Re: radeonfb monid i2c bus

[Jean Delvare <khali@linux-fr.org>]

Hi Alex,

Thanks for your answers.

On Mon, 9 Jun 2008 01:15:00 -0400, Alex Deucher wrote:
> On Sun, Jun 8, 2008 at 10:20 AM, Jean Delvare <khali@linux-fr.org> wrote:
> > But apparently not all chips have the "monid" bus? Or is it a card
> > property, and other cards using the same Radeon 9200 might have it
> > while mine doesn't? I wouldn't care about an empty i2c bus, but a
> > broken bus as I get now affects the whole i2c subsystem and its users
> > in unpleasant ways. That's why I am wondering if there's a way to avoid
> > it.
> 
> They are just gpio pads.  All the cards supported by radeonfb have
> then, but only certain ones are wired up as per the bios connector
> tables on x86 cards.  Mac cards and we currently hard code them based
> on lots of investigation.  I suppose, ideally, you check the connector
> tables and some of the other bios tables (powerplay, external tmds,
> ext dac, multimedia. etc.) and only init the buses you have a
> particular card.

That would indeed make sense. If these are GPIOs, do we even have any
guarantee that they aren't used for other purposes when not used for
I2C? I've always considered the monid I2C bus on my adapters to be
non-existent (i2c-algo-bit can't control the lines) and that's the
reason why I wanted it to not be created, but maybe the GPIO lines are
actually used for something different and creating the non-existent I2C
bus could break that?

So if it is possible to create the I2C buses (by default, at least)
only when the BIOS connector tables say they are present, I'm in favor
of doing that.

-- 
Jean Delvare

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