[linux-dvb] bus control

Patrick Boettcher patrick.boettcher at desy.de
Wed Jul 25 19:34:09 CEST 2007


On Mon, 23 Jul 2007, Oliver Endriss wrote:

> Manu Abraham wrote:
> > Hi all,
> > 
> > On one of the devices that i am working upon, it has a bus control entity. ie
> > 
> > The device looks like this
> > 
> > The device consists of
> > 
> > 1) a BUS Interface Unit
> > 2) on this bus Interface unit (BIU) there is one single physical I2C bus
> > 3) a built in MASTER demodulator
> > 
> > 
> > The I2C bus on the device is _not_ directly connected to any
> > peripherals such as demods and or tuners.
> > 
> > The bus goes to a control unit where the bus is split into 2 based on
> > a control word sent to the  Bus Control Unit (BCU)
> > 
> > The split out bus goes out like this
> > 
> > 1) goes to the MASTER tuner for the built in demodulator
> > 2) goes to a SLAVE demodulator, which has just one switchable I2C
> > output for the tuner
> > 
> > ie , the configuration looks like 2, 2 way switches cascaded together,
> > when the MASTER and SLAVE demodulators are cascaded.
> > 
> > Looking at the device and thinking a lot, i don't see how the control
> > can fit in as a part of the frontend at all, as the it has nothing to
> > do with the frontend, but just the BIU.
> > 
> > Some thought that i have, at present go like this
> > 
> > * register independant virtual buses for each device, on device
> > access, the relevant control word is appended to the BIU device
> > register.
> 
> Imho this is the preferred way. The master_xfer function of the virtual
> i2c bus could setup the BCU switch, then call master_xfer of the
> physical i2c bus.

I second this idea. Exactly like this is how I did with the dib7000/3000 
and the mt2060. It is the best and cleanest approach IMHO.

Patrick.




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