linux/drivers/base/firmware_loader/fallback.c

// SPDX-License-Identifier: GPL-2.0

#include <linux/types.h>
#include <linux/kconfig.h>
#include <linux/list.h>
#include <linux/security.h>
#include <linux/umh.h>
#include <linux/sysctl.h>
#include <linux/module.h>

#include "fallback.h"
#include "firmware.h"

/*
 * firmware fallback mechanism
 */

/*
 * use small loading timeout for caching devices' firmware because all these
 * firmware images have been loaded successfully at lease once, also system is
 * ready for completing firmware loading now. The maximum size of firmware in
 * current distributions is about 2M bytes, so 10 secs should be enough.
 */
void fw_fallback_set_cache_timeout(void)
{ … }

/* Restores the timeout to the value last configured during normal operation */
void fw_fallback_set_default_timeout(void)
{ … }

static long firmware_loading_timeout(void)
{ … }

static inline int fw_sysfs_wait_timeout(struct fw_priv *fw_priv,  long timeout)
{ … }

static LIST_HEAD(pending_fw_head);

void kill_pending_fw_fallback_reqs(bool kill_all)
{ … }

/**
 * fw_load_sysfs_fallback() - load a firmware via the sysfs fallback mechanism
 * @fw_sysfs: firmware sysfs information for the firmware to load
 * @timeout: timeout to wait for the load
 *
 * In charge of constructing a sysfs fallback interface for firmware loading.
 **/
static int fw_load_sysfs_fallback(struct fw_sysfs *fw_sysfs, long timeout)
{ … }

static int fw_load_from_user_helper(struct firmware *firmware,
				    const char *name, struct device *device,
				    u32 opt_flags)
{ … }

static bool fw_force_sysfs_fallback(u32 opt_flags)
{ … }

static bool fw_run_sysfs_fallback(u32 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, as defined by
 *	       &enum fw_opt
 * @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 sysfs
 * loading interface. This sysfs fallback mechanism may be disabled completely
 * on a system by setting the proc sysctl value ignore_sysfs_fallback to true.
 * If this is false we check if the internal API caller set the
 * @FW_OPT_NOFALLBACK_SYSFS flag, if so it would also disable the fallback
 * mechanism. A system may want to enforce 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
 * with CONFIG_FW_LOADER_USER_HELPER_FALLBACK.
 **/
int firmware_fallback_sysfs(struct firmware *fw, const char *name,
			    struct device *device,
			    u32 opt_flags,
			    int ret)
{ … }