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: 0d035bed2a4a ("net: sfp: VSOL V2801F / CarlitoxxPro CPGOS03-0490 v2.0 workaround") Cc: stable@vger.kernel.org --- drivers/net/phy/sfp.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c index 40c9a64c5e30..5663a184644d 100644 --- a/drivers/net/phy/sfp.c +++ b/drivers/net/phy/sfp.c @@ -212,6 +212,12 @@ static const enum gpiod_flags gpio_flags[] = { #define SFP_PHY_ADDR 22 #define SFP_PHY_ADDR_ROLLBALL 17

+/* 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 + struct sff_data { unsigned int gpios; bool (*module_supported)(const struct sfp_eeprom_id *id); @@ -1928,11 +1934,7 @@ static int sfp_sm_mod_probe(struct sfp *sfp, bool report) u8 check; int ret;

- /* Some SFP modules and also some Linux I2C drivers do not like reads - * longer than 16 bytes, so read the EEPROM in chunks of 16 bytes at - * a time. - */ - sfp->i2c_block_size = 16; + sfp->i2c_block_size = SFP_EEPROM_BLOCK_SIZE;

ret = sfp_read(sfp, false, 0, &id.base, sizeof(id.base)); if (ret < 0) { @@ -2615,6 +2617,7 @@ static struct sfp *sfp_alloc(struct device *dev) return ERR_PTR(-ENOMEM);

sfp->dev = dev; + sfp->i2c_block_size = SFP_EEPROM_BLOCK_SIZE;

mutex_init(&sfp->sm_mutex); mutex_init(&sfp->st_mutex);