netdev - Re: [PATCH net-next 2/2] net: phy: air_en8811h: Add the Airoha EN8811H PHY driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <f3f811f8-07cd-416c-ad30-b6db42a78b03@gmail.com>
Date: Wed, 7 Feb 2024 20:23:00 +0100
From: Eric Woudstra <ericwouds@...il.com>
To: "Russell King (Oracle)" <linux@...linux.org.uk>
Cc: "David S. Miller" <davem@...emloft.net>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Rob Herring <robh+dt@...nel.org>,
 Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
 Conor Dooley <conor+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
 Heiner Kallweit <hkallweit1@...il.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Frank Wunderlich <frank-w@...lic-files.de>,
 Daniel Golle <daniel@...rotopia.org>, Lucien Jheng
 <lucien.jheng@...oha.com>, Zhi-Jun You <hujy652@...tonmail.com>,
 netdev@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH net-next 2/2] net: phy: air_en8811h: Add the Airoha
 EN8811H PHY driver

Hi Russell,

>> Searching the driver for "air_buckpbus_reg_read", there are four
>> instances where you read-modify-write, and only one instance which is
>> just a read.
>>
>> I wonder whether it would make more sense to structure the accessors as
>>
>> 	__air_buckpbus_set_address(phydev, addr)
>> 	__air_buckpbus_read(phydev, *data)
>> 	__air_buckpbus_write(phydev, data)
>>
>> which would make implementing reg_read, reg_write and reg_modify()
>> easier, and the addition of reg_modify() means that (a) there are less
>> bus cycles (through having to set the address twice) and (b) ensures
>> that the read-modify-write can be done atomically on the bus. This
>> assumes that reading data doesn't auto-increment the address (which
>> you would need to check.)
> 
> I will see if I can change the code to:
> 
>         __air_buckpbus_set_address(phydev, addr)
>         __air_buckpbus_read(phydev, *data)
>         __air_buckpbus_write(phydev, data)
>         air_buckpbus_reg_read()
>         air_buckpbus_reg_write()
>         air_buckpbus_reg_modify()
> 
> While not changing (except if (saved_page >= 0)):
> 
>         __air_write_buf()
>         air_write_buf()
> 

I just remember, the address register for write, is a different
register from the address register for read. So we always have
to write to address registers twice.

I can still implement an atomic air_buckpbus_reg_modify() though.

Best regards,

Eric Woudstra