V4L2_FLASH_STROBE_SOURCE_EXTERNAL
flash->strobe_source == V4L2_FLASH_STROBE_SOURCE_EXTERNAL)
V4L2_FLASH_STROBE_SOURCE_EXTERNAL);
external_strobe = (c->val == V4L2_FLASH_STROBE_SOURCE_EXTERNAL);
(1 << V4L2_FLASH_STROBE_SOURCE_EXTERNAL);
ctrl_cfg->max = V4L2_FLASH_STROBE_SOURCE_EXTERNAL;