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

[Hans de Goede <hdegoede@redhat.com>]

Hi,

On 9/23/22 21:24, Barnabás Pőcze wrote:
> 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.

True, might just as well drop the if and simply call sparse_keymap_report_event()
without checking the result.

> 
> 
>> +		}
>> +		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)

Ack yes please, using .dev_groups is greatly preferred.

> 
> 
>> +	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
> 

Regards,

Hans