bootimage.bbclass, grub-efi.bbclass: Improve EFI & PCBIOS+EFI ISO support
Using the latest mkisofs it is possible to generate 3 different types
of ISO images, which can be used in various scenarios.
1) PCBIOS Only ISO
- This option remains unchanged by this commit
- Uses syslinux menus
- Can be directly copied with dd to a USB device
- Can be burned to optical media
2) EFI Only ISO
- Uses grub 2 menus
- Can be burned to optical media
- If you want to use this image on a USB device
extra steps must be taken in order to format the USB
device with fat32, and copy an EFI loader which will
in turn load the iso image
3) PCBIOS / EFI ISO
- This is a hybrid image ISO that will work for case 1 or 2
as above with the same restrictions and boot menu types
depending on what type of firmware is installed on
the hardware or depending on if EFI or "Legacy Boot" is
enabled on some UEFI firmwares.
The syslinux.bbclass is now always required because that is where the
isohybrid dependencies come from as well as the configuration data for
the isohybrid. The isohybrid is the secret sauce which allows the ISO
to work as optical media or as a disk image on USB or a HDD/SSD.
[YOCTO #4100]
Signed-off-by: Jason Wessel <jason.wessel@windriver.com> Signed-off-by: Saul Wold <sgw@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
