[linux-dvb] bus control

Oliver Endriss o.endriss at gmx.de
Mon Jul 23 19:38:55 CEST 2007


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.

This way any existing frontend driver might be used without
modification. (Don't know if this is important.)

CU
Oliver

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