firmware: add firmware_request_nowarn() - load firmware without warnings

Currently the firmware loader only exposes one silent path for querying
optional firmware, and that is firmware_request_direct(). This function
also disables the sysfs fallback mechanism, which might not always be the
desired behaviour [0].

This patch introduces a variations of request_firmware() that enable the
caller to disable the undesired warning messages but enables the sysfs
fallback mechanism. This is equivalent to adding FW_OPT_NO_WARN to the
old behaviour.

[0]: https://git.kernel.org/linus/c0cc00f250e1

Signed-off-by: Andres Rodriguez <andresx7@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Acked-by: Luis R. Rodriguez <mcgrof@kernel.org>
[mcgrof: used the old API calls as the full rename is not done yet, and
 add the caller for when FW_LOADER is disabled, enhance documentation ]
Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

3 files changed, 42 insertions, 0 deletions

diff --git a/Documentation/driver-api/firmware/request_firmware.rst b/Documentation/driver-api/firmware/request_firmware.rst
index d5ec95a7195b..f62bdcbfed5b 100644
--- a/Documentation/driver-api/firmware/request_firmware.rst
+++ b/Documentation/driver-api/firmware/request_firmware.rst
@@ -20,6 +20,11 @@ request_firmware
 .. kernel-doc:: drivers/base/firmware_loader/main.c
    :functions: request_firmware
 
+firmware_request_nowarn
+-----------------------
+.. kernel-doc:: drivers/base/firmware_loader/main.c
+   :functions: firmware_request_nowarn
+
 request_firmware_direct
 -----------------------
 .. kernel-doc:: drivers/base/firmware_loader/main.c
diff --git a/drivers/base/firmware_loader/main.c b/drivers/base/firmware_loader/main.c
index abdc4e4d55f1..0943e7065e0e 100644
--- a/drivers/base/firmware_loader/main.c
+++ b/drivers/base/firmware_loader/main.c
@@ -632,6 +632,33 @@ request_firmware(const struct firmware **firmware_p, const char *name,
 EXPORT_SYMBOL(request_firmware);
 
 /**
+ * firmware_request_nowarn() - request for an optional fw module
+ * @firmware: pointer to firmware image
+ * @name: name of firmware file
+ * @device: device for which firmware is being loaded
+ *
+ * This function is similar in behaviour to request_firmware(), except
+ * it doesn't produce warning messages when the file is not found.
+ * The sysfs fallback mechanism is enabled if direct filesystem lookup fails,
+ * however, however failures to find the firmware file with it are still
+ * suppressed. It is therefore up to the driver to check for the return value
+ * of this call and to decide when to inform the users of errors.
+ **/
+int firmware_request_nowarn(const struct firmware **firmware, const char *name,
+                            struct device *device)
+{
+        int ret;
+
+        /* Need to pin this module until return */
+        __module_get(THIS_MODULE);
+        ret = _request_firmware(firmware, name, device, NULL, 0,
+                                FW_OPT_UEVENT | FW_OPT_NO_WARN);
+        module_put(THIS_MODULE);
+        return ret;
+}
+EXPORT_SYMBOL_GPL(firmware_request_nowarn);
+
+/**
  * request_firmware_direct() - load firmware directly without usermode helper
  * @firmware_p: pointer to firmware image
  * @name: name of firmware file
diff --git a/include/linux/firmware.h b/include/linux/firmware.h
index 41050417cafb..2dd566c91d44 100644
--- a/include/linux/firmware.h
+++ b/include/linux/firmware.h
@@ -42,6 +42,8 @@ struct builtin_fw {
 #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);
+int firmware_request_nowarn(const struct firmware **fw, const char *name,
+                            struct device *device);
 int request_firmware_nowait(
         struct module *module, bool uevent,
         const char *name, struct device *device, gfp_t gfp, void *context,
@@ -59,6 +61,14 @@ static inline int request_firmware(const struct firmware **fw,
 {
         return -EINVAL;
 }
+
+static inline int firmware_request_nowarn(const struct firmware **fw,
+                                          const char *name,
+                                          struct device *device)
+{
+        return -EINVAL;
+}
+
 static inline int request_firmware_nowait(
         struct module *module, bool uevent,
         const char *name, struct device *device, gfp_t gfp, void *context,