driver-api/firmware/fallback-mechanisms.rst

97 important to re-iterate that no device is created if a direct filesystem lookup
113 -----------------------
114 .. kernel-doc:: drivers/base/firmware_loader/fallback.c
153 * ASYNC=whether or not the API request was asynchronous
171 in non-traditional paths -- paths outside of the listing documented in the
184 the uevent flag means you want to opt-in for the firmware fallback mechanism
196 The logic behind using MAX_JIFFY_OFFSET for non-uevents is that a custom
212 the peripheral's Linux device-driver needs to access this firmware.
222 .. kernel-doc:: include/linux/efi_embedded_fw.h
225 The EFI embedded-fw code works by scanning all EFI_BOOT_SERVICES_CODE memory
226 segments for an eight byte sequence matching prefix; if the prefix is found it
234 To register this array with the efi-embedded-fw code, a driver needs to:
243    drivers/firmware/efi/embedded-firmware.c wrapped in a #ifdef testing that
249 with the specified name directly from the disk, so the EFI embedded-fw can
254 1. The code scanning for EFI embedded-firmware runs near the end
258    embedded-firmware.
260 2. At the moment the EFI embedded-fw code assumes that firmwares always start at
264 3. At the moment the EFI embedded-fw code only works on x86 because other archs
265    free EFI_BOOT_SERVICES_CODE before the EFI embedded-fw code gets a chance to
268 4. The current brute-force scanning of EFI_BOOT_SERVICES_CODE is an ad-hoc
269    brute-force solution. There has been discussion to use the UEFI Platform
279 ------------------------------------------------------
288 3. Open the boot_services_code? files in a hex-editor, search for the
289    magic prefix for Silead firmware: F0 00 00 00 02 00 00 00, this gives you
292 4. The firmware has a specific pattern, it starts with a 8 byte page-address,
293    typically F0 00 00 00 02 00 00 00 for the first page followed by 32-bit
294    word-address + 32-bit value pairs. With the word-address incrementing 4
296    followed by a new page-address, followed by more word + value pairs. This
300 5. "dd if=boot_services_code? of=firmware bs=1 skip=<begin-addr> count=<len>"