[PATCH v2 0/4] i2c: Support i2c_register_spd() on multiplexed bus segments

Heiner Kallweit
2024-01-13T11:23:57Z

i801 is the last bus driver supporting I2C_CLASS_SPD. It's used for
device probing on muxed bus segments. Only known use case so far is
systems with more than 8 memory modules (with thermal sensor) on
muxed smbus segments.
As discussed with Jean, to be able to remove I2C_CLASS_SPD completely
the following has to be done:

1. Extend i2c_register_spd() for use on muxed bus segments
2. Enable explicit instantiation of thermal sensors on memory modules
3. Extend i801 to call i2c_register_spd() on muxed bus segments

Step 2 has been accomplished:
caba40ec3531 ("eeprom: at24: Probe for DDR3 thermal sensor in the SPD case")
393bd1000f81 ("eeprom: ee1004: add support for temperature sensor")

Patch 1 does step 1
Patches 2 and 3 provide the basis for patch 4
Patch 4 does step 3

Note: i801 creates the mux platform device, loading and probing of the
mux driver may be asynchronous. Therefore we can't call i2c_register_spd()
for the muxed segments from i801. Instead we have to add a flag to the
platform data, so that the mux driver knows it's supposed to call
i2c_register_spd().

This series replaces the earlier RFC series.

v2:
- remove now obsolete comment in patch 1
- fix link error in some configs in patch 2

Heiner Kallweit (4):
i2c: smbus: Prepare i2c_register_spd for usage on muxed segments
i2c: mux: add basic support for calling i2c_register_spd on muxed bus
segments
i2c: mux: gpio: Allow to call i2c_register_spd on a muxed segment
i2c: i801: Call i2c_register_spd() on muxed bus segments

drivers/i2c/Kconfig | 1 +
drivers/i2c/busses/i2c-i801.c | 1 +
drivers/i2c/i2c-mux.c | 4 ++++
drivers/i2c/i2c-smbus.c | 20 ++++++++++++--------
drivers/i2c/muxes/i2c-mux-gpio.c | 1 +
include/linux/i2c-mux.h | 1 +
include/linux/platform_data/i2c-mux-gpio.h | 2 ++
7 files changed, 22 insertions(+), 8 deletions(-)

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2.43.0