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README.md_defs revision 1.4 
      1 /* $NetBSD: README.md_defs,v 1.4 2020/01/20 21:26:35 martin Exp $ */
      2 
      3 The following is trying to document the most important machine dependent
      4 defines used in the sysinst code.
      5 
      6 
      7 If HAVE_GPT is true, the MD code may limit the space used for the
      8 GPT at the beginning of the disk to allow e.g. a bootloader
      9 being added after it (see evbarm on allwinner SoCs, u-boot is
     10 copied at 8k into the image).
     11 
     12 /* Size limit for the initial GPT part, in bytes */
     13 #define	MD_GPT_INITIAL_SIZE		(8*1024)
     14 
     15 
     16 The default installation description is created as a static array using
     17 lots of conditionals. It may be overriden / replaced in the MD code
     18 (see below), an example for that is arch/i386/md.c when we have been
     19 booted from UEFI firmware.
     20 
     21 Name		Value / example		Description
     22 PART_BOOT	(8*MEG) (undefined)	if defined, a boot partition
     23 					of this size (in bytes, rounded)
     24 					will be part of the default partition
     25 					suggestions. Must be compile time
     26 					const! Use MD_PART_DEFAULTS if
     27 					runtime adjustment is needed.
     28 PART_BOOT_MOUNT	"/boot" (undefined)	Add boot partition to fstab for
     29 					this mount point
     30 PART_BOOT_TYPE	FS_BSDFS		Kind of filesystem used
     31 PART_BOOT_SUBT	MBR_PTYPE_FAT12		File system specific sub type
     32 
     33 
     34 The boot partition is always inserted at the front of the suggested default
     35 partitions, to cope with firmwares that may not be able to load from the
     36 whole disk.
     37 
     38 If multiple boot partitions are required (see ofppc, where various schemes
     39 are supported, depending on exact model), the variables above can all be
     40 repeated with _BOOT1_ or _BOOT2_ name instead of _BOOT_.
     41 
     42 
     43 ATTENTION:
     44 	PART_BOOT	is in BYTE (not MB), while most other sizes
     45 			(DEFROOTSIZE, DEFSWAP, ...) are in MB!
     46 
     47 
     48 The following macros provide optional MD hooks:
     49 
     50 MD_PART_DEFAULTS	may be undefined
     51 
     52 used like:
     53 
     54 	void MD_PART_DEFAULTS(struct pm_dev*, struct part_usage_info*,
     55 	    size_t num_usage_infos),
     56 
     57 Called before any of the partition usage defaults is ever used, can be used
     58 to adjust e.g. partition sizes to actual system requirements (align boot
     59 partition with cylindersize), or (since it is a macro and all params are
     60 by references) to completely swap the defaults (e.g. EFI vs. biosboot).
     61 If swapping, make sure allocation and num_usage_infos stays consistent,
     62 old allocation is done by calloc(3), use free(3) to release.
     63 
     64 
     65 MD_NEED_BOOTBLOCK	may be undefined
     66 
     67 used like:
     68 
     69 	bool MD_NEED_BOOTBLOCK(struct install_partition_desc *install)
     70 
     71 returns true if this setup needs boot blocks. Used for example on x86
     72 when UEFI installs do not need any bootblocks, but BIOS ones do.
     73 
     74 MD_MAY_SWAP_TO		may be undefined
     75 
     76 used  like:
     77 
     78 	bool MD_MAY_SWAP_TO(const char *disk_name)
     79 
     80 returns true if the disk is usable as a swap device. Typical implementation
     81 in utils.c:may_swap_if_not_sdmmc.
     82 
     83 MD_SET_EXTRACT_FINALIZE	may be undefined
     84 
     85 used like:
     86 
     87 	int MD_SET_EXTRACT_FINALIZE(int update)
     88 
     89 extracts any additional parts of the distribution. Returns an error code
     90 if something fails.
     91 
     92 
     93 HAVE_PLAIN_DISKLABEL_BOOT	may be undefined, only used on architectures
     94 				that have MBR as primary with disklabel as
     95 				secondary partitioning scheme (RAW_PART != 2)
     96 
     97 used like:
     98 
     99 	bool HAVE_PLAIN_DISKLABEL_BOOT(const char *disk)
    100 
    101 returns true if the disk could be made bootable with only a disklabel
    102 (and no MBR).
    103 
    104 
    105 DISKLABEL_NO_ONDISK_VERIFY	usually undefined
    106 
    107 If defined, do not verify the presence of on-disk disklabels before
    108 offering the disklabel partitioning scheme. This allows ports to use
    109 kernel translation for the disklabel ioctls (e.g. x68k uses Human68k
    110 partitions this way).
    111 
    112 
    113 HAVE_GPT_BOOT			defined if the architecture can boot from GPT
    114 
    115 NO_DISKLABEL_BOOT		defined if the architecture can NOT boot
    116 				from a disklabel partitioned disk
    117