// SPDX-License-Identifier: GPL-2.0-or-later
#pragma once

// Block devices that are found rather than assumed.
//
// The first four device numbers are fixed and always were: IDE 0 and 1, the
// ramdisk, the first USB stick. Everything since -- a SATA disk behind AHCI,
// an NVMe namespace, and every partition on any of them -- registers here at
// probe time and is handed the next free number from BLKDEV_FIRST.
//
// A partition is a block device in its own right, with block 0 at its first
// sector. That is the whole of partition support from a filesystem's side:
// SchFS on /dev/sata0p2 sees a volume that starts at zero, exactly as it would
// on a whole disk, and needs to know nothing about GPT -- which is also what
// a Linux driver for SchFS will see when it is handed /dev/sda2.

#define BLKDEV_FIRST   4
#define NBLKDEV       16        // so device numbers stay below SCHFS_DEV (64)

// The GPT partition type of a SchFS volume, as it is written and printed:
// 47138FA9-B79C-47A6-9F7D-AC1F7F572D5E. sgdisk and fdisk accept it as is.
// Generated for SchFS on 2026-10-22; nothing else uses it.
#define SCHFS_GPT_TYPE "47138FA9-B79C-47A6-9F7D-AC1F7F572D5E"

// What a driver supplies. `rw` moves `count` of the device's own sectors at
// `lba` to or from `buf`, a kernel address; it is never asked for more than
// BSIZE bytes at once. Returns 0, or -1 if the device refused.
struct blkdev_ops {
  int (*rw)(void *priv, uint64 lba, uint32 count, void *buf, int write);
  int (*flush)(void *priv);           // 0 when there is nothing to flush
};

// Register a whole disk. Its partition table, if it has one, is read here and
// every partition registered after it. Returns the disk's device number, or
// -1 if the table is full.
int  blkdev_register(const char *name, const struct blkdev_ops *ops,
                     void *priv, uint64 nsectors, uint32 secsize);

// The disk has gone -- a USB stick pulled out. Removes it and every partition
// on it, and drops whatever the buffer cache still holds for them, so that a
// different disk given the same number later is not served the old one's
// blocks. A filesystem still mounted from it fails on its next access.
void blkdev_unregister(int dev);
void binval(uint dev);                   // kernel/dev/bio.c
struct buf *bgetblk(uint dev, uint64 blockno);   // bread() without the read

int  blkdev_present(uint dev);
void blkdev_rw(struct buf *b);
int  blkdev_flush(uint dev);

// For the root probe: the registered devices in order, partitions after the
// disk they are on. Returns the device number of the i'th, or -1 past the end.
int         blkdev_nth(int i);
const char *blkdev_name(uint dev);
// 1 for a partition typed SCHFS_GPT_TYPE, 0 for anything that might be SchFS,
// and -1 for one whose type says it cannot be -- an EFI system partition, an
// MBR FAT type. The root probe takes 1 and then 0, so -1 is never tried: a
// FAT partition is mounted as FAT (kernel/fs/fat), not offered as a root.
int         blkdev_is_schfs(uint dev);

int  blkdev_info(char *buf, int cap);    // /proc/partitions

// Sectors straight to and from a filesystem's own buffer, for one that does
// not go through the buffer cache. kernel/fs/fat is: FAT addresses 512-byte
// sectors, a partition need not be a whole number of 4 KB blocks, and a
// cache block hanging over the end of one is a write into the next.
//
// `lba` counts the device's own sectors from the start of the partition, and
// the transfer is at most BSIZE bytes. Returns 0, or -1 for a transfer out of
// range or one the device refused -- it does not panic, because a USB stick
// can leave in the middle of one.
int  blkdev_xfer(uint dev, uint64 lba, uint32 count, void *buf, int write);
// Size in sectors and sector size; 0 if there is no such device.
uint64 blkdev_sectors(uint dev, uint32 *secsize);