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Date: Thu, 7 Mar 2024 11:17:08 +0000
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v7 5/7] scsi: hisi_sas: Add libsas SATA sysfs attributes
 group
To: Niklas Cassel <cassel@kernel.org>
Cc: Igor Pylypiv <ipylypiv@google.com>, Damien Le Moal <dlemoal@kernel.org>,
        Jason Yan <yanaijie@huawei.com>,
        "James E.J. Bottomley"
 <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Jack Wang <jinpu.wang@cloud.ionos.com>, Hannes Reinecke <hare@suse.de>,
        Xiang Chen <chenxiang66@hisilicon.com>,
        Artur Paszkiewicz <artur.paszkiewicz@intel.com>,
        Bart Van Assche <bvanassche@acm.org>, TJ Adams <tadamsjr@google.com>,
        linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20240306012226.3398927-1-ipylypiv@google.com>
 <20240306012226.3398927-6-ipylypiv@google.com> <ZehLpV06mpHxjecc@ryzen>
 <ZejYb4ykeF7Qx5a5@google.com>
 <c3ebaa55-d05b-4f11-83a8-2a0fb85044cf@oracle.com> <ZemQBLMcJP617WDC@ryzen>
Content-Language: en-US
From: John Garry <john.g.garry@oracle.com>
Organization: Oracle Corporation
In-Reply-To: <ZemQBLMcJP617WDC@ryzen>
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> John, now I'm curious, do you know why hisi_sas_v1_hw.c is implemented
> as a libsas driver (instead of a regular SCSI driver), if it doesn't
> support SATA?

Using libsas is not really dependent on whether the HW supports SATA/STP 
or not. It's a protocol layer thing. Considering the SAS protocol stack, 
HW for drivers using libsas have implemented only the lower protocol 
layers, and SW, i.e. libsas, is required to manage upper layers, like 
Port layer and above.

BTW, IIRC, v1 hw did support SATA, but not STP, i.e. directly attached 
SATA only, but the SATA support was even more broken than v2 hw (which 
is quite broken), so never bothered supporting in SW.

> 
> Was perhaps v2_hw and v3_hw implemented as a libsas driver first
> (since they support SATA), and v1_hw support was added later,
> so that it could reuse much of the parts of the existing driver?

v1 driver support came first.

Thanks,
John