Am 13.02.2013 16:36, schrieb Gerlando Falauto: > Hi everyone, > > On 07/09/2010 11:07 AM, Michael Lawnick wrote: >> Add multiplexed bus core support. I2C multiplexer and switches >> like pca954x get instantiated as new adapters per port. >> >> Signed-off-by: Michael Lawnick<demx1175@wbit01lx.(none)> >> Cc: Jean Delvare<khali-PUYAD+kWke1g9hUCZPvPmw@xxxxxxxxxxxxxxxx> > > 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) ... > 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... > > So I guess the easiest thing to do would be to add this information > within the .name attribute, though I fear this may somehow turn out not > as trivial at it looks. Jean already detected this problem when mux code was brought into kernel, but solution was postponed until someone gets enough pain ;-) On my project I do no automatic i2c detection, but all is controlled via user space. So I always know where and which devices and buses get connected. > > devices/platform/i2c-gpio/i2c-0/0-0070/chan-4(=>...i2c-5)/5-0071/chan-0(=>...i2c-9) > devices/platform/i2c-gpio/i2c-0/0-0070/chan-4(=>...i2c-5)/5-0071/chan-1(=>...i2c-10) > devices/platform/i2c-gpio/i2c-0/0-0070/chan-4(=>...i2c-5)/5-0071/chan-2(=>...i2c-11) > devices/platform/i2c-gpio/i2c-0/0-0070/chan-4(=>...i2c-5)/5-0071/chan-3(=>...i2c-12) Introducing links to sub-buses, named with respective channel id sounds good for me. Beside that your link example does not reflect your ASCII graphics of course ;-) -- KR Michael -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
