
>>> write) until
>>> + * the next valid read or write Start transaction is
>>> received
>>> + */
>>> + dev_err(&ssif_bmc->client->dev, "Error: invalid pec\n");
>>> + ssif_bmc->aborting = true;
>>> + }
>>> + } else if (ssif_bmc->state == SSIF_RES_SENDING) {
>>> + if (ssif_bmc->is_singlepart_read || ssif_bmc->block_num ==
>>> 0xFF)
>>> + /* Invalidate response buffer to denote it is sent */
>>> + complete_response(ssif_bmc);
>>> + ssif_bmc->state = SSIF_READY;
>>> + }
>>> +
>>> + /* Reset message index */
>>> + ssif_bmc->msg_idx = 0;
>>> +}
>>> +
>>> +/*
>>> + * Callback function to handle I2C slave events
>>> + */
>>> +static int ssif_bmc_cb(struct i2c_client *client, enum
>>> i2c_slave_event event, u8 *val)
>>> +{
>>> + unsigned long flags;
>>> + struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
>>> + int ret = 0;
>>> +
>>> + spin_lock_irqsave(&ssif_bmc->lock, flags);
>>> +
>>> + switch (event) {
>>> + case I2C_SLAVE_READ_REQUESTED:
>>> + on_read_requested_event(ssif_bmc, val);
>>> + break;
>>> +
>>> + case :
>>> + on_write_requested_event(ssif_bmc, val);
>>> + break;
>>> +
>>> + case I2C_SLAVE_READ_PROCESSED:
>>> + on_read_processed_event(ssif_bmc, val);
>>> + break;
>>> +
>>> + case I2C_SLAVE_WRITE_RECEIVED:
>>> + on_write_received_event(ssif_bmc, val);
>>> + break;
>>> +
>>> + case I2C_SLAVE_STOP:
>>> + on_stop_event(ssif_bmc, val);
>>> + break;
>>> +
>>> + default:
>>> + dev_warn(&ssif_bmc->client->dev, "Warn: Unknown i2c slave
>>> event\n");
>>> + break;
>>> + }
>>> +
>>> + if (!ssif_bmc->aborting && ssif_bmc->busy)
>>> + ret = -EBUSY;
>>> +
>>> + spin_unlock_irqrestore(&ssif_bmc->lock, flags);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +static int ssif_bmc_probe(struct i2c_client *client, const struct
>>> i2c_device_id *id)
>>> +{
>>> + struct ssif_bmc_ctx *ssif_bmc;
>>> + int ret;
>>> +
>>> + ssif_bmc = devm_kzalloc(&client->dev, sizeof(*ssif_bmc),
>>> GFP_KERNEL);
>>> + if (!ssif_bmc)
>>> + return -ENOMEM;
>>> +
>>> + spin_lock_init(&ssif_bmc->lock);
>>> +
>>> + init_waitqueue_head(&ssif_bmc->wait_queue);
>>> + ssif_bmc->request_available = false;
>>> + ssif_bmc->response_in_progress = false;
>>> + ssif_bmc->busy = false;
>>> + ssif_bmc->response_timer_inited = false;
>>> +
>>> + /* Register misc device interface */
>>> + ssif_bmc->miscdev.minor = MISC_DYNAMIC_MINOR;
>>> + ssif_bmc->miscdev.name = DEVICE_NAME;
>>> + ssif_bmc->miscdev.fops = &ssif_bmc_fops;
>>> + ssif_bmc->miscdev.parent = &client->dev;
>>> + ret = misc_register(&ssif_bmc->miscdev);
>>> + if (ret)
>>> + return ret;
>>> +
>>> + ssif_bmc->client = client;
>>> + ssif_bmc->client->flags |= I2C_CLIENT_SLAVE;
>>> +
>>> + /* Register I2C slave */
>>> + i2c_set_clientdata(client, ssif_bmc);
>>> + ret = i2c_slave_register(client, ssif_bmc_cb);
>>> + if (ret)
>>> + misc_deregister(&ssif_bmc->miscdev);
>>> +
>>> + return ret;
>>> +}
>>> +
>>> +static void ssif_bmc_remove(struct i2c_client *client)
>>> +{
>>> + struct ssif_bmc_ctx *ssif_bmc = i2c_get_clientdata(client);
>>> +
>>> + i2c_slave_unregister(client);
>>> + misc_deregister(&ssif_bmc->miscdev);
>>> +}
>>> +
>>> +static const struct of_device_id ssif_bmc_match[] = {
>>> + { .compatible = "ssif-bmc" },
>>> + { },
>>> +};
>>> +MODULE_DEVICE_TABLE(of, ssif_bmc_match);
>>> +
>>> +static const struct i2c_device_id ssif_bmc_id[] = {
>>> + { DEVICE_NAME, 0 },
>>> + { },
>>> +};
>>> +MODULE_DEVICE_TABLE(i2c, ssif_bmc_id);
>>> +
>>> +static struct i2c_driver ssif_bmc_driver = {
>>> + .driver = {
>>> + .name = DEVICE_NAME,
>>> + .of_match_table = ssif_bmc_match,
>>> + },
>>> + .probe = ssif_bmc_probe,
>>> + .remove = ssif_bmc_remove,
>>> + .id_table = ssif_bmc_id,
>>> +};
>>> +
>>> +module_i2c_driver(ssif_bmc_driver);
>>> +
>>> +MODULE_AUTHOR("Quan Nguyen <quan at os.amperecomputing.com>");
>>> +MODULE_AUTHOR("Chuong Tran <chuong at os.amperecomputing.com>");
>>> +MODULE_DESCRIPTION("Linux device driver of the BMC IPMI SSIF
>>> interface.");
>>> +MODULE_LICENSE("GPL");
>>> diff --git a/include/uapi/linux/ipmi_ssif_bmc.h
>>> b/include/uapi/linux/ipmi_ssif_bmc.h
>>> new file mode 100644
>>> index 000000000000..1c6a753dad08
>>> --- /dev/null
>>> +++ b/include/uapi/linux/ipmi_ssif_bmc.h
>>> @@ -0,0 +1,18 @@
>>> +/* SPDX-License-Identifier: GPL-2.0-only WITH Linux-syscall-note*/
>>> +/*
>>> + * Copyright (c) 2022, Ampere Computing LLC.
>>> + */
>>> +
>>> +#ifndef _UAPI_LINUX_IPMI_SSIF_BMC_H
>>> +#define _UAPI_LINUX_IPMI_SSIF_BMC_H
>>> +
>>> +#include <linux/types.h>
>>> +
>>> +/* Max length of ipmi ssif message included netfn and cmd field */
>>> +#define IPMI_SSIF_PAYLOAD_MAX 254
>>> +struct ipmi_ssif_msg {
>>> + unsigned int len;
>>> + __u8 payload[IPMI_SSIF_PAYLOAD_MAX];
>>> +};
>>> +
>>> +#endif /* _UAPI_LINUX_IPMI_SSIF_BMC_H */
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