Hi Peter,
On Tue, 30 Nov 2010 15:03:08 +0100, Peter Korsgaard wrote:
> Add an i2c mux driver providing access to i2c bus segments using a
> hardware MUX sitting on a master bus and controlled through gpio pins.
>
> E.G. something like:
>
> ---------- ---------- Bus segment 1 - - - - -
> | | SCL/SDA | |-------------- | |
> | |------------| |
> | | | | Bus segment 2 | |
> | Linux | GPIO 1..N | MUX |--------------- Devices
> | |------------| | | |
> | | | | Bus segment M
> | | | |---------------| |
> ---------- ---------- - - - - -
>
> SCL/SDA of the master I2C bus is multiplexed to bus segment 1..M
> according to the settings of the GPIO pins 1..N.
I've fixed two remaining minor things myself, and your patch is ready
to be applied now, except for one issue I just noticed. See below.
> (..)
> --- /dev/null
> +++ b/Documentation/i2c/muxes/gpio-i2cmux
> (...)
> +Usage
> +-----
> +
> +gpio-i2cmux uses the platform bus, so you need to provide a struct
> +platform_device with the platform_data pointing to a struct
> +gpio_i2cmux_platform_data with the I2C adapter number of the master
> +bus, the number bus segments to create and the GPIO pins used
"of" got lost in the battle, I've added it back.
> +to control it. See include/linux/gpio-i2cmux.h for details.
> (...)
> --- /dev/null
> +++ b/drivers/i2c/muxes/gpio-i2cmux.c
> (...)
> + for (i = 0; i < pdata->n_gpios; i++) {
> + ret = gpio_request(pdata->gpios[i], "gpio-i2cmux");
> + if (ret)
> + goto err_request_gpio;
> + gpio_direction_output(pdata->gpios[i], pdata->idle & (1 << i));
This looks wrong if pdata->idle == GPIO_I2CMUX_NO_IDLE. I think we want
something along the lines of:
unsigned initial_state;
initial_state = pdata->idle == GPIO_I2CMUX_NO_IDLE ?
pdata->values[0] : pdata->idle;
(...)
gpio_direction_output(pdata->gpios[i], initial_state & (1 << i));
What do you think? An alternative is to leave the direction
uninitialized and hope it's already OK, but I'm not sure how realistic
this is.
> + }
> +
> +
Double blank line, I've removed one.
> + if (pdata->idle != GPIO_I2CMUX_NO_IDLE)
> + deselect = gpiomux_deselect;
--
Jean Delvare
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