Re: [PATCH 4/6] ibmvfc: add FC payload retrieval routines for versioned vfcFrames

[Tyrel Datwyler <tyreld@linux.ibm.com>]

On 11/17/20 2:14 PM, Brian King wrote:
> On 11/11/20 7:04 PM, Tyrel Datwyler wrote:
>> The FC iu and response payloads are located at different offsets
>> depending on the ibmvfc_cmd version. This is a result of the version 2
>> vfcFrame definition adding an extra 64bytes of reserved space to the
>> structure prior to the payloads.
>>
>> Add helper routines to determine the current vfcFrame version and
>> returning pointers to the proper iu or response structures within that
>> ibmvfc_cmd.
>>
>> Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
>> ---
>>  drivers/scsi/ibmvscsi/ibmvfc.c | 76 ++++++++++++++++++++++++----------
>>  1 file changed, 53 insertions(+), 23 deletions(-)
>>
>> diff --git a/drivers/scsi/ibmvscsi/ibmvfc.c b/drivers/scsi/ibmvscsi/ibmvfc.c
>> index aa3445bec42c..5e666f7c9266 100644
>> --- a/drivers/scsi/ibmvscsi/ibmvfc.c
>> +++ b/drivers/scsi/ibmvscsi/ibmvfc.c
>> @@ -138,6 +138,22 @@ static void ibmvfc_tgt_move_login(struct ibmvfc_target *);
>>  
>>  static const char *unknown_error = "unknown error";
>>  
>> +static struct ibmvfc_fcp_cmd_iu *ibmvfc_get_fcp_iu(struct ibmvfc_host *vhost, struct ibmvfc_cmd *vfc_cmd)
>> +{
>> +	if (be64_to_cpu(vhost->login_buf->resp.capabilities) & IBMVFC_HANDLE_VF_WWPN)
> 
> Suggest adding a flag to the vhost structure that you setup after login in order to
> simplify this check and avoid chasing multiple pointers along with a byte swap.
> 
> Maybe something like:
> 
> vhost->is_v2

I considered that, but opted instead in my v2 respin to add a helper routine to
test login response capabilities since we will also need to check for VIOS
channel support.

-Tyrel

> 
>> +		return &vfc_cmd->v2.iu;
>> +	else
>> +		return &vfc_cmd->v1.iu;
>> +}
>> +
>> +static struct ibmvfc_fcp_rsp *ibmvfc_get_fcp_rsp(struct ibmvfc_host *vhost, struct ibmvfc_cmd *vfc_cmd)
>> +{
>> +	if (be64_to_cpu(vhost->login_buf->resp.capabilities) & IBMVFC_HANDLE_VF_WWPN)
> 
> Same here
> 
>> +		return &vfc_cmd->v2.rsp;
>> +	else
>> +		return &vfc_cmd->v1.rsp;
>> +}
>> +
>>  #ifdef CONFIG_SCSI_IBMVFC_TRACE
>>  /**
>>   * ibmvfc_trc_start - Log a start trace entry
> 
> 
>