Firmware lookup order¶
Different functionality is available to enable firmware to be found. Below is chronological order of how firmware will be looked for once a driver issues a firmware API call.
- The ‘’Built-in firmware’’ is checked first, if the firmware is present we return it immediately
- The ‘’Firmware cache’’ is looked at next. If the firmware is found we return it immediately
- The ‘’Direct filesystem lookup’’ is performed next, if found we return it immediately
- The ‘’Platform firmware fallback’’ is performed next, but only when
firmware_request_platform()is used, if found we return it immediately
- If no firmware has been found and the fallback mechanism was enabled the sysfs interface is created. After this either a kobject uevent is issued or the custom firmware loading is relied upon for firmware loading up to the timeout value.