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Subject: Re: [PATCH 4/6] ibmvfc: add FC payload retrieval routines for
 versioned vfcFrames
From:   Brian King <brking@linux.vnet.ibm.com>
To:     Tyrel Datwyler <tyreld@linux.ibm.com>,
        james.bottomley@hansenpartnership.com
Cc:     martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org,
        brking@linux.ibm.com
References: <20201112010442.102589-1-tyreld@linux.ibm.com>
 <20201112010442.102589-4-tyreld@linux.ibm.com>
 <9e38f449-d2e6-6408-4fef-cfb5351393cc@linux.vnet.ibm.com>
Message-ID: <a829840c-6f39-2901-4cdc-9df1d83f3196@linux.vnet.ibm.com>
Date:   Tue, 17 Nov 2020 16:21:06 -0600
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On 11/17/20 4:14 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

Even better might be vhost->version which you'd set to 1 or 2 and then you could directly
use that to set the field in the command structures later.


-- 
Brian King
Power Linux I/O
IBM Linux Technology Center