On Thu, 2008-08-21 at 11:32 -0500, Scott Wood wrote:

On Thu, Aug 21, 2008 at 12:10:12AM -0700, David Miller wrote:

quoted

Mostly straightforward stuff _except_ for the I2C address encoding.

What I2C IEEE1275 device binding was used to write that code in
of_i2c.c?  Is it some PowerPC specific thing?  Was it "invented"
by the embedded folks (I hope not)?

Yes, it was "invented".  There was no documented i2c OF binding that I
could find, and AFAIR nobody came forward with examples of existing
practice at the time.

Well, there were examples in the powermac code :-)

quoted

And, furthermore, the device address is shifted up 1 bit higher
than the Linux I2C layer expects.  It includes the low direction
bit, bit 0, so we have to shift it down by 1 bit before we give
it to the Linux I2C layer.

Yuck.

Apple does the same. IE. I take the address from "reg" and shift it
right by one bit before passing it to linux.

quoted

2) When CONFIG_SPARC, shift the device address down by one bit before
   giving it to the Linux I2C layer.

Maybe we should distinguish by the type of I2C bus node instead.

Or fix the embedded stuff :-)

Ben.