Re: [PATCH v3 15/16] HID: ft260: i2c: recover a bus held by a slave

[sashiko-bot@kernel.org]

> An SMBus block read takes the first byte the slave sends as the block
> length. An EEPROM has no length byte, it answers with stored data, and
> ft260_smbus_xfer() rejects a value above I2C_SMBUS_BLOCK_MAX. That
> count phase carries no STOP, so the slave keeps SDA low while it waits
> for the next clock. FT260_SET_I2C_RESET restarts the controller but
> does not clock the bus, the chip cannot put a STOP on the line, and
> every later START ends in arbitration lost.
> 
> A 24c02 holds 0x68 at offset 0x80, so on that bus
> 
>   i2cget -y 0 0x50 0x80 s
>   ft260 0003:0403:6030.0011: smbus block read: invalid count 104 from slave 0x50
> 
> killed the bus: every transfer after it failed with bus_status 0x72
> (bus busy, controller idle, arbitration lost, error). The sysfs
> [ ... ]
> recovery: a full i2cdetect scan of 112 addresses logs no "recovering"
> line.
> 
> Fixes: 2d68d67151eb ("HID: ft260: fix SMBus block read protocol handling")
> Signed-off-by: Michael Zaidman <michael.zaidman@gmail.com>

Sashiko has reviewed this patch and found no issues.

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Sashiko AI review · https://sashiko.dev/#/patchset/20261114230800.1344401-1-michael.zaidman@gmail.com?part=15