[PATCH v2 1/3] firmware loader: Introduce new API - request_firmware_abort()

[Kweh Hock Leong <hock.leong.kweh@intel.com>]

From: "Kweh, Hock Leong" <hock.leong.kweh@intel.com>

Besides aborting through user helper interface, a new API
request_firmware_abort() allows kernel driver module to abort the
request_firmware() / request_firmware_nowait() when they are no
longer needed. It is useful for cancelling an outstanding firmware
load if initiated from inside a module where that module is in the
process of being unloaded, since the unload function may not have
a handle to the struct firmware_buf.

Note for people who use request_firmware_nowait():
You are required to do your own synchronization after you call
request_firmware_abort() in order to continue unloading the
module. The example synchronization code shows below:

while (THIS_MODULE && module_refcount(THIS_MODULE))
	msleep(20);

Cc: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Kweh, Hock Leong <hock.leong.kweh@intel.com>
---
 drivers/base/firmware_class.c |   52 +++++++++++++++++++++++++++++++----------
 include/linux/firmware.h      |    4 ++++
 2 files changed, 44 insertions(+), 12 deletions(-)

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index d276e33..a238a46 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -1291,6 +1291,46 @@ request_firmware_nowait(
 }
 EXPORT_SYMBOL(request_firmware_nowait);
 
+static struct firmware_buf *fw_lookup_buf(const char *fw_name)
+{
+	struct firmware_buf *tmp;
+	struct firmware_cache *fwc = &fw_cache;
+
+	spin_lock(&fwc->lock);
+	tmp = __fw_lookup_buf(fw_name);
+	spin_unlock(&fwc->lock);
+
+	return tmp;
+}
+
+/**
+ * request_firmware_abort - abort the waiting of firmware request
+ * @fw_name: name of firmware file
+ *
+ *	@fw_name is the same name string while calling to request_firmware()
+ *		or request_firmware_nowait().
+ **/
+int request_firmware_abort(const char *fw_name)
+{
+	struct firmware_buf *buf;
+	struct firmware_buf *entry;
+
+	buf = fw_lookup_buf(fw_name);
+	if (!buf)
+		return -ENOENT;
+
+	mutex_lock(&fw_lock);
+	list_for_each_entry(entry, &pending_fw_head, pending_list) {
+		if (entry == buf) {
+			__fw_load_abort(buf);
+			break;
+		}
+	}
+	mutex_unlock(&fw_lock);
+	return 0;
+}
+EXPORT_SYMBOL(request_firmware_abort);
+
 #ifdef CONFIG_PM_SLEEP
 static ASYNC_DOMAIN_EXCLUSIVE(fw_cache_domain);
 
@@ -1324,18 +1364,6 @@ static int cache_firmware(const char *fw_name)
 	return ret;
 }
 
-static struct firmware_buf *fw_lookup_buf(const char *fw_name)
-{
-	struct firmware_buf *tmp;
-	struct firmware_cache *fwc = &fw_cache;
-
-	spin_lock(&fwc->lock);
-	tmp = __fw_lookup_buf(fw_name);
-	spin_unlock(&fwc->lock);
-
-	return tmp;
-}
-
 /**
  * uncache_firmware - remove one cached firmware image
  * @fw_name: the firmware image name
diff --git a/include/linux/firmware.h b/include/linux/firmware.h
index 5952933..ed90c8b 100644
--- a/include/linux/firmware.h
+++ b/include/linux/firmware.h
@@ -47,6 +47,7 @@ int request_firmware_nowait(
 	void (*cont)(const struct firmware *fw, void *context));
 
 void release_firmware(const struct firmware *fw);
+int request_firmware_abort(const char *fw_name);
 #else
 static inline int request_firmware(const struct firmware **fw,
 				   const char *name,
@@ -66,6 +67,9 @@ static inline void release_firmware(const struct firmware *fw)
 {
 }
 
+static inline int request_firmware_abort(const char *fw_name)
+{
+}
 #endif
 
 #ifdef CONFIG_FW_LOADER_USER_HELPER
-- 
1.7.9.5