Rudolf Marek wrote: > Hello, > > 2) Some kind of multiplexing bus driver that will allow us to "see" both of > memory EEPROMs and monitoring chip. > > Ad 2) > Thank you for information there are very helpful. We agreed with Jean that most > clean solution to a problem would be a "multiplexing bus driver" (users can use > until this is done the isaset trick). As you might noticed the multiplexer just > switches the intel SMBus host between four busses. We are interrested in bus 0 > and bus 1. One is with SPD EEPROMs and second contain 792 chip. We have already > similar driver in kernel for this that is called i2c-amd756-s4882.c. > > Your driver will be very similar except that the multiplexer itself is not > on the smbus but you need to do same trick as with isaset command. Generally > you would need to register the PCI device to your multiplexing driver, get the > GPIO base addr (same as my hide and seek patch) and switch it to 0x0 or 0x08 > when you have request from bus 0 or bus 1... > > How is the multiplexed bus concept working: > > It creates more busses from i2c core point of view. When there is some request > to read or write from a driver it will go to this virtual bus driver, > this driver will switch the bus and call the original driver. So it just create > handlers for "xfer" function that is the transmission function. > > When it is done you will have more virtual busses. > > modprobe i2c-i801 > modprobe your multiplex driver > > so if you will do > i2cdetect 0 > It will switch the multiplexer and you will see only SPD eeproms here > if you will do: > i2cdetect 1 > You will see addresses with 792 chip. > > Later you just modprobe eeprom and modprobe w83792 and all will work as expected > . You will see in sensors command both eeproms and chip data. > > The existing driver has 200 lines and I guess yours would have like 300 so it is > not so difficult to write it. Unfortunalely I'm quite busy these days and Jean > has a lot of work too so I cant write it for you but of course I will help you. > This is a good time to bring up the i2c-virtual driver as an alternative to the -s4882.c style of multiplexing driver. I believe this is a cleaner and more general approach to bus multiplexing. The i2c-virtual driver is checked in to sensors but the small changes required to i2c-core.c are not checked in. I held off late last year because 2.9.0 was coming out soon. Now that 2.9.1 is out it's time to look at it again. I have to rework the i2c-core changes because they conflicted with other recent changes to i2c-core. attached are the proposed changes to i2c-core for comment. mds -------------- next part -------------- An embedded and charset-unspecified text was scrubbed... Name: i2c-core.diff Url: http://lists.lm-sensors.org/pipermail/lm-sensors/attachments/20050418/ba23a5a0/attachment.pl
