[PATCH v2 10/12] platform/x86: lenovo-wmi-capdata: Do not match missing components

[Rong Zhang]

Some devices do not support LENOVO_CAPABILITY_DATA_01. They either do
not have the corresponding WMI GUID, or do not implement the query
method.

In both cases, the WMI core does not create the corresponding WMI
device, leaving the component master (i.e., lenovo-wmi-other) waits for
the missing component forever.

Identify missing components using the new wmidev_exists() interface, and
skip adding them to the match list, so that all components in the list
must present, fulfilling the binding requirement.

Reported-by: Navon John Lukose <navonjohnlukose@xxxxxxxxx>
Closes: https://msgid.link/20260928190901.1369497-1-navonjohnlukose@xxxxxxxxx
Suggested-by: Mark Pearson <mpearson-lenovo@xxxxxxxxx>
Link: https://msgid.link/9789f452-d7eb-4f1e-8a13-7335332193a7@xxxxxxxxxxxxxxxx
Signed-off-by: Rong Zhang <i@xxxxxxxx>
---
Changes in v2:
- New patch in the series to solve the report made by Navon
---
 drivers/platform/x86/lenovo/wmi-capdata.c | 36 +++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

diff --git a/drivers/platform/x86/lenovo/wmi-capdata.c b/drivers/platform/x86/lenovo/wmi-capdata.c
index 79c72717ea40..6d98003539a7 100644
--- a/drivers/platform/x86/lenovo/wmi-capdata.c
+++ b/drivers/platform/x86/lenovo/wmi-capdata.c
@@ -49,6 +49,7 @@
 #include <linux/stddef.h>
 #include <linux/string.h>
 #include <linux/types.h>
+#include <linux/uuid.h>
 #include <linux/wmi.h>
 
 #include <asm/barrier.h>
@@ -75,14 +76,19 @@ enum lwmi_cd_type {
 	CD_TYPE_NONE = -1,
 };
 
-#define LWMI_CD_TABLE_ITEM(_type)		\
-	[_type] = {				\
-		.name = #_type,			\
-		.type = _type,			\
+static const struct wmi_device_id lwmi_cd_id_table[];
+
+/* Save some .rodata space by reusing the GUID strings from the id table. */
+#define LWMI_CD_TABLE_ITEM(_type)					\
+	[_type] = {							\
+		.name = #_type,						\
+		.guid_string = lwmi_cd_id_table[_type].guid_string,	\
+		.type = _type,						\
 	}
 
 static const struct lwmi_cd_info {
 	const char *name;
+	const char *guid_string;
 	enum lwmi_cd_type type;
 } lwmi_cd_table[] = {
 	LWMI_CD_TABLE_ITEM(LENOVO_CAPABILITY_DATA_00),
@@ -155,24 +161,46 @@ static int lwmi_cd_match(struct device *dev, void *type)
  *
  * Adds all component matches to the list stored in @matchptr for the @master
  * device. @matchptr must be initialized to NULL.
+ *
+ * Missing components are not added to the match list, or else the master waits
+ * for them forever. For some components, their existence can be determined by
+ * querying other components, so they are handled as sub-components and thus not
+ * matched here. For components with no existence declaration, wmidev_exists()
+ * is used to determine their existence.
+ *
+ * If all components are missing, ERR_PTR(-ENXIO) is returned through @matchptr.
  */
 void lwmi_cd_match_add_all(struct device *master, struct component_match **matchptr)
 {
+	bool matched = false;
 	int i;
 
 	if (WARN_ON(*matchptr))
 		return;
 
 	for (i = 0; i < ARRAY_SIZE(lwmi_cd_table); i++) {
+		guid_t guid;
+
 		/* Skip sub-components. */
 		if (lwmi_cd_table[i].type == LENOVO_FAN_TEST_DATA)
 			continue;
 
+		if (WARN_ON(guid_parse(lwmi_cd_table[i].guid_string, &guid)))
+			return;
+
+		if (!wmidev_exists(&guid))
+			continue;
+
 		component_match_add(master, matchptr, lwmi_cd_match,
 				    (void *)&lwmi_cd_table[i].type);
 		if (IS_ERR(*matchptr))
 			return;
+
+		matched = true;
 	}
+
+	if (!matched)
+		*matchptr = ERR_PTR(-ENXIO);
 }
 EXPORT_SYMBOL_NS_GPL(lwmi_cd_match_add_all, "LENOVO_WMI_CAPDATA");
 

-- 
2.55.0