[linux-dvb] Re: refactoring

[Johannes Stezenbach <js@linuxtv.org>]

On Mon, Oct 11, 2004 at 12:32:45PM +0100, Andrew de Quincey wrote:
> On Monday 11 Oct 2004 12:29, Johannes Stezenbach wrote:
> > Well, if the i2c bus and the devices on the bus aren't exposed
> > at all in sysfs, then the DVB adapter driver could take care
> > of it when called via PCI bus power management hooks. I don't
> > think this is a good design, but it would work for PCI cards.
> 
> I'm only talking about not exposing the bits of the frontend - exposing the 
> i2c bus is fine - you might have self-contained devices on it that it makes 
> sense for userspace to see (e.g. EEPROMs, analogue tv tuners).

Then I suspect we might run into problems when the power management
core decides to power down busses in the wrong order. Well, on PCI
cards one could make the i2c adapter shutdown a noop, and do the i2c
shutdown when the PCI adapter is shutdown. On embedded you have
no such luck. You must power down the demod/PLL before the
i2c bus goes to sleep. (There'll be probable ways to kludge
around this, but it will never be clean&simple.)

Johannes