Move smbus_cmd assignment to the end of process_smbus_cmd() to ensure
the new command is not lost when complete_response() is triggered.

Fixes: dd2bc5cc9e25 ("ipmi: ssif_bmc: Add SSIF BMC driver")
Signed-off-by: Cosmo Chou <chou.cosmo@gmail.com>
---
 drivers/char/ipmi/ssif_bmc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
index a14fafc583d4..7a4f52987a7d 100644
--- a/drivers/char/ipmi/ssif_bmc.c
+++ b/drivers/char/ipmi/ssif_bmc.c
@@ -579,7 +579,6 @@ static void process_request_part(struct ssif_bmc_ctx *ssif_bmc)
 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);
 
@@ -596,6 +595,7 @@ static void process_smbus_cmd(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
 		if (ssif_bmc->aborting)
 			ssif_bmc->aborting = false;
 	}
+	ssif_bmc->part_buf.smbus_cmd = *val;
 }
 
 static void on_read_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
-- 
2.34.1

On 01/01/2025 23:54, Cosmo Chou wrote:
> Move smbus_cmd assignment to the end of process_smbus_cmd() to ensure
> the new command is not lost when complete_response() is triggered.
> 

Thanks Cosmo for the catch.

And, IMHO, the root cause is the memset() on part buffer called in 
complete_response() is not quite correct. In the current implementation, 
the complete_response() should only be called when the READ is 
completed, ie: only on I2C_SLAVE_STOP of READ transaction, otherwise all 
the info of current on-going request will be mistakenly cleared as in 
this case.

This patch is good and I wonder if we can make this a bit further as below?

diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
index a14fafc583d4..310f17dd9511 100644
--- a/drivers/char/ipmi/ssif_bmc.c
+++ b/drivers/char/ipmi/ssif_bmc.c
@@ -292,7 +292,6 @@ static void complete_response(struct ssif_bmc_ctx 
*ssif_bmc)
         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);
  }

@@ -744,9 +743,11 @@ static void on_stop_event(struct ssif_bmc_ctx 
*ssif_bmc, u8 *val)
                         ssif_bmc->aborting = true;
                 }
         } else if (ssif_bmc->state == SSIF_RES_SENDING) {
-               if (ssif_bmc->is_singlepart_read || ssif_bmc->block_num 
== 0xFF)
+               if (ssif_bmc->is_singlepart_read || ssif_bmc->block_num 
== 0xFF) {
+                       memset(&ssif_bmc->part_buf, 0, sizeof(struct 
ssif_part_buffer));
                         /* Invalidate response buffer to denote it is 
sent */
                         complete_response(ssif_bmc);
+               }
                 ssif_bmc->state = SSIF_READY;
         }

Thanks and Happy New Year.
- Quan

On Fri, Jan 03, 2025 at 10:44:46AM +0700, Quan Nguyen wrote:
> 
> 
> On 01/01/2025 23:54, Cosmo Chou wrote:
> > Move smbus_cmd assignment to the end of process_smbus_cmd() to ensure
> > the new command is not lost when complete_response() is triggered.
> > 
> 
> Thanks Cosmo for the catch.
> 
> And, IMHO, the root cause is the memset() on part buffer called in
> complete_response() is not quite correct. In the current implementation, the
> complete_response() should only be called when the READ is completed, ie:
> only on I2C_SLAVE_STOP of READ transaction, otherwise all the info of
> current on-going request will be mistakenly cleared as in this case.
> 
> This patch is good and I wonder if we can make this a bit further as below?

Yes, this is probably more future proof.

Can you send me a formal patch, with a "Found-by:" for Cosmo?  I'll
replace Cosmo's patch.

Thanks,

-corey

> 
> diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
> index a14fafc583d4..310f17dd9511 100644
> --- a/drivers/char/ipmi/ssif_bmc.c
> +++ b/drivers/char/ipmi/ssif_bmc.c
> @@ -292,7 +292,6 @@ static void complete_response(struct ssif_bmc_ctx
> *ssif_bmc)
>         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);
>  }
> 
> @@ -744,9 +743,11 @@ static void on_stop_event(struct ssif_bmc_ctx
> *ssif_bmc, u8 *val)
>                         ssif_bmc->aborting = true;
>                 }
>         } else if (ssif_bmc->state == SSIF_RES_SENDING) {
> -               if (ssif_bmc->is_singlepart_read || ssif_bmc->block_num ==
> 0xFF)
> +               if (ssif_bmc->is_singlepart_read || ssif_bmc->block_num ==
> 0xFF) {
> +                       memset(&ssif_bmc->part_buf, 0, sizeof(struct
> ssif_part_buffer));
>                         /* Invalidate response buffer to denote it is sent
> */
>                         complete_response(ssif_bmc);
> +               }
>                 ssif_bmc->state = SSIF_READY;
>         }
> 
> Thanks and Happy New Year.
> - Quan

On 03/01/2025 20:01, Corey Minyard wrote:
> On Fri, Jan 03, 2025 at 10:44:46AM +0700, Quan Nguyen wrote:
>>
>>
>> On 01/01/2025 23:54, Cosmo Chou wrote:
>>> Move smbus_cmd assignment to the end of process_smbus_cmd() to ensure
>>> the new command is not lost when complete_response() is triggered.
>>>
>>
>> Thanks Cosmo for the catch.
>>
>> And, IMHO, the root cause is the memset() on part buffer called in
>> complete_response() is not quite correct. In the current implementation, the
>> complete_response() should only be called when the READ is completed, ie:
>> only on I2C_SLAVE_STOP of READ transaction, otherwise all the info of
>> current on-going request will be mistakenly cleared as in this case.
>>
>> This patch is good and I wonder if we can make this a bit further as below?
> 
> Yes, this is probably more future proof.
> 
> Can you send me a formal patch, with a "Found-by:" for Cosmo?  I'll
> replace Cosmo's patch.
> 

Thanks Corey,

Will send the formal patch later.

Thanks,
-- Quan

On Thu, Jan 02, 2025 at 12:54:31AM +0800, Cosmo Chou wrote:
> Move smbus_cmd assignment to the end of process_smbus_cmd() to ensure
> the new command is not lost when complete_response() is triggered.

Ok, I see, patch is applied.  Thank you.

Quan, I assume this is ok.  Please double-check it for me.

-corey

> 
> Fixes: dd2bc5cc9e25 ("ipmi: ssif_bmc: Add SSIF BMC driver")
> Signed-off-by: Cosmo Chou <chou.cosmo@gmail.com>
> ---
>  drivers/char/ipmi/ssif_bmc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/char/ipmi/ssif_bmc.c b/drivers/char/ipmi/ssif_bmc.c
> index a14fafc583d4..7a4f52987a7d 100644
> --- a/drivers/char/ipmi/ssif_bmc.c
> +++ b/drivers/char/ipmi/ssif_bmc.c
> @@ -579,7 +579,6 @@ static void process_request_part(struct ssif_bmc_ctx *ssif_bmc)
>  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);
>  
> @@ -596,6 +595,7 @@ static void process_smbus_cmd(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
>  		if (ssif_bmc->aborting)
>  			ssif_bmc->aborting = false;
>  	}
> +	ssif_bmc->part_buf.smbus_cmd = *val;
>  }
>  
>  static void on_read_requested_event(struct ssif_bmc_ctx *ssif_bmc, u8 *val)
> -- 
> 2.34.1
>

On 03/01/2025 10:20, Corey Minyard wrote:
> On Thu, Jan 02, 2025 at 12:54:31AM +0800, Cosmo Chou wrote:
>> Move smbus_cmd assignment to the end of process_smbus_cmd() to ensure
>> the new command is not lost when complete_response() is triggered.
> 
> Ok, I see, patch is applied.  Thank you.
> 
> Quan, I assume this is ok.  Please double-check it for me.
> 

Yes, Corey,

This patch looks good to me and I think this can be improved a bit 
further in my reply for Cosmo.

- Quan