From: Andrew Lunn <andrew@lunn•ch>
To: Moshe Shemesh <moshe@nvidia•com>
Cc: "David S. Miller" <davem@davemloft•net>,
Jakub Kicinski <kuba@kernel•org>,
Adrian Pop <pop.adrian61@gmail•com>,
Michal Kubecek <mkubecek@suse•cz>,
Don Bollinger <don@thebollingers•org>,
netdev@vger•kernel.org,
Vladyslav Tarasiuk <vladyslavt@nvidia•com>
Subject: Re: [RFC PATCH V3 net-next 1/5] ethtool: Allow network drivers to dump arbitrary EEPROM data
Date: Thu, 18 Mar 2021 23:16:16 +0100 [thread overview]
Message-ID: <YFPRMEa/CfZKsMyA@lunn.ch> (raw)
In-Reply-To: <3d8b9b2b-25e2-3812-2daf-09f1c5088eb0@nvidia.com>
> > > +Request contents:
> > > +
> > > + ===================================== ====== ==========================
> > > + ``ETHTOOL_A_EEPROM_DATA_HEADER`` nested request header
> > > + ``ETHTOOL_A_EEPROM_DATA_OFFSET`` u32 offset within a page
> > > + ``ETHTOOL_A_EEPROM_DATA_LENGTH`` u32 amount of bytes to read
> > I wonder if offset and length should be u8. At most, we should only be
> > returning a 1/2 page, so 128 bytes. We don't need a u32.
>
>
> That's right when page is given, but user may have commands that
> used to work on the ioctl KAPI with offset higher than one page.
CMIS section 5.4.1 says:
The slave maintains an internal current byte address counter
containing the byte address accessed during the latest read or write
operation incremented by one with roll-over as follows: The current
byte address counter rolls-over after a read or write operation at
the last byte address of the current 128-byte memory page (127 or
255) to the first byte address (0 or 128) of the same 128-byte
memory page.
This wrapping is somewhat unexpected. If the user access is for a read
starting at 120 and a length of 20, they get bytes 120-127 followed by
0-11. The user is more likely to be expecting 120-139.
We have two ways to address this:
1) We limit reads to a maximum of a 1/2 page, and the start and end
point needs to be within that 1/2 page.
2) We detect that the read is going to go across a 1/2 page boarder,
and perform two reads to the MAC driver, and glue the data back
together again in the ethtool core.
What i don't want is to leave the individual drivers to solve this,
because i expect some of them will get it wrong.
Andrew
next prev parent reply other threads:[~2021-03-18 22:17 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-15 17:12 [RFC PATCH V3 net-next 0/5] ethtool: Extend module EEPROM dump API Moshe Shemesh
2021-03-15 17:12 ` [RFC PATCH V3 net-next 1/5] ethtool: Allow network drivers to dump arbitrary EEPROM data Moshe Shemesh
2021-03-15 21:01 ` Jakub Kicinski
2021-03-16 17:59 ` Moshe Shemesh
2021-03-15 22:31 ` Don Bollinger
2021-03-16 18:23 ` Moshe Shemesh
2021-03-16 21:00 ` Don Bollinger
2021-03-18 22:36 ` Andrew Lunn
2021-03-18 13:03 ` Andrew Lunn
2021-03-18 14:25 ` Moshe Shemesh
2021-03-18 22:16 ` Andrew Lunn [this message]
2021-03-18 15:16 ` Michal Kubecek
2021-03-15 17:12 ` [RFC PATCH V3 net-next 2/5] net/mlx5: Refactor module EEPROM query Moshe Shemesh
2021-03-15 17:12 ` [RFC PATCH V3 net-next 3/5] net/mlx5: Implement get_module_eeprom_data_by_page() Moshe Shemesh
2021-03-15 17:12 ` [RFC PATCH V3 net-next 4/5] net/mlx5: Add support for DSFP module EEPROM dumps Moshe Shemesh
2021-03-15 17:12 ` [RFC PATCH V3 net-next 5/5] ethtool: Add fallback to get_module_eeprom from netlink command Moshe Shemesh
2021-03-15 22:31 ` Don Bollinger
2021-03-16 18:26 ` Moshe Shemesh
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