Message-ID: <e6518637-4e78-3935-133d-79afea67cf80@acm.org>
Date:   Wed, 1 Mar 2023 10:44:06 -0800
MIME-Version: 1.0
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.7.1
Subject: Re: [PATCH 1/2] include: uapi: scsi: Change utp_upiu_query struct
Content-Language: en-US
To:     Arthur Simchaev <Arthur.Simchaev@wdc.com>,
        "martin.petersen@oracle.com" <martin.petersen@oracle.com>
Cc:     "beanhuo@micron.com" <beanhuo@micron.com>,
        "linux-scsi@vger.kernel.org" <linux-scsi@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
References: <1677078770-30994-1-git-send-email-Arthur.Simchaev@wdc.com>
 <1677078770-30994-2-git-send-email-Arthur.Simchaev@wdc.com>
 <b1f0ed44-d707-5593-7449-8a6bd23c9902@acm.org>
 <BY5PR04MB632717453EB0D403388B4F1EEDAF9@BY5PR04MB6327.namprd04.prod.outlook.com>
 <21f73bfd-1d91-106f-d3a8-eb4674c517e6@acm.org>
 <BY5PR04MB632701F87296BEE554D3F055EDAD9@BY5PR04MB6327.namprd04.prod.outlook.com>
From:   Bart Van Assche <bvanassche@acm.org>
In-Reply-To: <BY5PR04MB632701F87296BEE554D3F055EDAD9@BY5PR04MB6327.namprd04.prod.outlook.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 3/1/23 01:46, Arthur Simchaev wrote:
>>>>>    struct utp_upiu_query {
>>>>>      __u8 opcode;
>>>>>      __u8 idn;
>>>>>      __u8 index;
>>>>>      __u8 selector;
>>>>> -   __be16 reserved_osf;
>>>>> -   __be16 length;
>>>>> -   __be32 value;
>>>>> -   __be32 reserved[2];
>>>>> +   __u8 osf3;
>>>>> +   __u8 osf4;
>>>>> +   __be16 osf5;
>>>>> +   __be32 osf6;
>>>>> +   __be32 osf7;
>>>>>    };
>>>> All changes in UAPI headers must be backwards compatible. The above
>> doesn't look like a backwards compatible change to me.
>>>
>>> This API was originally invented to support ufs-bsg.
>>> AFAIK, ufs-utils is the only app that makes use of this API,
>>> and it doesn't dig into struct utp_upiu_query inner fields.
>>
>> That does not match what I see. I see that code in ufs-utils accesses
>> the 'length' and 'value' members of the above data structure.
>>
>> Please follow the rules for UAPI header files.
>>
>> Thanks,
>>
>> Bart.
> 
> You are right , my fault.
> Anyway, It just return reserved field to the struct.
> Also I can update the tool accordingly. Instead length and value fields,
> using osf5 and osf6.
> In this case we will keep it backward compatible.
> Is it OK?

Hi Arthur,

I doubt that renaming structure members is acceptable for UAPI headers. 
How about introducing a second struct next to the utp_upiu_query struct?

Thanks,

Bart.