firmware: Introduce request_firmware_direct()

firmware: Introduce request_firmware_direct()

When CONFIG_FW_LOADER_USER_HELPER is set, request_firmware() falls
back to the usermode helper for loading via udev when the direct
loading fails.  But the recent udev takes way too long timeout (60
seconds) for non-existing firmware.  This is unacceptable for the
drivers like microcode loader where they load firmwares optionally,
i.e. it's no error even if no requested file exists.

This patch provides a new helper function, request_firmware_direct().
It behaves as same as request_firmware() except for that it doesn't
fall back to usermode helper but returns an error immediately if the
f/w can't be loaded directly in kernel.

Without CONFIG_FW_LOADER_USER_HELPER=y, request_firmware_direct() is
just an alias of request_firmware(), due to obvious reason.

Tested-by: Prarit Bhargava <[email protected]>
Acked-by: Ming Lei <[email protected]>
Acked-by: Borislav Petkov <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>