net: sfp: apply I2C adapter quirks to limit block size

The SFP driver assumes all I2C adapters support reading and writing the
pre-defined block size SFP_EEPROM_BLOCK_SIZE of 16 bytes. This constant
was probably chosen based on good guesses and known limitations of a
range of I2C adapters and SFP modules.

However, I2C adapters may even support less and usually need to specify
this via I2C quirks. Theoretically, such an adapter may provide full
functionality but only support a read and write length of e.g. 8 bytes.
Currently, the SFP driver doesn't account for that.

Add handling for I2C quirks in SFP I2C configuration taking the fields
max_read_len and max_write_len in struct i2c_adapter_quirks into account
to further limit the maximum block size if needed.

Signed-off-by: Jonas Jelonek <jelonek.jonas@gmail.com>
Reviewed-by: Maxime Chevallier <maxime.chevallier@bootlin.com>
Link: https://patch.msgid.link/20260614133418.2068201-2-jelonek.jonas@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/drivers/net/phy/sfp.c b/drivers/net/phy/sfp.c
index caeda3291b301c6c8084dcc5b11b622e41d0ffc7..9b6552632b27b010d920a815225217690e87cea6 100644 (file)
--- a/drivers/net/phy/sfp.c
+++ b/drivers/net/phy/sfp.c
@@ -827,21 +827,29 @@ static int sfp_smbus_byte_write(struct sfp *sfp, bool a2, u8 dev_addr,
 
 static int sfp_i2c_configure(struct sfp *sfp, struct i2c_adapter *i2c)
 {
+       size_t max_block_size;
+
        sfp->i2c = i2c;
 
        if (i2c_check_functionality(i2c, I2C_FUNC_I2C)) {
                sfp->read = sfp_i2c_read;
                sfp->write = sfp_i2c_write;
-               sfp->i2c_max_block_size = SFP_EEPROM_BLOCK_SIZE;
+               max_block_size = SFP_EEPROM_BLOCK_SIZE;
        } else if (i2c_check_functionality(i2c, I2C_FUNC_SMBUS_BYTE_DATA)) {
                sfp->read = sfp_smbus_byte_read;
                sfp->write = sfp_smbus_byte_write;
-               sfp->i2c_max_block_size = 1;
+               max_block_size = 1;
        } else {
                sfp->i2c = NULL;
                return -EINVAL;
        }
 
+       if (i2c->quirks && i2c->quirks->max_read_len)
+               max_block_size = min(max_block_size, i2c->quirks->max_read_len);
+       if (i2c->quirks && i2c->quirks->max_write_len)
+               max_block_size = min(max_block_size, i2c->quirks->max_write_len);
+
+       sfp->i2c_max_block_size = max_block_size;
        sfp->i2c_block_size = sfp->i2c_max_block_size;
        return 0;
 }