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813c2dd786
sfp->i2c_block_size is initialized at SFP module insertion in
sfp_sm_mod_probe(). Because of that, if SFP module was never inserted
since boot, sfp_read() call will lead to zero-length I2C read attempt,
and not all I2C controllers are happy with zero-length reads.
One way to issue sfp_read() on empty SFP cage is to execute ethtool -m.
If SFP module was never plugged since boot, there will be a zero-length
I2C read attempt.
# ethtool -m xge0
i2c i2c-3: adapter quirk: no zero length (addr 0x0050, size 0, read)
Cannot get Module EEPROM data: Operation not supported
If SFP module was plugged then removed at least once,
sfp->i2c_block_size will be initialized and ethtool -m will fail with
different exit code and without I2C error
# ethtool -m xge0
Cannot get Module EEPROM data: Remote I/O error
Fix this by initializing sfp->i2_block_size at struct sfp allocation
stage so no wild sfp_read() could issue zero-length I2C read.
Signed-off-by: Ivan Bornyakov <i.bornyakov@metrotek.ru>
Fixes: 0d035bed2a ("net: sfp: VSOL V2801F / CarlitoxxPro CPGOS03-0490 v2.0 workaround")
Cc: stable@vger.kernel.org
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.