Re: [PATCH 2/3 v2] ARM: bcm2835: Add the Raspberry Pi firmware driver

[Noralf TrÃnnes]

Den 13.05.2015 21:00, skrev Eric Anholt:
> This gives us a function for making mailbox property channel requests
> of the firmware, which is most notable in that it will let us get and
> set clock rates.
>
> Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
> ---

[...]

> +/*
> + * Submits a single tag to the VPU firmware through the mailbox
> + * property interface.
> + *
> + * This is a convenience wrapper around
> + * rpi_firmware_property_list() to avoid some of the
> + * boilerplate in property calls.
> + */
> +int rpi_firmware_property(struct device_node *of_node,
> +			  u32 tag, void *tag_data, size_t buf_size)

To use the firmware property functions, I need a DT node pointer.
Since Device Tree is dynamic now, should I fetch the firmware node
each time, or should I do that in probe and store the node pointer?

Device Tree:
        firmware: firmware {
            compatible = "raspberrypi,firmware";
        };

        thermal {
            compatible = "brcm,bcm2835-thermal";
            firmware = <&firmware>;
        };

Rewritten (not tested) function from downstream bcm2835-thermal driver:

static int bcm2835_get_temp_or_max(struct thermal_zone_device *thermal_dev,
                                   unsigned long *temp, unsigned tag_id)
{
    struct device *dev = <get device somehow>;
    struct device_node *np;
    struct {
        u32 id;
        u32 val;
    } tag_buf;

    np = of_parse_phandle(dev->of_node, "firmware", 0);
    if (!np)
        return -EINVAL;

    ret = rpi_firmware_property(np, tag_id, &tag_buf, sizeof(tag_buf));
    if (ret)
        return ret;

    *temp = val;

    return 0;
}

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