120 lines
3.7 KiB
Plaintext
120 lines
3.7 KiB
Plaintext
/* $NetBSD: README.md_defs,v 1.6 2020/10/05 12:28:45 martin Exp $ */
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The following is trying to document the most important machine dependent
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defines used in the sysinst code.
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If HAVE_GPT is true, the MD code may limit the space used for the
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GPT at the beginning of the disk to allow e.g. a bootloader
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being added after it (see evbarm on allwinner SoCs, u-boot is
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copied at 8k into the image).
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/* Size limit for the initial GPT part, in bytes */
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#define MD_GPT_INITIAL_SIZE (8*1024)
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The default installation description is created as a static array using
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lots of conditionals. It may be overriden / replaced in the MD code
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(see below), an example for that is arch/i386/md.c when we have been
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booted from UEFI firmware.
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Name Value / example Description
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PART_BOOT (8*MEG) (undefined) if defined, a boot partition
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of this size (in bytes, rounded)
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will be part of the default partition
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suggestions. Must be compile time
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const! Use MD_PART_DEFAULTS if
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runtime adjustment is needed.
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PART_BOOT_MOUNT "/boot" (undefined) Add boot partition to fstab for
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this mount point
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PART_BOOT_TYPE FS_BSDFS Kind of filesystem used
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PART_BOOT_SUBT MBR_PTYPE_FAT12 File system specific sub type
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The boot partition is always inserted at the front of the suggested default
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partitions, to cope with firmwares that may not be able to load from the
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whole disk.
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If multiple boot partitions are required (see ofppc, where various schemes
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are supported, depending on exact model), the variables above can all be
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repeated with _BOOT1_ or _BOOT2_ name instead of _BOOT_.
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ATTENTION:
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PART_BOOT is in BYTE (not MB), while most other sizes
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(DEFROOTSIZE, DEFSWAP, ...) are in MB!
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The following macros provide optional MD hooks:
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MD_PART_DEFAULTS may be undefined
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used like:
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void MD_PART_DEFAULTS(struct pm_dev*, struct part_usage_info*,
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size_t num_usage_infos),
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Called before any of the partition usage defaults is ever used, can be used
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to adjust e.g. partition sizes to actual system requirements (align boot
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partition with cylindersize), or (since it is a macro and all params are
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by references) to completely swap the defaults (e.g. EFI vs. biosboot).
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If swapping, make sure allocation and num_usage_infos stays consistent,
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old allocation is done by calloc(3), use free(3) to release.
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MD_NEED_BOOTBLOCK may be undefined
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used like:
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bool MD_NEED_BOOTBLOCK(struct install_partition_desc *install)
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returns true if this setup needs boot blocks. Used for example on x86
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when UEFI installs do not need any bootblocks, but BIOS ones do.
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MD_MAY_SWAP_TO may be undefined
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used like:
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bool MD_MAY_SWAP_TO(const char *disk_name)
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returns true if the disk is usable as a swap device. Typical implementation
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in utils.c:may_swap_if_not_sdmmc.
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MD_SET_EXTRACT_FINALIZE may be undefined
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used like:
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int MD_SET_EXTRACT_FINALIZE(int update)
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extracts any additional parts of the distribution. Returns an error code
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if something fails.
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HAVE_PLAIN_DISKLABEL_BOOT may be undefined, only used on architectures
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that have MBR as primary with disklabel as
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secondary partitioning scheme (RAW_PART == 3)
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used like:
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bool HAVE_PLAIN_DISKLABEL_BOOT(const char *disk)
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returns true if the disk could be made bootable with only a disklabel
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(and no MBR).
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DISKLABEL_NO_ONDISK_VERIFY usually undefined
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If defined, do not verify the presence of on-disk disklabels before
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offering the disklabel partitioning scheme. This allows ports to use
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kernel translation for the disklabel ioctls (e.g. x68k uses Human68k
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partitions this way).
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HAVE_GPT_BOOT defined if the architecture can boot from GPT
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HAVE_EFI_BOOT defined if the architecture may be able
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to boot from an EFI partition
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NO_DISKLABEL_BOOT defined if the architecture can NOT boot
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from a disklabel partitioned disk
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