Re: [PATCH RFC v2 1/2] platform/x86: quickstart: Add ACPI quickstart button (PNP0C32) driver

["Barnabás Pőcze" <pobrn@protonmail.com>]

Hi

2022. szeptember 22., csütörtök 20:24 keltezéssel, Arvid Norlander írta:

> This is loosely based on a previous staging driver that was removed. See
> links below for more info on that driver. The original commit ID was
> 0be013e3dc2ee79ffab8a438bbb4e216837e3d52.
> 
> However, here a completely different approach is taken to the user space
> API (which should solve the issues the original driver had). Each PNP0C32
> device is a button, and each such button gets a separate input device
> associated with it (instead of a shared platform input device).
> 
> The button ID (as read from ACPI method GHID) is provided via a sysfs file
> "button_id".
> 
> If the button caused a wakeup it will "latch" the "wakeup_cause" sysfs file
> to true. This can be reset by a user space process.
> 
> Link: https://marc.info/?l=linux-acpi&m=120550727131007
> Link: https://lkml.org/lkml/2010/5/28/327
> Signed-off-by: Arvid Norlander <lkml@vorpal.se>
> ---
> [...]
> diff --git a/drivers/platform/x86/quickstart.c b/drivers/platform/x86/quickstart.c
> new file mode 100644
> index 000000000000..ce51abe012f7
> --- /dev/null
> +++ b/drivers/platform/x86/quickstart.c
> @@ -0,0 +1,320 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + *  quickstart.c - ACPI Direct App Launch driver
> + *
> + *  Copyright (C) 2022 Arvid Norlander <lkml@vorapal.se>
> + *  Copyright (C) 2007-2010 Angelo Arrifano <miknix@gmail.com>
> + *
> + *  Information gathered from disassembled dsdt and from here:
> + *  <https://archive.org/details/microsoft-acpi-dirapplaunch>
> + *
> + *  This program is free software; you can redistribute it and/or modify
> + *  it under the terms of the GNU General Public License as published by
> + *  the Free Software Foundation; either version 2 of the License, or
> + *  (at your option) any later version.
> + *
> + *  This program is distributed in the hope that it will be useful,
> + *  but WITHOUT ANY WARRANTY; without even the implied warranty of
> + *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + *  GNU General Public License for more details.
> + *
> + */
> +
> +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> +
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/init.h>
> +#include <linux/types.h>
> +#include <linux/acpi.h>
> +#include <linux/platform_device.h>
> +#include <linux/input.h>
> +#include <linux/input/sparse-keymap.h>
> +#include <asm/unaligned.h>
> +
> +MODULE_AUTHOR("Arvid Norlander <lkml@vorpal.se>");
> +MODULE_AUTHOR("Angelo Arrifano");
> +MODULE_DESCRIPTION("ACPI Direct App Launch driver");
> +MODULE_LICENSE("GPL");
> +
> +#define QUICKSTART_ACPI_DEVICE_NAME	"quickstart"
> +#define QUICKSTART_ACPI_HID		"PNP0C32"
> +
> +/*
> + * There will be two events:
> + * 0x02 - A hot button was pressed while device was off/sleeping.
> + * 0x80 - A hot button was pressed while device was up.
> + */
> +#define QUICKSTART_EVENT_WAKE		0x02
> +#define QUICKSTART_EVENT_RUNTIME	0x80
> +
> +/*
> + * Each PNP0C32 device is an individual button. This structure
> + * keeps track of data associated with said device.
> + */
> +struct quickstart_acpi {
> +	struct platform_device *platform_dev;
> +	struct input_dev *input_device;
> +	struct quickstart_button *button;
> +	/* ID of button as returned by GHID */
> +	u32 id;
> +	/* Name of input device */
> +	char input_name[32];
> +	/* Physical path for the input device */
> +	char phys[32];
> +	/* Track if a wakeup event was received */
> +	bool wakeup_cause;
> +};
> +
> +#define quickstart_name(dev) acpi_device_bid(dev->acpi_dev)

This does not seem to be used.


> +
> +/*
> + * Knowing what these buttons do require system specific knowledge.
> + * This could be done by matching on DMI data in a long quirk table.
> + * However, it is easier to leave it up to user space to figure this out.
> + *
> + * Using for example udev hwdb the scancode 0x1 can be remapped suitably.
> + */
> +static const struct key_entry quickstart_keymap[] = {
> +	{ KE_KEY, 0x1, { KEY_UNKNOWN } },
> +	{ KE_END, 0 },
> +};
> +
> +static ssize_t wakeup_cause_show(struct device *dev,
> +				 struct device_attribute *attr, char *buf)
> +{
> +	struct quickstart_acpi *quickstart = dev_get_drvdata(dev);
> +
> +	return sysfs_emit(buf, "%s\n",
> +			  (quickstart->wakeup_cause ? "true" : "false"));
> +}
> +
> +static ssize_t wakeup_cause_store(struct device *dev,
> +				  struct device_attribute *attr,
> +				  const char *buf, size_t count)
> +{
> +	struct quickstart_acpi *quickstart = dev_get_drvdata(dev);
> +
> +	if (count < 2)
> +		return -EINVAL;
> +
> +	if (strncasecmp(buf, "false", 4) != 0)
> +		return -EINVAL;
> +

If "true"/"false" will be used in the final version, then I think this check
currently is too lax. You could use `sysfs_streq()`. And I think the `count < 2`
check is not needed.


> +	quickstart->wakeup_cause = false;
> +	return count;
> +}
> +static DEVICE_ATTR_RW(wakeup_cause);
> +
> +static ssize_t button_id_show(struct device *dev, struct device_attribute *attr,
> +			      char *buf)
> +{
> +	struct quickstart_acpi *quickstart = dev_get_drvdata(dev);
> +
> +	return sysfs_emit(buf, "%u\n", quickstart->id);
> +}
> +static DEVICE_ATTR_RO(button_id);
> +
> +/* ACPI Driver functions */
> +static void quickstart_acpi_notify(acpi_handle handle, u32 event, void *context)
> +{
> +	struct platform_device *device = context;
> +	struct quickstart_acpi *quickstart = dev_get_drvdata(&device->dev);
> +
> +	if (!quickstart)
> +		return;
> +
> +	switch (event) {
> +	case QUICKSTART_EVENT_WAKE:
> +		quickstart->wakeup_cause = true;
> +		break;
> +	case QUICKSTART_EVENT_RUNTIME:
> +		if (!sparse_keymap_report_event(quickstart->input_device, 0x1,
> +						1, true)) {
> +			pr_info("Key handling error\n");

I don't think this branch can ever be taken.


> +		}
> +		break;
> +	default:
> +		pr_err("Unexpected ACPI event notify (%u)\n", event);

I think `dev_{err,info}()` should be preferred.


> +		break;
> +	}
> +}
> +
> +/*
> + * The GHID ACPI method is used to indicate the "role" of the button.
> + * However, all the meanings of these values are vendor defined.
> + *
> + * We do however expose this value to user space.
> + */
> +static int quickstart_acpi_ghid(struct quickstart_acpi *quickstart)
> +{
> +	acpi_handle handle = ACPI_HANDLE(&quickstart->platform_dev->dev);
> +	acpi_status status;
> +	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +	int ret = 0;
> +	union acpi_object *obj = NULL;
> +
> +	/*
> +	 * This returns a buffer telling the button usage ID,
> +	 * and triggers pending notify events (The ones before booting).
> +	 */
> +	status = acpi_evaluate_object(handle, "GHID", NULL, &buffer);
> +	if (ACPI_FAILURE(status)) {
> +		dev_err(&quickstart->platform_dev->dev,
> +			"GHID method failed, ACPI status %u\n", status);
> +		return -EINVAL;
> +	}
> +	obj = buffer.pointer;
> +
> +	/*
> +	 * GHID returns buffers, sanity check that is the case.
> +	 */
> +	if (obj->type != ACPI_TYPE_BUFFER) {
> +		dev_err(&quickstart->platform_dev->dev,
> +			"GHID did not return buffer\n");
> +		ret = -EINVAL;
> +		goto free_and_return;
> +	}
> +
> +	/*
> +	 * Quoting the specification:
> +	 * "The GHID method can return a BYTE, WORD, or DWORD.
> +	 *  The value must be encoded in little-endian byte
> +	 *  order (least significant byte first)."
> +	 */
> +	switch (obj->buffer.length) {
> +	case 1:
> +		quickstart->id = *(u8 *)obj->buffer.pointer;
> +		break;
> +	case 2:
> +		quickstart->id = get_unaligned_le16(obj->buffer.pointer);
> +		break;
> +	case 4:
> +		quickstart->id = get_unaligned_le32(obj->buffer.pointer);
> +		break;
> +	case 8:
> +		quickstart->id = get_unaligned_le64(obj->buffer.pointer);
> +		break;
> +	default:
> +		dev_err(&quickstart->platform_dev->dev,
> +			"GHID method returned buffer of unexpected length %lu\n",
> +			(unsigned long)obj->buffer.length);
> +		ret = -EINVAL;
> +		break;
> +	}
> +
> +free_and_return:
> +	kfree(buffer.pointer);
> +
> +	return ret;
> +}
> +
> +static struct attribute *quickstart_attributes[] = {
> +	&dev_attr_wakeup_cause.attr,
> +	&dev_attr_button_id.attr,
> +	NULL,
> +};
> +
> +static const struct attribute_group quickstart_attr_group = {
> +	.attrs = quickstart_attributes,
> +};
> +
> +static int quickstart_remove(struct platform_device *device)
> +{
> +	acpi_handle handle = ACPI_HANDLE(&device->dev);
> +
> +	acpi_remove_notify_handler(handle, ACPI_DEVICE_NOTIFY,
> +				   quickstart_acpi_notify);
> +
> +	return 0;
> +}
> +
> +static int quickstart_probe(struct platform_device *device)
> +{
> +	int ret;
> +	acpi_handle handle = ACPI_HANDLE(&device->dev);
> +	acpi_status status;
> +	struct quickstart_acpi *quickstart;
> +
> +	if (!device)
> +		return -EINVAL;
> +
> +	quickstart =
> +		devm_kzalloc(&device->dev, sizeof(*quickstart), GFP_KERNEL);
> +	if (!quickstart)
> +		return -ENOMEM;
> +
> +	/*
> +	 * This must be set early for proper cleanup on error handling path.
> +	 * After this point generic error handling can be used.
> +	 */
> +	quickstart->platform_dev = device;
> +	dev_set_drvdata(&device->dev, quickstart);
> +
> +	/* Retrieve the GHID ID */
> +	ret = quickstart_acpi_ghid(quickstart);
> +	if (ret < 0)
> +		goto error;

You can replace all `goto`s in this function with `return`s. In fact, you should
because `quickstart_remove()` does not do useful work until the ACPI notify handler
is registered, but if that succeeds, this function can no longer fail.


> +
> +	/* Set up sysfs entries */
> +	ret = devm_device_add_group(&quickstart->platform_dev->dev,
> +				    &quickstart_attr_group);

In the meantime I realized there is a simpler solution. Use the `ATTRIBUTE_GROUPS()`
macro and then simply set the `.dev_groups` member of `quickstart_platform_driver.driver`.
(see drivers/platform/x86/hp-wmi.c)


> +	if (ret) {
> +		dev_err(&device->dev, "Unable to setup sysfs entries\n");
> +		goto error;
> +	}
> +
> +	/* Set up input device */
> +	quickstart->input_device =
> +		devm_input_allocate_device(&quickstart->platform_dev->dev);
> +	if (!quickstart->input_device) {
> +		ret = -ENOMEM;
> +		goto error;
> +	}
> +	ret = sparse_keymap_setup(quickstart->input_device, quickstart_keymap,
> +				  NULL);
> +	if (ret)
> +		goto error;
> +
> +	snprintf(quickstart->input_name, sizeof(quickstart->phys),
> +		 "Quickstart Button %u", quickstart->id);
> +	snprintf(quickstart->phys, sizeof(quickstart->phys),
> +		 QUICKSTART_ACPI_DEVICE_NAME "/input%u", quickstart->id);
> +
> +	quickstart->input_device->name = quickstart->input_name;
> +	quickstart->input_device->phys = quickstart->phys;
> +	quickstart->input_device->id.bustype = BUS_HOST;
> +
> +	ret = input_register_device(quickstart->input_device);
> +
> +	/* Set up notify handler */
> +	status = acpi_install_notify_handler(handle, ACPI_DEVICE_NOTIFY,
> +					     quickstart_acpi_notify, device);
> +	if (ACPI_FAILURE(status)) {
> +		dev_err(&device->dev, "Error installing notify handler\n");
> +		return -EIO;
> +	}
> +
> +	return 0;
> +error:
> +	quickstart_remove(device);
> +	return ret;
> +}
> +
> +static const struct acpi_device_id quickstart_device_ids[] = {
> +	{ QUICKSTART_ACPI_HID, 0 },
> +	{ "", 0 },

Small thing, but usually the comma after the sentinel entry is omitted.
(see quickstart_keymap, quickstart_attributes as well)


> +};
> +MODULE_DEVICE_TABLE(acpi, quickstart_device_ids);
> +
> +static struct platform_driver quickstart_platform_driver = {
> +	.probe	= quickstart_probe,
> +	.remove	= quickstart_remove,
> +	.driver	= {
> +		.name = QUICKSTART_ACPI_DEVICE_NAME,
> +		.acpi_match_table = quickstart_device_ids,
> +		.owner = THIS_MODULE,
> +	}
> +};
> +
> +module_platform_driver(quickstart_platform_driver);
> --
> 2.37.3


Regards,
Barnabás Pőcze