[PATCH v3 1/3] ACPI: EC: Limit explicit removal of query handlers to custom query handlers

[Armin Wolf <W_Armin@xxxxxx>]

According to the ACPI spec part 5.6.4.1.2, EC query handlers discovered
thru ACPI should not be removed when a driver removes his custom query
handler. On the Acer Travelmate 4002WLMi for example, such a query
handler is used as a fallback to handle the EC SMBus alert when no driver
is present.
Change acpi_ec_remove_query_handlers() so that only custom query
handlers are removed then remove_all is false. Query handlers discovered
thru ACPI will still get removed when remove_all is true, which happens
on device removal. Also add a simple check to ensure that
acpi_ec_add_query_handler() is always called with either handle or func
being set, since custom query handlers are detected based whether
handlers->func is set or not.

Tested on a Acer Travelmate 4002WLMi.

Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
---
 drivers/acpi/ec.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/drivers/acpi/ec.c b/drivers/acpi/ec.c
index 105d2e795afa..f84905dbd8ca 100644
--- a/drivers/acpi/ec.c
+++ b/drivers/acpi/ec.c
@@ -1083,9 +1083,12 @@ int acpi_ec_add_query_handler(struct acpi_ec *ec, u8 query_bit,
 			      acpi_handle handle, acpi_ec_query_func func,
 			      void *data)
 {
-	struct acpi_ec_query_handler *handler =
-	    kzalloc(sizeof(struct acpi_ec_query_handler), GFP_KERNEL);
+	struct acpi_ec_query_handler *handler;
+
+	if (!handle && !func)
+		return -EINVAL;

+	handler = kzalloc(sizeof(*handler), GFP_KERNEL);
 	if (!handler)
 		return -ENOMEM;

@@ -1097,6 +1100,7 @@ int acpi_ec_add_query_handler(struct acpi_ec *ec, u8 query_bit,
 	kref_init(&handler->kref);
 	list_add(&handler->node, &ec->list);
 	mutex_unlock(&ec->mutex);
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(acpi_ec_add_query_handler);
@@ -1109,9 +1113,15 @@ static void acpi_ec_remove_query_handlers(struct acpi_ec *ec,

 	mutex_lock(&ec->mutex);
 	list_for_each_entry_safe(handler, tmp, &ec->list, node) {
-		if (remove_all || query_bit == handler->query_bit) {
+		/* When remove_all is false, we only remove custom query handlers
+		 * which have handler->func set. This is done to preserve query
+		 * handlers discovered thru ACPI, as they should continue handling
+		 * EC queries.
+		 */
+		if (remove_all || (handler->func && handler->query_bit == query_bit)) {
 			list_del_init(&handler->node);
 			list_add(&handler->node, &free_list);
+
 		}
 	}
 	mutex_unlock(&ec->mutex);
--
2.30.2