Re: [PATCH 2/4] mmc: omap: adapt the hsmmc driver to device tree

[Rajendra Nayak <rnayak@ti.com>]

On Saturday 05 November 2011 02:55 AM, Cousson, Benoit wrote:
>>> +Required properties:
>>> +- compatible: Should be "ti,omap-hsmmc<n>", "ti,omap2-hsmmc";
>>> +n is controller instance starting 0, for OMAP2/3 controllers
>>
>> No, no, no. You should not have to specify the unit-address in the
>> compatible
>> field. They are all programmed the same way, right?
>
> AFAIR, 2 instances contain a DMA engine, but that should anyway be
> detected using a "ti,had-dma-engine" extra property and not like that.
>
> Checking the code in #2, it is used to get the instance of the MMC.
>
> +static unsigned int of_get_hsmmc_instance(struct device_node *np)
> +{
> +    int i;
> +    char comp[32];
> +
> +    for (; i < OMAP_MMC_DEV_MAX; i++) {
> +        snprintf(comp, 32, "ti,omap-hsmmc%d", i);
> +        if (of_device_is_compatible(np, comp))
> +            break;
> +    }
> +    return i;
> +}
>
> Which does not seems to be a good usage of the compatible property anyway.
> For a similar issue someone on the list suggested using the "cell-index"
> property. But the definition I found in some binding documentation seems
> to reserve that to: "enumerate logical devices within an IP core."
> Ideally the driver should probably get rid of the need for an index.
> I didn't check the original driver, but that should be needed for some
> legacy reason.

yes, there are a bunch of things done inside the driver based on the
instance id which seem wrong, but I agree, encoding the instance
in the compatible property seems really bad and non-scalable.
Will look at how some of this legacy code in the driver can be
removed/cleaned up.