u-boot/include/blk.h
Simon Glass 87571b7f20 dm: blk: Add a function to return the device type
Use the uclass name to get the device type for a block device.

Signed-off-by: Simon Glass <sjg@chromium.org>
2022-04-25 10:00:03 -04:00

812 lines
25 KiB
C

/* SPDX-License-Identifier: GPL-2.0+ */
/*
* (C) Copyright 2000-2004
* Wolfgang Denk, DENX Software Engineering, wd@denx.de.
*/
#ifndef BLK_H
#define BLK_H
#include <efi.h>
#ifdef CONFIG_SYS_64BIT_LBA
typedef uint64_t lbaint_t;
#define LBAFlength "ll"
#else
typedef ulong lbaint_t;
#define LBAFlength "l"
#endif
#define LBAF "%" LBAFlength "x"
#define LBAFU "%" LBAFlength "u"
struct udevice;
/* Interface types: */
enum if_type {
IF_TYPE_UNKNOWN = 0,
IF_TYPE_IDE,
IF_TYPE_SCSI,
IF_TYPE_ATAPI,
IF_TYPE_USB,
IF_TYPE_DOC,
IF_TYPE_MMC,
IF_TYPE_SD,
IF_TYPE_SATA,
IF_TYPE_HOST,
IF_TYPE_NVME,
IF_TYPE_EFI_LOADER,
IF_TYPE_PVBLOCK,
IF_TYPE_VIRTIO,
IF_TYPE_EFI_MEDIA,
IF_TYPE_COUNT, /* Number of interface types */
};
#define BLK_VEN_SIZE 40
#define BLK_PRD_SIZE 20
#define BLK_REV_SIZE 8
#define PART_FORMAT_PCAT 0x1
#define PART_FORMAT_GPT 0x2
/*
* Identifies the partition table type (ie. MBR vs GPT GUID) signature
*/
enum sig_type {
SIG_TYPE_NONE,
SIG_TYPE_MBR,
SIG_TYPE_GUID,
SIG_TYPE_COUNT /* Number of signature types */
};
/*
* With driver model (CONFIG_BLK) this is uclass platform data, accessible
* with dev_get_uclass_plat(dev)
*/
struct blk_desc {
/*
* TODO: With driver model we should be able to use the parent
* device's uclass instead.
*/
enum if_type if_type; /* type of the interface */
int devnum; /* device number */
unsigned char part_type; /* partition type */
unsigned char target; /* target SCSI ID */
unsigned char lun; /* target LUN */
unsigned char hwpart; /* HW partition, e.g. for eMMC */
unsigned char type; /* device type */
unsigned char removable; /* removable device */
#ifdef CONFIG_LBA48
/* device can use 48bit addr (ATA/ATAPI v7) */
unsigned char lba48;
#endif
lbaint_t lba; /* number of blocks */
unsigned long blksz; /* block size */
int log2blksz; /* for convenience: log2(blksz) */
char vendor[BLK_VEN_SIZE + 1]; /* device vendor string */
char product[BLK_PRD_SIZE + 1]; /* device product number */
char revision[BLK_REV_SIZE + 1]; /* firmware revision */
enum sig_type sig_type; /* Partition table signature type */
union {
uint32_t mbr_sig; /* MBR integer signature */
efi_guid_t guid_sig; /* GPT GUID Signature */
};
#if CONFIG_IS_ENABLED(BLK)
/*
* For now we have a few functions which take struct blk_desc as a
* parameter. This field allows them to look up the associated
* device. Once these functions are removed we can drop this field.
*/
struct udevice *bdev;
#else
unsigned long (*block_read)(struct blk_desc *block_dev,
lbaint_t start,
lbaint_t blkcnt,
void *buffer);
unsigned long (*block_write)(struct blk_desc *block_dev,
lbaint_t start,
lbaint_t blkcnt,
const void *buffer);
unsigned long (*block_erase)(struct blk_desc *block_dev,
lbaint_t start,
lbaint_t blkcnt);
void *priv; /* driver private struct pointer */
#endif
};
#define BLOCK_CNT(size, blk_desc) (PAD_COUNT(size, blk_desc->blksz))
#define PAD_TO_BLOCKSIZE(size, blk_desc) \
(PAD_SIZE(size, blk_desc->blksz))
#if CONFIG_IS_ENABLED(BLOCK_CACHE)
/**
* blkcache_init() - initialize the block cache list pointers
*/
int blkcache_init(void);
/**
* blkcache_read() - attempt to read a set of blocks from cache
*
* @param iftype - IF_TYPE_x for type of device
* @param dev - device index of particular type
* @param start - starting block number
* @param blkcnt - number of blocks to read
* @param blksz - size in bytes of each block
* @param buf - buffer to contain cached data
*
* Return: - 1 if block returned from cache, 0 otherwise.
*/
int blkcache_read(int iftype, int dev,
lbaint_t start, lbaint_t blkcnt,
unsigned long blksz, void *buffer);
/**
* blkcache_fill() - make data read from a block device available
* to the block cache
*
* @param iftype - IF_TYPE_x for type of device
* @param dev - device index of particular type
* @param start - starting block number
* @param blkcnt - number of blocks available
* @param blksz - size in bytes of each block
* @param buf - buffer containing data to cache
*
*/
void blkcache_fill(int iftype, int dev,
lbaint_t start, lbaint_t blkcnt,
unsigned long blksz, void const *buffer);
/**
* blkcache_invalidate() - discard the cache for a set of blocks
* because of a write or device (re)initialization.
*
* @param iftype - IF_TYPE_x for type of device
* @param dev - device index of particular type
*/
void blkcache_invalidate(int iftype, int dev);
/**
* blkcache_configure() - configure block cache
*
* @param blocks - maximum blocks per entry
* @param entries - maximum entries in cache
*/
void blkcache_configure(unsigned blocks, unsigned entries);
/*
* statistics of the block cache
*/
struct block_cache_stats {
unsigned hits;
unsigned misses;
unsigned entries; /* current entry count */
unsigned max_blocks_per_entry;
unsigned max_entries;
};
/**
* get_blkcache_stats() - return statistics and reset
*
* @param stats - statistics are copied here
*/
void blkcache_stats(struct block_cache_stats *stats);
#else
static inline int blkcache_read(int iftype, int dev,
lbaint_t start, lbaint_t blkcnt,
unsigned long blksz, void *buffer)
{
return 0;
}
static inline void blkcache_fill(int iftype, int dev,
lbaint_t start, lbaint_t blkcnt,
unsigned long blksz, void const *buffer) {}
static inline void blkcache_invalidate(int iftype, int dev) {}
#endif
#if CONFIG_IS_ENABLED(BLK)
struct udevice;
/* Operations on block devices */
struct blk_ops {
/**
* read() - read from a block device
*
* @dev: Device to read from
* @start: Start block number to read (0=first)
* @blkcnt: Number of blocks to read
* @buffer: Destination buffer for data read
* @return number of blocks read, or -ve error number (see the
* IS_ERR_VALUE() macro
*/
unsigned long (*read)(struct udevice *dev, lbaint_t start,
lbaint_t blkcnt, void *buffer);
/**
* write() - write to a block device
*
* @dev: Device to write to
* @start: Start block number to write (0=first)
* @blkcnt: Number of blocks to write
* @buffer: Source buffer for data to write
* @return number of blocks written, or -ve error number (see the
* IS_ERR_VALUE() macro
*/
unsigned long (*write)(struct udevice *dev, lbaint_t start,
lbaint_t blkcnt, const void *buffer);
/**
* erase() - erase a section of a block device
*
* @dev: Device to (partially) erase
* @start: Start block number to erase (0=first)
* @blkcnt: Number of blocks to erase
* @return number of blocks erased, or -ve error number (see the
* IS_ERR_VALUE() macro
*/
unsigned long (*erase)(struct udevice *dev, lbaint_t start,
lbaint_t blkcnt);
/**
* select_hwpart() - select a particular hardware partition
*
* Some devices (e.g. MMC) can support partitioning at the hardware
* level. This is quite separate from the normal idea of
* software-based partitions. MMC hardware partitions must be
* explicitly selected. Once selected only the region of the device
* covered by that partition is accessible.
*
* The MMC standard provides for two boot partitions (numbered 1 and 2),
* rpmb (3), and up to 4 addition general-purpose partitions (4-7).
*
* @desc: Block device to update
* @hwpart: Hardware partition number to select. 0 means the raw
* device, 1 is the first partition, 2 is the second, etc.
* @return 0 if OK, -ve on error
*/
int (*select_hwpart)(struct udevice *dev, int hwpart);
};
#define blk_get_ops(dev) ((struct blk_ops *)(dev)->driver->ops)
/*
* These functions should take struct udevice instead of struct blk_desc,
* but this is convenient for migration to driver model. Add a 'd' prefix
* to the function operations, so that blk_read(), etc. can be reserved for
* functions with the correct arguments.
*/
unsigned long blk_dread(struct blk_desc *block_dev, lbaint_t start,
lbaint_t blkcnt, void *buffer);
unsigned long blk_dwrite(struct blk_desc *block_dev, lbaint_t start,
lbaint_t blkcnt, const void *buffer);
unsigned long blk_derase(struct blk_desc *block_dev, lbaint_t start,
lbaint_t blkcnt);
/**
* blk_find_device() - Find a block device
*
* This function does not activate the device. The device will be returned
* whether or not it is activated.
*
* @if_type: Interface type (enum if_type_t)
* @devnum: Device number (specific to each interface type)
* @devp: the device, if found
* Return: 0 if found, -ENODEV if no device found, or other -ve error value
*/
int blk_find_device(int if_type, int devnum, struct udevice **devp);
/**
* blk_get_device() - Find and probe a block device ready for use
*
* @if_type: Interface type (enum if_type_t)
* @devnum: Device number (specific to each interface type)
* @devp: the device, if found
* Return: 0 if found, -ENODEV if no device found, or other -ve error value
*/
int blk_get_device(int if_type, int devnum, struct udevice **devp);
/**
* blk_first_device() - Find the first device for a given interface
*
* The device is probed ready for use
*
* @devnum: Device number (specific to each interface type)
* @devp: the device, if found
* Return: 0 if found, -ENODEV if no device, or other -ve error value
*/
int blk_first_device(int if_type, struct udevice **devp);
/**
* blk_next_device() - Find the next device for a given interface
*
* This can be called repeatedly after blk_first_device() to iterate through
* all devices of the given interface type.
*
* The device is probed ready for use
*
* @devp: On entry, the previous device returned. On exit, the next
* device, if found
* Return: 0 if found, -ENODEV if no device, or other -ve error value
*/
int blk_next_device(struct udevice **devp);
/**
* blk_create_device() - Create a new block device
*
* @parent: Parent of the new device
* @drv_name: Driver name to use for the block device
* @name: Name for the device
* @if_type: Interface type (enum if_type_t)
* @devnum: Device number, specific to the interface type, or -1 to
* allocate the next available number
* @blksz: Block size of the device in bytes (typically 512)
* @lba: Total number of blocks of the device
* @devp: the new device (which has not been probed)
*/
int blk_create_device(struct udevice *parent, const char *drv_name,
const char *name, int if_type, int devnum, int blksz,
lbaint_t lba, struct udevice **devp);
/**
* blk_create_devicef() - Create a new named block device
*
* @parent: Parent of the new device
* @drv_name: Driver name to use for the block device
* @name: Name for the device (parent name is prepended)
* @if_type: Interface type (enum if_type_t)
* @devnum: Device number, specific to the interface type, or -1 to
* allocate the next available number
* @blksz: Block size of the device in bytes (typically 512)
* @lba: Total number of blocks of the device
* @devp: the new device (which has not been probed)
*/
int blk_create_devicef(struct udevice *parent, const char *drv_name,
const char *name, int if_type, int devnum, int blksz,
lbaint_t lba, struct udevice **devp);
/**
* blk_probe_or_unbind() - Try to probe
*
* Try to probe the device, primarily for enumerating partitions.
* If it fails, the device itself is unbound since it means that it won't
* work any more.
*
* @dev: The device to probe
* Return: 0 if OK, -ve on error
*/
int blk_probe_or_unbind(struct udevice *dev);
/**
* blk_unbind_all() - Unbind all device of the given interface type
*
* The devices are removed and then unbound.
*
* @if_type: Interface type to unbind
* Return: 0 if OK, -ve on error
*/
int blk_unbind_all(int if_type);
/**
* blk_find_max_devnum() - find the maximum device number for an interface type
*
* Finds the last allocated device number for an interface type @if_type. The
* next number is safe to use for a newly allocated device.
*
* @if_type: Interface type to scan
* Return: maximum device number found, or -ENODEV if none, or other -ve on
* error
*/
int blk_find_max_devnum(enum if_type if_type);
/**
* blk_next_free_devnum() - get the next device number for an interface type
*
* Finds the next number that is safe to use for a newly allocated device for
* an interface type @if_type.
*
* @if_type: Interface type to scan
* Return: next device number safe to use, or -ve on error
*/
int blk_next_free_devnum(enum if_type if_type);
/**
* blk_select_hwpart() - select a hardware partition
*
* Select a hardware partition if the device supports it (typically MMC does)
*
* @dev: Device to update
* @hwpart: Partition number to select
* Return: 0 if OK, -ve on error
*/
int blk_select_hwpart(struct udevice *dev, int hwpart);
/**
* blk_get_from_parent() - obtain a block device by looking up its parent
*
* All devices with
*/
int blk_get_from_parent(struct udevice *parent, struct udevice **devp);
/**
* blk_get_devtype() - Get the device type of a block device
*
* @dev: Block device to check
* Return: device tree, i.e. the uclass name of its parent, e.g. "mmc"
*/
const char *blk_get_devtype(struct udevice *dev);
/**
* blk_get_by_device() - Get the block device descriptor for the given device
* @dev: Instance of a storage device
*
* Return: With block device descriptor on success , NULL if there is no such
* block device.
*/
struct blk_desc *blk_get_by_device(struct udevice *dev);
#else
#include <errno.h>
/*
* These functions should take struct udevice instead of struct blk_desc,
* but this is convenient for migration to driver model. Add a 'd' prefix
* to the function operations, so that blk_read(), etc. can be reserved for
* functions with the correct arguments.
*/
static inline ulong blk_dread(struct blk_desc *block_dev, lbaint_t start,
lbaint_t blkcnt, void *buffer)
{
ulong blks_read;
if (blkcache_read(block_dev->if_type, block_dev->devnum,
start, blkcnt, block_dev->blksz, buffer))
return blkcnt;
/*
* We could check if block_read is NULL and return -ENOSYS. But this
* bloats the code slightly (cause some board to fail to build), and
* it would be an error to try an operation that does not exist.
*/
blks_read = block_dev->block_read(block_dev, start, blkcnt, buffer);
if (blks_read == blkcnt)
blkcache_fill(block_dev->if_type, block_dev->devnum,
start, blkcnt, block_dev->blksz, buffer);
return blks_read;
}
static inline ulong blk_dwrite(struct blk_desc *block_dev, lbaint_t start,
lbaint_t blkcnt, const void *buffer)
{
blkcache_invalidate(block_dev->if_type, block_dev->devnum);
return block_dev->block_write(block_dev, start, blkcnt, buffer);
}
static inline ulong blk_derase(struct blk_desc *block_dev, lbaint_t start,
lbaint_t blkcnt)
{
blkcache_invalidate(block_dev->if_type, block_dev->devnum);
return block_dev->block_erase(block_dev, start, blkcnt);
}
/**
* struct blk_driver - Driver for block interface types
*
* This provides access to the block devices for each interface type. One
* driver should be provided using U_BOOT_LEGACY_BLK() for each interface
* type that is to be supported.
*
* @if_typename: Interface type name
* @if_type: Interface type
* @max_devs: Maximum number of devices supported
* @desc: Pointer to list of devices for this interface type,
* or NULL to use @get_dev() instead
*/
struct blk_driver {
const char *if_typename;
enum if_type if_type;
int max_devs;
struct blk_desc *desc;
/**
* get_dev() - get a pointer to a block device given its number
*
* Each interface allocates its own devices and typically
* struct blk_desc is contained with the interface's data structure.
* There is no global numbering for block devices. This method allows
* the device for an interface type to be obtained when @desc is NULL.
*
* @devnum: Device number (0 for first device on that interface,
* 1 for second, etc.
* @descp: Returns pointer to the block device on success
* @return 0 if OK, -ve on error
*/
int (*get_dev)(int devnum, struct blk_desc **descp);
/**
* select_hwpart() - Select a hardware partition
*
* Some devices (e.g. MMC) can support partitioning at the hardware
* level. This is quite separate from the normal idea of
* software-based partitions. MMC hardware partitions must be
* explicitly selected. Once selected only the region of the device
* covered by that partition is accessible.
*
* The MMC standard provides for two boot partitions (numbered 1 and 2),
* rpmb (3), and up to 4 addition general-purpose partitions (4-7).
* Partition 0 is the main user-data partition.
*
* @desc: Block device descriptor
* @hwpart: Hardware partition number to select. 0 means the main
* user-data partition, 1 is the first partition, 2 is
* the second, etc.
* @return 0 if OK, other value for an error
*/
int (*select_hwpart)(struct blk_desc *desc, int hwpart);
};
/*
* Declare a new U-Boot legacy block driver. New drivers should use driver
* model (UCLASS_BLK).
*/
#define U_BOOT_LEGACY_BLK(__name) \
ll_entry_declare(struct blk_driver, __name, blk_driver)
struct blk_driver *blk_driver_lookup_type(int if_type);
#endif /* !CONFIG_BLK */
/**
* blk_get_devnum_by_typename() - Get a block device by type and number
*
* This looks through the available block devices of the given type, returning
* the one with the given @devnum.
*
* @if_type: Block device type
* @devnum: Device number
* Return: point to block device descriptor, or NULL if not found
*/
struct blk_desc *blk_get_devnum_by_type(enum if_type if_type, int devnum);
/**
* blk_get_devnum_by_type() - Get a block device by type name, and number
*
* This looks up the block device type based on @if_typename, then calls
* blk_get_devnum_by_type().
*
* @if_typename: Block device type name
* @devnum: Device number
* Return: point to block device descriptor, or NULL if not found
*/
struct blk_desc *blk_get_devnum_by_typename(const char *if_typename,
int devnum);
/**
* blk_dselect_hwpart() - select a hardware partition
*
* This selects a hardware partition (such as is supported by MMC). The block
* device size may change as this effectively points the block device to a
* partition at the hardware level. See the select_hwpart() method above.
*
* @desc: Block device descriptor for the device to select
* @hwpart: Partition number to select
* Return: 0 if OK, -ve on error
*/
int blk_dselect_hwpart(struct blk_desc *desc, int hwpart);
/**
* blk_list_part() - list the partitions for block devices of a given type
*
* This looks up the partition type for each block device of type @if_type,
* then displays a list of partitions.
*
* @if_type: Block device type
* Return: 0 if OK, -ENODEV if there is none of that type
*/
int blk_list_part(enum if_type if_type);
/**
* blk_list_devices() - list the block devices of a given type
*
* This lists each block device of the type @if_type, showing the capacity
* as well as type-specific information.
*
* @if_type: Block device type
*/
void blk_list_devices(enum if_type if_type);
/**
* blk_show_device() - show information about a given block device
*
* This shows the block device capacity as well as type-specific information.
*
* @if_type: Block device type
* @devnum: Device number
* Return: 0 if OK, -ENODEV for invalid device number
*/
int blk_show_device(enum if_type if_type, int devnum);
/**
* blk_print_device_num() - show information about a given block device
*
* This is similar to blk_show_device() but returns an error if the block
* device type is unknown.
*
* @if_type: Block device type
* @devnum: Device number
* Return: 0 if OK, -ENODEV for invalid device number, -ENOENT if the block
* device is not connected
*/
int blk_print_device_num(enum if_type if_type, int devnum);
/**
* blk_print_part_devnum() - print the partition information for a device
*
* @if_type: Block device type
* @devnum: Device number
* Return: 0 if OK, -ENOENT if the block device is not connected, -ENOSYS if
* the interface type is not supported, other -ve on other error
*/
int blk_print_part_devnum(enum if_type if_type, int devnum);
/**
* blk_read_devnum() - read blocks from a device
*
* @if_type: Block device type
* @devnum: Device number
* @blkcnt: Number of blocks to read
* @buffer: Address to write data to
* Return: number of blocks read, or -ve error number on error
*/
ulong blk_read_devnum(enum if_type if_type, int devnum, lbaint_t start,
lbaint_t blkcnt, void *buffer);
/**
* blk_write_devnum() - write blocks to a device
*
* @if_type: Block device type
* @devnum: Device number
* @blkcnt: Number of blocks to write
* @buffer: Address to read data from
* Return: number of blocks written, or -ve error number on error
*/
ulong blk_write_devnum(enum if_type if_type, int devnum, lbaint_t start,
lbaint_t blkcnt, const void *buffer);
/**
* blk_select_hwpart_devnum() - select a hardware partition
*
* This is similar to blk_dselect_hwpart() but it looks up the interface and
* device number.
*
* @if_type: Block device type
* @devnum: Device number
* @hwpart: Partition number to select
* Return: 0 if OK, -ve on error
*/
int blk_select_hwpart_devnum(enum if_type if_type, int devnum, int hwpart);
/**
* blk_get_if_type_name() - Get the name of an interface type
*
* @if_type: Interface type to check
* Return: name of interface, or NULL if none
*/
const char *blk_get_if_type_name(enum if_type if_type);
/**
* blk_common_cmd() - handle common commands with block devices
*
* @args: Number of arguments to the command (argv[0] is the command itself)
* @argv: Command arguments
* @if_type: Interface type
* @cur_devnump: Current device number for this interface type
* Return: 0 if OK, CMD_RET_ERROR on error
*/
int blk_common_cmd(int argc, char *const argv[], enum if_type if_type,
int *cur_devnump);
enum blk_flag_t {
BLKF_FIXED = 1 << 0,
BLKF_REMOVABLE = 1 << 1,
BLKF_BOTH = BLKF_FIXED | BLKF_REMOVABLE,
};
/**
* blk_first_device_err() - Get the first block device
*
* The device returned is probed if necessary, and ready for use
*
* @flags: Indicates type of device to return
* @devp: Returns pointer to the first device in that uclass, or NULL if none
* Return: 0 if found, -ENODEV if not found, other -ve on error
*/
int blk_first_device_err(enum blk_flag_t flags, struct udevice **devp);
/**
* blk_next_device_err() - Get the next block device
*
* The device returned is probed if necessary, and ready for use
*
* @flags: Indicates type of device to return
* @devp: On entry, pointer to device to lookup. On exit, returns pointer
* to the next device in the uclass if no error occurred, or -ENODEV if
* there is no next device.
* Return: 0 if found, -ENODEV if not found, other -ve on error
*/
int blk_next_device_err(enum blk_flag_t flags, struct udevice **devp);
/**
* blk_find_first() - Return the first matching block device
* @flags: Indicates type of device to return
* @devp: Returns pointer to device, or NULL on error
*
* The device is not prepared for use - this is an internal function.
* The function uclass_get_device_tail() can be used to probe the device.
*
* Note that some devices are considered removable until they have been probed
*
* @return 0 if found, -ENODEV if not found
*/
int blk_find_first(enum blk_flag_t flags, struct udevice **devp);
/**
* blk_find_next() - Return the next matching block device
* @flags: Indicates type of device to return
* @devp: On entry, pointer to device to lookup. On exit, returns pointer
* to the next device in the same uclass, or NULL if none
*
* The device is not prepared for use - this is an internal function.
* The function uclass_get_device_tail() can be used to probe the device.
*
* Note that some devices are considered removable until they have been probed
*
* @return 0 if found, -ENODEV if not found
*/
int blk_find_next(enum blk_flag_t flags, struct udevice **devp);
/**
* blk_foreach() - iterate through block devices
*
* This creates a for() loop which works through the available block devices in
* order from start to end.
*
* If for some reason the uclass cannot be found, this does nothing.
*
* @_flags: Indicates type of device to return
* @_pos: struct udevice * to hold the current device. Set to NULL when there
* are no more devices.
*/
#define blk_foreach(_flags, _pos) \
for (int _ret = blk_find_first(_flags, &_pos); !_ret && _pos; \
_ret = blk_find_next(_flags, &_pos))
/**
* blk_foreach_probe() - Helper function to iteration through block devices
*
* This creates a for() loop which works through the available devices in
* a uclass in order from start to end. Devices are probed if necessary,
* and ready for use.
*
* @flags: Indicates type of device to return
* @dev: struct udevice * to hold the current device. Set to NULL when there
* are no more devices.
*/
#define blk_foreach_probe(flags, pos) \
for (int _ret = blk_first_device_err(flags, &(pos)); \
!_ret && pos; \
_ret = blk_next_device_err(flags, &(pos)))
/**
* blk_count_devices() - count the number of devices of a particular type
*
* @flags: Indicates type of device to find
* Return: number of devices matching those flags
*/
int blk_count_devices(enum blk_flag_t flag);
#endif