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[v6,04/13] firmware_loader: document firmware_sysfs_fallback()

Message ID 20180508181247.19431-5-mcgrof@kernel.org
State New, archived
Headers show

Commit Message

Luis Chamberlain May 8, 2018, 6:12 p.m. UTC
This also sets the expecations for future fallback interfaces, even
if they are not exported.

Signed-off-by: Luis R. Rodriguez <mcgrof@kernel.org>
 drivers/base/firmware_loader/fallback.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)
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diff --git a/drivers/base/firmware_loader/fallback.c b/drivers/base/firmware_loader/fallback.c
index 3db9e0f225ac..9169e7b9800c 100644
--- a/drivers/base/firmware_loader/fallback.c
+++ b/drivers/base/firmware_loader/fallback.c
@@ -662,6 +662,26 @@  static bool fw_run_sysfs_fallback(enum fw_opt opt_flags)
 	return fw_force_sysfs_fallback(opt_flags);
+ * firmware_fallback_sysfs() - use the fallback mechanism to find firmware
+ * @fw: pointer to firmware image
+ * @name: name of firmware file to look for
+ * @device: device for which firmware is being loaded
+ * @opt_flags: options to control firmware loading behaviour
+ * @ret: return value from direct lookup which triggered the fallback mechanism
+ *
+ * This function is called if direct lookup for the firmware failed, it enables
+ * a fallback mechanism through userspace by exposing a sysfs loading
+ * interface. Userspace is in charge of loading the firmware through the syfs
+ * loading interface. This syfs fallback mechanism may be disabled completely
+ * on a system by setting the proc sysctl value ignore_sysfs_fallback to true.
+ * If this false we check if the internal API caller set the @FW_OPT_NOFALLBACK
+ * flag, if so it would also disable the fallback mechanism. A system may want
+ * to enfoce the sysfs fallback mechanism at all times, it can do this by
+ * setting ignore_sysfs_fallback to false and force_sysfs_fallback to true.
+ * Enabling force_sysfs_fallback is functionally equivalent to build a kernel
+ **/
 int firmware_fallback_sysfs(struct firmware *fw, const char *name,
 			    struct device *device,
 			    enum fw_opt opt_flags,