[linux-dvb] Re: CX88 i2c issue w/ DVB tuners

[Ralph Metzler <rjkm@metzlerbros.de>]

Andrew de Quincey writes:
 > On Friday 10 Sep 2004 11:02, John Dalgliesh wrote:
 > > On Fri, 10 Sep 2004, Andrew de Quincey wrote:
 > > > On Thursday 09 Sep 2004 23:41, Gerd Knorr wrote:
 > > > > > Just hope there isn't a card out there with both DVB AND analogue
 > > > > > tuners on it....
 > > > >
 > > > > class isn't a value but a bitmask, so you can actually say the card
 > > > > can do both analog and digital tv ...
 > > >
 > > > Ah right cool. Eurgh, nasty problem waiting down the line when those
 > > > cards Holger mentioned appear.
 > >
 > > I don't think I understand the condition you are worried about. Do you
 > > mean that the card has to have two separate (i2c-addressable) tuners, one
 > > for analogue and one for digital? Or would a card that has one tuner that
 > > does both like <http://www.dvico.com/products_mul_hd3.html> be a worry?
 > >
 > > Just wondering :)
 > 
 > If the card is marked as both analogue and digital, and happens to use one of 
 > the i2c addresses which several devices use, you could end up with the wrong 
 > i2c device associated with the wrong device - e.g. the tda9987 (analogue 
 > tuner) driver was being used incorrectly as the driver for the cx22702 
 > (digtial demodulator) because they both commonly reside at the same i2c 
 > address. And theres no way to detect the tda9887 more specifically.

I think before (a year or so ago) when possible improvements 
of the kernel i2c driver for DVB were discussed on this list 
one of the ideas was to add a type field to the i2c client. 
Something like I2C_DVB_DEMOD, I2C_DVB_TUNER, I2C_ANALOG_TUNER, 
I2C_ANALOG_SOUND_THINGY_GADGET, etc.
The i2c driver could then choose in the attach function what kind of
clients to accept and how to configure them.


Ralph