Re: [PATCH v7 1/5] i2c: core: add callback to change bus frequency

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Mon, Feb 23, 2026 at 03:33:50PM +0100, Marcus Folkesson wrote:
> All devices on the same I2C bus share the same clock line and the bus
> frequency has therefor be chosen so that all attached devices are able
> to tolarate that clock rate. IOW, the bus speed must be set for the
> slowest attached device.
> 
> With I2C multiplexers/switches on the other hand, it would be possible
> to have different "domains" that runs with different speeds.
> 
> Prepare for such a feature by provide an optional callback function to
> change bus frequency.
> 
> As a side effect, several bus drivers keep the bus speed in a
> private structure and can now have this value stored in a uniform way
> instead.

...

> +	/*
> +	 * If the adapter is a root adapter without set_clk_freq implemented, this feature is not
> +	 * supported
> +	 */
> +	if (!i2c_parent_is_i2c_adapter(adapter))
> +		return -EOPNOTSUPP;
> +
> +	/* Update the clock_hz for non-root adapters, even if set_clk_freq is not implemented,
> +	 * to allow * the clock frequency to be propagated to root adapters that do support it.
> +	 */

/*
 * Please, keep the style of multi-line comment consistent
 * and as per above.
 */

> +	adapter->clock_hz = clock_hz;
> +	return 0;
> +}

-- 
With Best Regards,
Andy Shevchenko