[PATCH 1/4] iio: mxs-lradc: separate touchscreen and buffer virtual channels

[Marek Vasut]

On Saturday, January 17, 2015 at 01:22:08 AM, Kristina Martšenko wrote:

Hi!

Good stuff, thank you! Just minor nitpicks below.

[...]

> diff --git a/drivers/staging/iio/adc/mxs-lradc.c
> b/drivers/staging/iio/adc/mxs-lradc.c index e0e91836eec1..fc65cd311be9
> 100644
> --- a/drivers/staging/iio/adc/mxs-lradc.c
> +++ b/drivers/staging/iio/adc/mxs-lradc.c
> @@ -214,11 +214,14 @@ struct mxs_lradc {
>  	unsigned long		is_divided;
> 
>  	/*
> -	 * Touchscreen LRADC channels receives a private slot in the CTRL4
> -	 * register, the slot #7. Therefore only 7 slots instead of 8 in the
> -	 * CTRL4 register can be mapped to LRADC channels when using the
> -	 * touchscreen.
> -	 *
> +	 * When the touchscreen is enabled, we give it two private virtual
> +	 * channels: #6 and #7. This means that only 6 virtual channels (instead
> +	 * of 8) will be available for buffered capture.
> +	 */
> +#define TS_VCH1		7
> +#define TS_VCH2		6

Please use a bit more explicit name for the macro, it's really not clear what
the macro represents from it's name. Something like TOUCHSCREEN_VCHANNEL1 might
work better for example. What do you think ?

> +
> +	/*
>  	 * Furthermore, certain LRADC channels are shared between touchscreen
>  	 * and/or touch-buttons and generic LRADC block. Therefore when using
>  	 * either of these, these channels are not available for the regular
[...]

I also have a general question/idea here, it's explicitly not something I'd like
to force upon you to implement. I see we have some kind of a hardware, which can
sample up-to N inputs in parallel . Each input is muxed between M possible 
sources . Is such a thing common in the ADC/DAC world ? Would it be worth to
implement generic helper to handle this kind of a N:M mapping ? What do you all
think please ?

Best regards,
Marek Vasut