[linux-dvb] Re: Proposal for new frontend architecture

[Andrew de Quincey <adq_dvb@lidskialf.net>]

> One quirk with this is that there is a chicken-and-egg issue with cards
> which have config info in a i2c-connected eeprom chip.  Current bttv
> solves that by doing the TUNER_SET_TYPE thingy in two different places,
> once in the callback mentioned above and once after reading the eeprom
> to make sure it works with any module load order.  One fix for that I
> can think of is to separate adapter registering and bus scan, i.e.
> have something like
>
>  i2c_add_adapter_noprobe();
>  /* bttv can read the eeprom here */
>  i2c_adapter_probe_drivers();
>
> Additional benefit is that i2c adapters can bypass autoprobe altogether
> by simply not calling i2c_adapter_probe_drivers() ;)

I've been implementing this suggestion. One reason I prefer having a flag in 
the adapter (as opposed to i2c_add_adapter_noprobe()) is the following 
situation:

i2c_add_adapter_noprobe()
.... hardware communicates with EEPROM
.... in the meantime, another module is loaded which registers an i2c_driver 
with the I2C_DF_NOTIFY flag set - this will attempt to register this new 
driver with the the partially initialised adapter.
....

Also, if new i2c adapters are loaded post-initialisation, they will also try 
to register with the adapter in turn.

Having a flag means this situation cannot occur.