[RFC PATCH 07/13] driver core: firmware loader: introduce cache_firmware and uncache_firmware

[Ming Lei <ming.lei@canonical.com>]

This patches introduce two kernel APIs of cache_firmware and
uncache_firmware, both of which take the firmware file name
as the only parameter.

So any drivers can call cache_firmware to cache the specified
firmware file into kernel memory, and can use the cached firmware
in situations which can't request firmware from user space.

Signed-off-by: Ming Lei <ming.lei@canonical.com>
---
 drivers/base/firmware_class.c |   79 +++++++++++++++++++++++++++++++++++++++++
 include/linux/firmware.h      |   12 +++++++
 2 files changed, 91 insertions(+)

diff --git a/drivers/base/firmware_class.c b/drivers/base/firmware_class.c
index 225898e..674cb11 100644
--- a/drivers/base/firmware_class.c
+++ b/drivers/base/firmware_class.c
@@ -168,6 +168,22 @@ static int fw_lookup_and_alloate_buf(const char *fw_name,
 	return tmp ? 0 : -1;
 }
 
+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);
+	list_for_each_entry(tmp, &fwc->head, list)
+		if (!strcmp(tmp->fw_id, fw_name)) {
+			spin_unlock(&fwc->lock);
+			return tmp;
+		}
+	spin_unlock(&fwc->lock);
+
+	return NULL;
+}
+
 static void __fw_free_buf(struct kref *ref)
 {
 	struct firmware_buf *buf = to_fwbuf(ref);
@@ -833,6 +849,67 @@ request_firmware_nowait(
 	return 0;
 }
 
+/**
+ * cache_firmware - cache one firmware image in kernel memory space
+ * @fw_name: the firmware image name
+ *
+ * Cache firmware in kernel memory so that drivers can use the firmware
+ * when system isn't ready for drivers to request firmware image from
+ * userspace. Once returns successfully, driver can use request_firmware*
+ * to get the cached firmware without any interacting with user space
+ *
+ * Return 0 if the firmware image has been cached successfully
+ * Return !0 if it is not successfully
+ *
+ */
+int cache_firmware(const char *fw_name)
+{
+	int ret;
+	const struct firmware *fw;
+
+	pr_debug("%s: %s\n", __func__, fw_name);
+
+	ret = request_firmware(&fw, fw_name, NULL);
+
+	if (!ret)
+		kfree(fw);
+
+	pr_debug("%s: %s ret=%d\n", __func__, fw_name, ret);
+
+	return ret;
+}
+
+/**
+ * uncache_firmware - remove one cached firmware image
+ *
+ * @fw_name: the firmware image name
+ *
+ * Uncache one firmware image which has been cached successfully
+ * before.
+ *
+ * Return 0 if the firmware cache has been removed successfully
+ * Return !0 if it is not successfully
+ *
+ */
+int uncache_firmware(const char *fw_name)
+{
+	struct firmware_buf *buf;
+	struct firmware fw;
+
+	pr_debug("%s: %s\n", __func__, fw_name);
+
+	if (fw_get_builtin_firmware(&fw, fw_name))
+		return 0;
+
+	buf = fw_lookup_buf(fw_name);
+	if (buf) {
+		fw_free_buf(buf);
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
 static int __init firmware_class_init(void)
 {
 	fw_cache_init();
@@ -850,3 +927,5 @@ module_exit(firmware_class_exit);
 EXPORT_SYMBOL(release_firmware);
 EXPORT_SYMBOL(request_firmware);
 EXPORT_SYMBOL(request_firmware_nowait);
+EXPORT_SYMBOL_GPL(cache_firmware);
+EXPORT_SYMBOL_GPL(uncache_firmware);
diff --git a/include/linux/firmware.h b/include/linux/firmware.h
index e85b771..1bfa202 100644
--- a/include/linux/firmware.h
+++ b/include/linux/firmware.h
@@ -47,6 +47,8 @@ int request_firmware_nowait(
 	void (*cont)(const struct firmware *fw, void *context));
 
 void release_firmware(const struct firmware *fw);
+int cache_firmware(const char *name);
+int uncache_firmware(const char *name);
 #else
 static inline int request_firmware(const struct firmware **fw,
 				   const char *name,
@@ -65,6 +67,16 @@ static inline int request_firmware_nowait(
 static inline void release_firmware(const struct firmware *fw)
 {
 }
+
+int cache_firmware(const char *name)
+{
+	return -ENOENT;
+}
+
+int uncache_firmware(const char *name)
+{
+	return -EINVAL;
+}
 #endif
 
 #endif
-- 
1.7.9.5