[PATCH v4 1/2] firmware_loader: Add cancel helper for async requests

[Cássio Gabriel]

request_firmware_nowait() keeps the callback module pinned and holds
a device reference until the firmware work completes.

Callers still have no way to cancel or synchronize the queued callback
before tearing down their driver-private state.

Track scheduled async firmware work in an internal list and add
request_firmware_nowait_cancel(). The helper cancels work matching the
device, callback context and callback function. It cancels work that has
not started yet and waits for an already-running callback to return. If
the request has already completed, it is a no-op.

Keep the existing request_firmware_nowait() lifetime model manual. A
devres-managed variant can be layered on top separately if needed.

Signed-off-by: Cássio Gabriel <cassiogabrielcontato@xxxxxxxxx>
---
 drivers/base/firmware_loader/main.c | 68 ++++++++++++++++++++++++++++++++++---
 include/linux/firmware.h            | 10 ++++++
 2 files changed, 74 insertions(+), 4 deletions(-)

diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index a11b30dda23b..78c5f05a2ec1 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -1132,6 +1132,7 @@ EXPORT_SYMBOL(release_firmware);
 /* Async support */
 struct firmware_work {
 	struct work_struct work;
+	struct list_head list;
 	struct module *module;
 	const char *name;
 	struct device *device;
@@ -1140,6 +1141,17 @@ struct firmware_work {
 	u32 opt_flags;
 };
 
+static LIST_HEAD(firmware_work_list);
+static DEFINE_SPINLOCK(firmware_work_lock);
+
+static void firmware_work_free(struct firmware_work *fw_work)
+{
+	put_device(fw_work->device); /* taken in request_firmware_nowait() */
+	module_put(fw_work->module);
+	kfree_const(fw_work->name);
+	kfree(fw_work);
+}
+
 static void request_firmware_work_func(struct work_struct *work)
 {
 	struct firmware_work *fw_work;
@@ -1150,11 +1162,15 @@ static void request_firmware_work_func(struct work_struct *work)
 	_request_firmware(&fw, fw_work->name, fw_work->device, NULL, 0, 0,
 			  fw_work->opt_flags);
 	fw_work->cont(fw, fw_work->context);
-	put_device(fw_work->device); /* taken in request_firmware_nowait() */
 
-	module_put(fw_work->module);
-	kfree_const(fw_work->name);
-	kfree(fw_work);
+	spin_lock_irq(&firmware_work_lock);
+	if (!list_empty(&fw_work->list)) {
+		list_del_init(&fw_work->list);
+		spin_unlock_irq(&firmware_work_lock);
+		firmware_work_free(fw_work);
+		return;
+	}
+	spin_unlock_irq(&firmware_work_lock);
 }
 
 
@@ -1164,6 +1180,7 @@ static int _request_firmware_nowait(
 	void (*cont)(const struct firmware *fw, void *context), bool nowarn)
 {
 	struct firmware_work *fw_work;
+	unsigned long flags;
 
 	fw_work = kzalloc_obj(struct firmware_work, gfp);
 	if (!fw_work)
@@ -1196,7 +1213,12 @@ static int _request_firmware_nowait(
 
 	get_device(fw_work->device);
 	INIT_WORK(&fw_work->work, request_firmware_work_func);
+
+	spin_lock_irqsave(&firmware_work_lock, flags);
+	list_add_tail(&fw_work->list, &firmware_work_list);
 	schedule_work(&fw_work->work);
+	spin_unlock_irqrestore(&firmware_work_lock, flags);
+
 	return 0;
 }
 
@@ -1259,6 +1281,44 @@ int firmware_request_nowait_nowarn(
 }
 EXPORT_SYMBOL_GPL(firmware_request_nowait_nowarn);
 
+/**
+ * request_firmware_nowait_cancel() - cancel an async firmware request
+ * @device: device for which the firmware is being loaded
+ * @context: context passed to request_firmware_nowait()
+ * @cont: callback passed to request_firmware_nowait()
+ *
+ * Cancel a pending request_firmware_nowait() request for @device, @context
+ * and @cont. If the associated work has already started, this function waits
+ * until the callback has returned. If the callback has already completed, this
+ * function does nothing.
+ *
+ * This function may sleep.
+ */
+void request_firmware_nowait_cancel(struct device *device, void *context,
+				    void (*cont)(const struct firmware *fw,
+						 void *context))
+{
+	struct firmware_work *fw_work = NULL;
+	struct firmware_work *tmp;
+
+	spin_lock_irq(&firmware_work_lock);
+	list_for_each_entry_reverse(tmp, &firmware_work_list, list) {
+		if (tmp->device == device && tmp->context == context &&
+		    tmp->cont == cont) {
+			fw_work = tmp;
+			list_del_init(&fw_work->list);
+			break;
+		}
+	}
+	spin_unlock_irq(&firmware_work_lock);
+
+	if (!fw_work)
+		return;
+	cancel_work_sync(&fw_work->work);
+	firmware_work_free(fw_work);
+}
+EXPORT_SYMBOL_GPL(request_firmware_nowait_cancel);
+
 #ifdef CONFIG_FW_CACHE
 static ASYNC_DOMAIN_EXCLUSIVE(fw_cache_domain);
 
diff --git a/include/linux/firmware.h b/include/linux/firmware.h
index aae1b85ffc10..0fa3b027f02f 100644
--- a/include/linux/firmware.h
+++ b/include/linux/firmware.h
@@ -110,6 +110,9 @@ int request_firmware_nowait(
 	struct module *module, bool uevent,
 	const char *name, struct device *device, gfp_t gfp, void *context,
 	void (*cont)(const struct firmware *fw, void *context));
+void request_firmware_nowait_cancel(struct device *device, void *context,
+				    void (*cont)(const struct firmware *fw,
+						 void *context));
 int request_firmware_direct(const struct firmware **fw, const char *name,
 			    struct device *device);
 int request_firmware_into_buf(const struct firmware **firmware_p,
@@ -157,6 +160,13 @@ static inline int request_firmware_nowait(
 	return -EINVAL;
 }
 
+static inline void request_firmware_nowait_cancel(struct device *device,
+						  void *context,
+						  void (*cont)(const struct firmware *fw,
+							       void *context))
+{
+}
+
 static inline void release_firmware(const struct firmware *fw)
 {
 }

-- 
2.54.0