netdev - Re: [PATCH V7 8/9] PCI/IOV: Add 10-Bit Tag sysfs files for VF devices

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Date:   Thu, 5 Aug 2021 17:39:35 +0800
From:   Dongdong Liu <liudongdong3@...wei.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
CC:     <hch@...radead.org>, <kw@...ux.com>, <logang@...tatee.com>,
        <leon@...nel.org>, <linux-pci@...r.kernel.org>,
        <rajur@...lsio.com>, <hverkuil-cisco@...all.nl>,
        <linux-media@...r.kernel.org>, <netdev@...r.kernel.org>
Subject: Re: [PATCH V7 8/9] PCI/IOV: Add 10-Bit Tag sysfs files for VF devices

Miss a comment reply  :).

On 2021/8/5 8:05, Bjorn Helgaas wrote:
> On Wed, Aug 04, 2021 at 09:47:07PM +0800, Dongdong Liu wrote:
>> PCIe spec 5.0 r1.0 section 2.2.6.2 says that if an Endpoint supports
>> sending Requests to other Endpoints (as opposed to host memory), the
>> Endpoint must not send 10-Bit Tag Requests to another given Endpoint
>> unless an implementation-specific mechanism determines that the
>> Endpoint supports 10-Bit Tag Completer capability.
>> Add sriov_vf_10bit_tag file to query the status of VF 10-Bit Tag
>> Requester Enable. Add sriov_vf_10bit_tag_ctl file to disable the VF
>> 10-Bit Tag Requester. The typical use case is for p2pdma when the peer
>> device does not support 10-BIT Tag Completer.
>
> Fix the usual spec quoting issue.  Or maybe this is not actually
> quoted but is missing blank lines between paragraphs.
>
> s/10-BIT/10-Bit/
>
>> Signed-off-by: Dongdong Liu <liudongdong3@...wei.com>
>> ---
>>  Documentation/ABI/testing/sysfs-bus-pci | 20 +++++++++++++
>>  drivers/pci/iov.c                       | 50 +++++++++++++++++++++++++++++++++
>>  2 files changed, 70 insertions(+)
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
>> index 0e0c97d..8fdbfae 100644
>> --- a/Documentation/ABI/testing/sysfs-bus-pci
>> +++ b/Documentation/ABI/testing/sysfs-bus-pci
>> @@ -421,3 +421,23 @@ Description:
>>  		to disable 10-Bit Tag Requester when the driver does not bind
>>  		the deivce. The typical use case is for p2pdma when the peer
>>  		device does not support 10-BIT Tag Completer.
>> +
>> +What:		/sys/bus/pci/devices/.../sriov_vf_10bit_tag
>> +Date:		August 2021
>> +Contact:	Dongdong Liu <liudongdong3@...wei.com>
>> +Description:
>> +		This file is associated with a SR-IOV physical function (PF).
>> +		It is visible when the device has VF 10-Bit Tag Requester
>> +		Supported. It contains the status of VF 10-Bit Tag Requester
>> +		Enable. The file is only readable.
>
> s/only readable/read-only/
>
>> +What:		/sys/bus/pci/devices/.../sriov_vf_10bit_tag_ctl
>
> Why does this file have "_ctl" on the end when the one in patch 7/9
> does not?

PF: 0000:82:00.0  VF:0000:82:10.0
/sys/bus/pci/devices/0000:82:00.0/sriov_vf_10bit_tag
/sys/bus/pci/devices/0000:82:10.0/sriov_vf_10bit_tag_ctl

sriov_vf_10bit_tag is used to qeury the status of VF 10-Bit Tag
Requester Enable,  bind with PF device.

sriov_vf_10bit_tag_ctl is used to disable the VF 10-Bit Tag Requester,
bind with VF device, although in fact it writes PF SR-IOV control 
register, just detect if the VF driver have already bond with the VF deivce.

Thanks,
Dongdong