firmware_loader: formalize built-in firmware API

Formalize the built-in firmware with a proper API. This can later
be used by other callers where all they need is built-in firmware.

We export the firmware_request_builtin() call for now only
under the TEST_FIRMWARE symbol namespace as there are no
direct modular users for it. If they pop up they are free
to export it generally. Built-in code always gets access to
the callers and we'll demonstrate a hidden user which has been
lurking in the kernel for a while and the reason why using a
proper API was better long term.

Reviewed-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
Link: https://lore.kernel.org/r/20211021155843.1969401-2-mcgrof@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/include/linux/firmware.h b/include/linux/firmware.h
index 25109192cebe..d743a8d1c2fe 100644
--- a/include/linux/firmware.h
+++ b/include/linux/firmware.h
@@ -20,12 +20,19 @@ struct firmware {
 struct module;
 struct device;
 
+/*
+ * Built-in firmware functionality is only available if FW_LOADER=y, but not
+ * FW_LOADER=m
+ */
+#ifdef CONFIG_FW_LOADER
 struct builtin_fw {
 	char *name;
 	void *data;
 	unsigned long size;
 };
 
+bool firmware_request_builtin(struct firmware *fw, const char *name);
+
 /* We have to play tricks here much like stringify() to get the
    __COUNTER__ macro to be expanded as we want it */
 #define __fw_concat1(x, y) x##y
@@ -38,6 +45,14 @@ struct builtin_fw {
 	static const struct builtin_fw __fw_concat(__builtin_fw,__COUNTER__) \
 	__used __section(".builtin_fw") = { name, blob, size }
 
+#else
+static inline bool firmware_request_builtin(struct firmware *fw,
+					    const char *name)
+{
+	return false;
+}
+#endif
+
 #if defined(CONFIG_FW_LOADER) || (defined(CONFIG_FW_LOADER_MODULE) && defined(MODULE))
 int request_firmware(const struct firmware **fw, const char *name,
 		     struct device *device);