[i2c] mixed-speed I2C system

nishanth menon menon.nishanth at gmail.com
Tue Apr 3 01:44:58 CEST 2007


Hi Stanley,
On 4/2/07, Stanley Cai <stanley.w.cai at gmail.com> wrote:
> > Are you suggesting that the device registration also provide the device
> > speed and we program the i2c_clk speeds run-time (@ xfer_msg) as being
> > dependent on the device?
> max supported clock may be an attribute of i2c clients and i2c masters
> so the i2c framework can find out the correct clock for the whole i2c
> bus.
hmm.. two considerations:
1. How can a client tell the adapter of a maximum supported transfer
speed? esp since i2c-dev would use a direct i2c_msg transfer.
this could be an argument for having speed as a i2c_msg param..just a
suggestion..

2. What is the standard way of passing the maximum supported frequency
for a specific adaptor?
As a specific example of OMAP(the controller can support all
frequencies), I was thinking more of using resource array
(flags=IORESOURCE_IO) while registering a platform_device in the board
specific file.
a) if the adapter is capable, a range defined by .start and .end
b) specific speed support only (with a .end=400 or .end=3400).
This shall give the adaptor driver a means to limit msg speed requests.

>
> Russell King has added I2C slave support at least for PXA...
am ignorant here.. any links to the patch?

Thanks and regards,
Nishanth Menon



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