[U-Boot-Users] Using a second I2C interface
Ben Warren
bwarren at qstreams.com
Tue May 16 15:50:17 CEST 2006
Wolfgang,
This sounds like a sensible approach. This should clean the code up
nicely (as you'll notice, the patch that I submitted yesterday adds
quite a bit of noisy code). Let's look at what Richard Woodruff
submits, and we can take it from there.
Too bad I didn't get your input until this morning, even though your
message went out on Friday...
regards,
Ben
On Fri, 2006-05-12 at 21:01 +0200, Wolfgang Denk wrote:
> Hello,
>
> in message <E541A453-EC07-4597-8D60-2EE3919C1A18 at kernel.crashing.org> you wrote:
> >
> > > The CPU I'm using (MPC8349) has two hardware I2C interfaces, and
> > > I'd like to access the second one in U-boot. Implementing this
> > > looks easy to me, but I don't want to reinvent the wheel if it's
> > > already been done elsewhere. Has anyone done this? If not, I'll
> > > follow up with a proposal.
> >
> > Depending on what you want to do, you can cheat and just change the
> > pointer to the 2nd interface. If you want something more full
> > featured up to the command level then I think some discussion would
> > be required on how the commands should work for specifying which
> > controller to use.
>
> A clean design should allow to switch I2C busses usign a command;
> additionally, I think we should try to stay backward-compatible with
> the existing code. Eventually this is not too difficult: similar to
> the "ide" or "usb" commands we could create a new command "i2c
> device" which takes as argument the number of the I2C bus which shal
> become the current (= active) bus. Then all existing I2C related
> commands can be left unchanged (and "i2c device" without arguments
> should of course print the ID of the current bus).
>
> In parallel, existing I2C commands could be changed to migrate to a
> new "i2c" group of commands: "imd" would become "i2c md", "imw"
> becomes "i2c mw", "iprobe" becomes "i2c probe", etc. For some (long)
> transition period old and new commands could be provided in parallel
> (at least optionally). Later, the old syntax could be dropped.
>
> Best regards,
>
> Wolfgang Denk
>
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