Re: [PATCH v2 2/4] Documentation: i2c: describe the new slave mode

["Uwe Kleine-König" <u.kleine-koenig@pengutronix.de>]

Hello Wolfram,

On Mon, Mar 23, 2015 at 09:26:37AM +0100, Wolfram Sang wrote:
> +Developer manual
> +========
> +
> +I2C slave events
> +----------------
> +
> +The bus driver sends an event to the backend using the following function:
> +
> +	ret = i2c_slave_event(client, event, &val)
> +
> +'client' describes the i2c slave device. 'event' is one of the special event
> +types described hereafter. 'val' holds an u8 value for the data byte to be
> +read/written and is thus bidirectional. The pointer to val must always be
> +provided even if val is not used for an event, i.e. don't use NULL here. 'ret'
> +is the return value from the backend. Mandatory events must be provided by the
I don't understand why you want to force a valid pointer here. According
to my sense of defensive programming I'd say: If the bus driver doesn't
expect the slave to consume/provide a value, let's pass NULL to notice
the assumption being wrong. The wording is fine, now.

> diff --git a/Documentation/i2c/summary b/Documentation/i2c/summary
> index 13ab076dcd9248..809541ab352f03 100644
> --- a/Documentation/i2c/summary
> +++ b/Documentation/i2c/summary
> @@ -41,7 +41,3 @@ integrated than Algorithm and Adapter.
>  
>  For a given configuration, you will need a driver for your I2C bus, and
>  drivers for your I2C devices (usually one driver for each device).
> -
> -At this time, Linux only operates I2C (or SMBus) in master mode; you can't
> -use these APIs to make a Linux system behave as a slave/device, either to
> -speak a custom protocol or to emulate some other device.
\o/

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
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