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SubjectRe: [PATCH] HID: i2c-hid: Use device properties (instead of device tree)
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On Fri, 2017-09-29 at 15:44 -0700, Rajat Jain wrote:
> Use the device properties (that can be provided by ACPI systems
> as well as non ACPI systems) instead of device tree properties
> (that are not provided ACPI systems). This required some minor
> code restructuring.
>

> I don't think its a big deal, but just FYI, this changes the order in
> which we
> look for HID register address from
> (device tree -> platform_data -> ACPI) to
> (platform data -> device tree -> ACPI)

I do.

We would like to discourage use of legacy platform data in favour
of Device Tree / ACPI.

> +static int i2c_hid_fwnode_probe(struct i2c_client *client,
> struct i2c_hid_platform_data *pdata)
> {
> struct device *dev = &client->dev;
> u32 val;
> int ret;
>
> - ret = of_property_read_u32(dev->of_node, "hid-descr-addr",
> &val);
> - if (ret) {
> - dev_err(&client->dev, "HID register address not
> provided\n");
> - return -ENODEV;
> - }
> - if (val >> 16) {
> - dev_err(&client->dev, "Bad HID register address:
> 0x%08x\n",
> - val);
> - return -EINVAL;
> + ret = device_property_read_u32(dev, "hid-descr-addr", &val);
> + if (ret || val >> 16) {
> + /* Couldn't read using fwnode, try ACPI next */
> + if (!i2c_hid_acpi_pdata(client, pdata)) {
> + dev_err(dev, "Bad/Not provided HID register
> address\n");
> + return -ENODEV;
> + }

Why not just replace of_ calls by device_ ones?

> }
> pdata->hid_descriptor_address = val;
>
> - ret = of_property_read_u32(dev->of_node, "post-power-on-
> delay-ms",
> - &val);
> + ret = device_property_read_u32(dev, "post-power-on-delay-ms",
> &val);
> if (!ret)
> pdata->post_power_delay_ms = val;
>
> return 0;
> }
>

Looking how ACPI support is established in the driver, I would rather
NAK this change. Is there any _actual_ hardware on the wild with such
properties?

HID protocol for ACPI is described in [1] where nothing is about _DSD.

[1]: https://docs.microsoft.com/en-us/windows-hardware/drivers/hid/plug-
and-play-support-and-power-management

--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy

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