Hi Heiner, Andi, On Tue, 10 Oct 2023 21:27:44 +0200, Heiner Kallweit wrote: > Now that the legacy eeprom driver was removed, the only remaining i2c > client driver with class SPD autodetection is jc42, and this driver > supports also class HWMON. Therefore we can remove class SPD from the I did not notice this change when it happened back in 2016. This broke the i2c-i801 driver as a side effect, because the Asus-specific mux code assumes that no I2C device driver can probe both the SMBus trunk and the SMBus segments behind the muxes. This is done (as you must know as this patch touches that part of the code) by ensuring that the trunk and the muxed segments do not share any class flag. This was sufficient as long as all device driver themselves only registered for one class, but this is no longer the case of the jc42 driver. So loading the jc42 driver on one of these Asus server board systems would possibly result in multiple jc42 devices being instantiated for the same underlying hardware device. The one instantiated on the trunk would return incorrect values or errors depending on the mux setting. Probably this went unnoticed because nobody was running such old server boards when the change happened, or they would stick to older kernel versions. > supported classes of the i801 adapter driver. > Legacy class-based instantiation shouldn't be used in new code, so I > think we can remove also the generic logic that ensures that supported > classes of parent and muxed adapters don't overlap. Agreed. If we were to add support for a new server board with muxed SMBus, we would disable class-based probing and instead explicitly instantiate devices. To be honest, I don't know why we didn't do that for the Asus Z8 series already, as I think it was already available, and it would have made the code a lot more simple. If anyone ever complains about the bug mentioned above, then we'll have to do it anyway. > Note: i801 parent supports just class HWMON now, and muxed childs "children" ^^ > class SPD, so the supported classes don't overlap. > > Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx> > --- > drivers/i2c/busses/i2c-i801.c | 38 +++++++---------------------------- > 1 file changed, 7 insertions(+), 31 deletions(-) > (...) Fine with me. Reviewed-by: Jean Delvare <jdelvare@xxxxxxx> -- Jean Delvare SUSE L3 Support
