netdev - Re: [PATCH net-next 1/2] net: ethtool: Add new parameters and a function to support EPL

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 for Android: free password hash cracker in your pocket

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

Message-ID: <970ef9b1-609b-4137-a76f-315c99fbf112@lunn.ch>
Date: Fri, 6 Sep 2024 17:36:06 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Danielle Ratson <danieller@...dia.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
	kuba@...nel.org, pabeni@...hat.com, yuehaibing@...wei.com,
	linux-kernel@...r.kernel.org, petrm@...dia.com
Subject: Re: [PATCH net-next 1/2] net: ethtool: Add new parameters and a
 function to support EPL

> +/* For accessing the EPL field on page 9Fh, the allowable length extension is
> + * min(i, 255) byte octets where i specifies the allowable additional number of
> + * byte octets in a READ or a WRITE.
> + */
> +u32 ethtool_cmis_get_max_epl_size(u8 num_of_byte_octs)
> +{
> +	return 8 * (1 + min_t(u8, num_of_byte_octs, 255));
> +}

Does this get mapped to a 255 byte I2C bus transfer?

https://elixir.bootlin.com/linux/v6.11-rc6/source/drivers/net/phy/sfp.c#L218

/* SFP_EEPROM_BLOCK_SIZE is the size of data chunk to read the EEPROM
 * at a time. Some SFP modules and also some Linux I2C drivers do not like
 * reads longer than 16 bytes.
 */
#define SFP_EEPROM_BLOCK_SIZE	16

If an SMBUS is being used, rather than I2C, there is a hard limit of
32 bytes in a message transfer.

I've not looked in details at these patches, but maybe you need a
mechanism to ask the hardware or I2C driver what it can actually do?
Is it possible to say LPL is the only choice?

	Andrew