linux-kernel - Re: [PATCH net-next 1/2] net: phy: phy-c45: add SQI and SQI+ support for OATC14 10Base-T1S PHYs

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Message-ID: <7c0e51cf-df0b-4be1-851b-c91ea45f3380@microchip.com>
Date: Mon, 17 Nov 2025 05:43:01 +0000
From: <Parthiban.Veerasooran@...rochip.com>
To: <andrew@...n.ch>
CC: <piergiorgio.beruto@...il.com>, <hkallweit1@...il.com>,
	<linux@...linux.org.uk>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net-next 1/2] net: phy: phy-c45: add SQI and SQI+ support
 for OATC14 10Base-T1S PHYs

Hi Andrew,

On 14/11/25 8:02 pm, Andrew Lunn wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you know the content is safe
> 
>> If I understand correctly, do you mean to store the capability details
>> in the phydev structure when genphy_c45_oatc14_get_sqi_max() is called,
>> and then use them in the genphy_c45_oatc14_get_sqi() function?
>>
>> In that case, I may need to introduce new parameters in the phydev
>> structure. Do you think introducing new parameters in the phydev
>> structure is still necessary for this?
> 
> I'm not sure it is worth it. Do we expect an SNMP agent polling the
> SQI value once per second? Once per minute? One extra read per minute
> costs nothing. If it was happening more frequently, then it might be
> worth caching the capabilities.
> 
> How do you see this being used?

Good point — thanks for pointing it out.

Currently, ethtool reads the SQI value and displays it as part of the 
statistics. It looks like the current SNMP agent implementation isn’t 
polling the SQI value. However, it is possible that some vendors may 
implement this in their networks, in which case we might run into the 
issue of reading SQI capabilities multiple times.

To be on the safe side, and per your suggestion, I will cache/store the 
SQI capability details in the PHY device structure in the next version.

Best regards,
Parthiban V
> 
>          Andrew