Re: monitor detection through ddc/edid stuff.

[Kronos <kronos@people.it>]

Il Fri, Sep 10, 2004 at 01:16:27PM +0200, Sven Luther ha scritto: 
> I also have quickly overviewed the radeon driver, which has a function to read
> the EDID either from the BIOS or the pmac OF. There seem to be no code
> whatsoever that adds proper EDID reading through the graphic card directly,
> like it is done in XFree86, where one can do in the individual drivers (using
> i2c stuff also) :
> 
> 	...
> 	pBus->BusName = "DDC";
> 	pBus->I2CUDelay = WildcatVPI2CUDelay;
> 	pBus->I2CPutBits = WildcatVPI2CPutBits;
> 	pBus->I2CGetBits = WildcatVPI2CGetBits;
>
> These three being smallish functions to delay a bit, and to put/get bits in
> the DCC Clock/Data Out/In registers.

Ok, you a have a bit-style adapter. i2c kernel core needs function to
control SDA and SCL but they can be easily created from X functions.

*GetBits must be splited in getscl (read clock) and getsda (get data),
and *PutBits must be splited in setscl and setsda.

I've done that with the radeon driver, look at drivers/video/aty/radeon_i2c.c.

> Would it make sense to implement such a feature in fbmon.c ? Is fbmon.c the
> right place for this ? Is this already implemented somewhere else, or maybe in
> some private tree somewhere ?

We already have a I2C subsystem, all you have to do is create a new
adapter and read from it (ie. you put the starting address on bus and
start reading).

> As i understand this, we would need some place to set the those three
> function, and then a common function to actually do a real EDID reading
> through the graphic card (get_EDID_from_harware ?).

Well, instead of PutBits/GetBits we have 4 functions, the algorithm is 
provided by the i2c subsystem. Look at radeon_do_probe_i2c_edid in the
radeon driver, it's not hard to do.

Oh, radeon_probe_i2c_connector contains some "black magic" to wakeup
some older boards/monitor. An ATI developer confirmed that it's needed
to cover some corner case, probably you don't need that on your board.

Luca
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