Hi everyone,
I noticed that when you have multiple muxes connected to the same branch,
implementation hides some information about the complete i2c topology.
So for instance if I have something like (notice there are three PCA9544's "in
parallel", each with its own address, which I assume is a bit unusual):
# CPU (i2c-0)
# '--I2C Mux0 (PCA9547) @ 0x70
# +--Port0 (i2c-1)
# +--Port1 (i2c-2)
# +--Port2 (i2c-3)
# +--Port3 (i2c-4)
# +--Port4 (i2c-5)
# | '--- I2C Mux1 (PCA9544) @ 0x74
# | | +--Port0 (i2c-9)
# | | +--Port1 (i2c-10)
# | | +--Port2 (i2c-11)
# | | '--Port3 (i2c-12)
# | +--- I2C Mux2 (PCA9544) @ 0x71
# | | +--Port0 (i2c-13)
# | | +--Port1 (i2c-14)
# | | +--Port2 (i2c-15)
# | | '--Port3 (i2c-16)
# | '--- I2C Mux3 (PCA9544) @ 0x72
# | +--Port0 (i2c-17)
# | +--Port1 (i2c-18)
# | +--Port2 (i2c-19)
# | '--Port3 (i2c-20)
# +--Port5 (i2c-6)
# +--Port6 (i2c-7)
# '--Port7 (i2c-8)
under /sys/bus/i2c/devices/ I get:
0-0010 -> ../../../devices/platform/i2c-gpio/i2c-0/0-0010
0-0011 -> ../../../devices/platform/i2c-gpio/i2c-0/0-0011
0-0070 -> ../../../devices/platform/i2c-gpio/i2c-0/0-0070
5-0071 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/5-0071
5-0072 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/5-0072
5-0074 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/5-0074
|2c-0 -> ../../../devices/platform/i2c-gpio/i2c-0
i2c-1 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-1
i2c-2 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-2
i2c-3 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-3
i2c-4 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-4
i2c-5 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5
i2c-6 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-6
i2c-7 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-7
i2c-8 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-8
i2c-9 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-9
i2c-10 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-10
i2c-11 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-11
i2c-12 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-12
i2c-13 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-13
i2c-14 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-14
i2c-15 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-15
i2c-16 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-16
i2c-17 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-17
i2c-18 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-18
i2c-19 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-19
i2c-20 -> ../../../devices/platform/i2c-gpio/i2c-0/i2c-5/i2c-20
So I have no way of telling that:
i2c-{9,10,11,12} are connected to mux1 at address 0x74 of i2c-5
i2c-{13,14,15,16} are connected to mux2 at address 0x71 of i2c-5
i2c-{17,18,19,20} are connected to mux3 at address 0x72 of i2c-5
because I get:
# cat /sys/bus/i2c/devices/i2c-9/name
i2c-5-mux (chan_id 0)
# cat /sys/bus/i2c/devices/i2c-13/name
i2c-5-mux (chan_id 0)
which only reveals i2c-9 is the bus segment connected to channel 0 of a mux
behind i2c-5, but since there's two of them, I have no way to tell which one...
The first patch moves i2c-{n} devices under the mux device, so instead of:
/sys/class/i2c-dev/i2c-0/device/i2c-5/i2c-9
/sys/class/i2c-dev/i2c-0/device/i2c-5/i2c-10
/sys/class/i2c-dev/i2c-0/device/i2c-5/i2c-11
/sys/class/i2c-dev/i2c-0/device/i2c-5/i2c-12
you get:
/sys/class/i2c-dev/i2c-0/device/0-0070/i2c-5/5-0071/i2c-9
/sys/class/i2c-dev/i2c-0/device/0-0070/i2c-5/5-0071/i2c-10
/sys/class/i2c-dev/i2c-0/device/0-0070/i2c-5/5-0071/i2c-11
/sys/class/i2c-dev/i2c-0/device/0-0070/i2c-5/5-0071/i2c-12
The second one creates symlinks like:
/sys/class/i2c-dev/i2c-0/device/0-0070/channel-4 -> i2c-5
/sys/class/i2c-dev/i2c-0/device/0-0070/channel-4/5-0074/channel-0 -> i2c-9
/sys/class/i2c-dev/i2c-0/device/0-0070/channel-4/5-0074/channel-1 -> i2c-10
/sys/class/i2c-dev/i2c-0/device/0-0070/channel-4/5-0074/channel-3 -> i2c-11
/sys/class/i2c-dev/i2c-0/device/0-0070/channel-4/5-0074/channel-3 -> i2c-12
Gerlando Falauto (2):
i2c-mux: create mux busses under a different parent device
i2c-mux: create "channel-n" symlinks for child segments
drivers/i2c/i2c-mux.c | 20 +++++++++++++++++++-
drivers/i2c/muxes/gpio-i2cmux.c | 2 +-
drivers/i2c/muxes/pca9541.c | 2 +-
drivers/i2c/muxes/pca954x.c | 2 +-
include/linux/i2c-mux.h | 1 +
5 files changed, 23 insertions(+), 4 deletions(-)
--
1.7.10.1
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