[linux-dvb] Re: refactoring

[Holger Waechtler <holger@qanu.de>]

Andrew de Quincey wrote:

> On Monday 11 Oct 2004 13:14, Johannes Stezenbach wrote:
>  
> > 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.)
> >    
> Urgh, there is no nice solution to this. What is the least nasty?
>  
implement it in the card driver, this one can access all devices:

* first power down LNB, Switches and DiSEqC bus
* shut down PLL and demod via i2c
* shut down the i2c bus
* shut down the PCI bridge/USB transceiver, everything else

resume would get executed in the reverse order.

Holger