linux-kernel - [PATCH v2 1/5] platform/x86: wmi: Decouple probe deferring from wmi_block

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Message-Id: <20231020211005.38216-2-W_Armin@gmx.de>
Date:   Fri, 20 Oct 2023 23:10:01 +0200
From:   Armin Wolf <W_Armin@....de>
To:     hdegoede@...hat.com, ilpo.jarvinen@...ux.intel.com,
        markgross@...nel.org
Cc:     platform-driver-x86@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 1/5] platform/x86: wmi: Decouple probe deferring from wmi_block_list

Many aggregate WMI drivers do not use -EPROBE_DEFER when they
cannot find a WMI device during probe, instead they require
all WMI devices associated with an platform device to become
available at once. This is currently achieved by adding those
WMI devices to the wmi_block_list before they are registered,
which is then used by the deprecated GUID-based functions to
search for WMI devices.

Replace this approach with a device link which defers probing
of the WMI device until the associated platform device has finished
probing (and has registered all WMI devices). New aggregate WMI
drivers should not rely on this behaviour.

Signed-off-by: Armin Wolf <W_Armin@....de>
---
 drivers/platform/x86/wmi.c | 39 +++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/drivers/platform/x86/wmi.c b/drivers/platform/x86/wmi.c
index a78ddd83cda0..1dbef16acdeb 100644
--- a/drivers/platform/x86/wmi.c
+++ b/drivers/platform/x86/wmi.c
@@ -1221,6 +1221,26 @@ static int wmi_create_device(struct device *wmi_bus_dev,
 	return 0;
 }

+static int wmi_add_device(struct platform_device *pdev, struct wmi_device *wdev)
+{
+	struct device_link *link;
+
+	/*
+	 * Many aggregate WMI drivers do not use -EPROBE_DEFER when they
+	 * are unable to find a WMI device during probe, instead they require
+	 * all WMI devices associated with an platform device to become available
+	 * at once. This device link thus prevents WMI drivers from probing until
+	 * the associated platform device has finished probing (and has registered
+	 * all discovered WMI devices).
+	 */
+
+	link = device_link_add(&wdev->dev, &pdev->dev, DL_FLAG_AUTOREMOVE_SUPPLIER);
+	if (!link)
+		return -EINVAL;
+
+	return device_add(&wdev->dev);
+}
+
 static void wmi_free_devices(struct acpi_device *device)
 {
 	struct wmi_block *wblock, *next;
@@ -1263,11 +1283,12 @@ static bool guid_already_parsed_for_legacy(struct acpi_device *device, const gui
 /*
  * Parse the _WDG method for the GUID data blocks
  */
-static int parse_wdg(struct device *wmi_bus_dev, struct acpi_device *device)
+static int parse_wdg(struct device *wmi_bus_dev, struct platform_device *pdev)
 {
+	struct acpi_device *device = ACPI_COMPANION(&pdev->dev);
 	struct acpi_buffer out = {ACPI_ALLOCATE_BUFFER, NULL};
 	const struct guid_block *gblock;
-	struct wmi_block *wblock, *next;
+	struct wmi_block *wblock;
 	union acpi_object *obj;
 	acpi_status status;
 	int retval = 0;
@@ -1317,22 +1338,14 @@ static int parse_wdg(struct device *wmi_bus_dev, struct acpi_device *device)
 			wblock->handler = wmi_notify_debug;
 			wmi_method_enable(wblock, true);
 		}
-	}

-	/*
-	 * Now that all of the devices are created, add them to the
-	 * device tree and probe subdrivers.
-	 */
-	list_for_each_entry_safe(wblock, next, &wmi_block_list, list) {
-		if (wblock->acpi_device != device)
-			continue;
-
-		retval = device_add(&wblock->dev.dev);
+		retval = wmi_add_device(pdev, &wblock->dev);
 		if (retval) {
 			dev_err(wmi_bus_dev, "failed to register %pUL\n",
 				&wblock->gblock.guid);
 			if (debug_event)
 				wmi_method_enable(wblock, false);
+
 			list_del(&wblock->list);
 			put_device(&wblock->dev.dev);
 		}
@@ -1487,7 +1500,7 @@ static int acpi_wmi_probe(struct platform_device *device)
 	}
 	dev_set_drvdata(&device->dev, wmi_bus_dev);

-	error = parse_wdg(wmi_bus_dev, acpi_device);
+	error = parse_wdg(wmi_bus_dev, device);
 	if (error) {
 		pr_err("Failed to parse WDG method\n");
 		goto err_remove_busdev;
--
2.39.2