Hi Jean, On Tue, Oct 17, 2023 at 05:06:08PM +0200, Jean Delvare wrote: > 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. thanks for clarifying! Andi > > 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
