sfdisk: improve -N warnings

[thirdparty/util-linux.git] / libfdisk / src / context.c

#ifdef HAVE_LIBBLKID
# include <blkid.h>
#endif

#include "fdiskP.h"


/**
 * SECTION: context
 * @title: Context
 * @short_description: stores info about device, labels etc.
 *
 * The library distinguish between three types of partitioning objects.
 *
 * on-disk data
 *    - disk label specific
 *    - probed and read  by disklabel drivers when assign device to the context
 *      or when switch to another disk label type
 *    - only fdisk_write_disklabel() modify on-disk data
 *
 * in-memory data
 *    - generic data and disklabel specific data stored in struct fdisk_label
 *    - all partitioning operations are based on in-memory data only
 *
 * struct fdisk_partition
 *    - provides abstraction to present partitions to users
 *    - fdisk_partition is possible to gather to fdisk_table container
 *    - used as unified template for new partitions
 *    - the struct fdisk_partition is always completely independent object and
 *      any change to the object has no effect to in-memory (or on-disk) label data
 */

/**
 * fdisk_new_context:
 *
 * Returns: newly allocated libfdisk handler
 */
struct fdisk_context *fdisk_new_context(void)
{
	struct fdisk_context *cxt;

	cxt = calloc(1, sizeof(*cxt));
	if (!cxt)
		return NULL;

	DBG(CXT, ul_debugobj(cxt, "alloc"));
	cxt->dev_fd = -1;
	cxt->refcount = 1;

	/*
	 * Allocate label specific structs.
	 *
	 * This is necessary (for example) to store label specific
	 * context setting.
	 */
	cxt->labels[ cxt->nlabels++ ] = fdisk_new_gpt_label(cxt);
	cxt->labels[ cxt->nlabels++ ] = fdisk_new_dos_label(cxt);
	cxt->labels[ cxt->nlabels++ ] = fdisk_new_bsd_label(cxt);
	cxt->labels[ cxt->nlabels++ ] = fdisk_new_sgi_label(cxt);
	cxt->labels[ cxt->nlabels++ ] = fdisk_new_sun_label(cxt);

	return cxt;
}

static int init_nested_from_parent(struct fdisk_context *cxt, int isnew)
{
	struct fdisk_context *parent;

	assert(cxt);
	assert(cxt->parent);

	parent = cxt->parent;

	cxt->alignment_offset = parent->alignment_offset;
	cxt->ask_cb =		parent->ask_cb;
	cxt->ask_data =		parent->ask_data;
	cxt->dev_fd =		parent->dev_fd;
	cxt->first_lba =        parent->first_lba;
	cxt->firstsector_bufsz = parent->firstsector_bufsz;
	cxt->firstsector =	parent->firstsector;
	cxt->geom =		parent->geom;
	cxt->grain =            parent->grain;
	cxt->io_size =          parent->io_size;
	cxt->last_lba =		parent->last_lba;
	cxt->min_io_size =      parent->min_io_size;
	cxt->optimal_io_size =  parent->optimal_io_size;
	cxt->phy_sector_size =  parent->phy_sector_size;
	cxt->readonly =		parent->readonly;
	cxt->script =		parent->script;
	fdisk_ref_script(cxt->script);
	cxt->sector_size =      parent->sector_size;
	cxt->total_sectors =    parent->total_sectors;
	cxt->user_geom =	parent->user_geom;
	cxt->user_log_sector =	parent->user_log_sector;
	cxt->user_pyh_sector =  parent->user_pyh_sector;

	/* parent <--> nested independent setting, initialize for new nested 
	 * contexts only */
	if (isnew) {
		cxt->listonly =	parent->listonly;
		cxt->display_details =	parent->display_details;
		cxt->display_in_cyl_units = parent->display_in_cyl_units;
	}

	free(cxt->dev_path);
	cxt->dev_path = NULL;

	if (parent->dev_path) {
		cxt->dev_path =	strdup(parent->dev_path);
		if (!cxt->dev_path)
			return -ENOMEM;
	}

	return 0;
}

/**
 * fdisk_new_nested_context:
 * @parent: parental context
 * @name: optional label name (e.g. "bsd")
 *
 * Create a new nested fdisk context for nested disk labels (e.g. BSD or PMBR).
 * The function also probes for the nested label on the device if device is
 * already assigned to parent.
 *
 * The new context is initialized according to @parent and both context shares
 * some settings and file descriptor to the device. The child propagate some
 * changes (like fdisk_assign_device()) to parent, but it does not work
 * vice-versa. The behavior is undefined if you assign another device to
 * parent.
 *
 * Returns: new context for nested partition table.
 */
struct fdisk_context *fdisk_new_nested_context(struct fdisk_context *parent,
				const char *name)
{
	struct fdisk_context *cxt;
	struct fdisk_label *lb = NULL;

	assert(parent);

	cxt = calloc(1, sizeof(*cxt));
	if (!cxt)
		return NULL;

	DBG(CXT, ul_debugobj(parent, "alloc nested [%p] [name=%s]", cxt, name));
	cxt->refcount = 1;

	fdisk_ref_context(parent);
	cxt->parent = parent;

	if (init_nested_from_parent(cxt, 1) != 0) {
		cxt->parent = NULL;
		fdisk_unref_context(cxt);
		return NULL;
	}

	if (name) {
		if (strcasecmp(name, "bsd") == 0)
			lb = cxt->labels[ cxt->nlabels++ ] = fdisk_new_bsd_label(cxt);
		else if (strcasecmp(name, "dos") == 0 || strcasecmp(name, "mbr") == 0)
			lb = cxt->labels[ cxt->nlabels++ ] = fdisk_new_dos_label(cxt);
	}

	if (lb && parent->dev_fd >= 0) {
		DBG(CXT, ul_debugobj(cxt, "probing for nested %s", lb->name));

		cxt->label = lb;

		if (lb->op->probe(cxt) == 1)
			__fdisk_switch_label(cxt, lb);
		else {
			DBG(CXT, ul_debugobj(cxt, "not found %s label", lb->name));
			if (lb->op->deinit)
				lb->op->deinit(lb);
			cxt->label = NULL;
		}
	}

	return cxt;
}


/**
 * fdisk_ref_context:
 * @cxt: context pointer
 *
 * Increments reference counter.
 */
void fdisk_ref_context(struct fdisk_context *cxt)
{
	if (cxt)
		cxt->refcount++;
}

/**
 * fdisk_get_label:
 * @cxt: context instance
 * @name: label name (e.g. "gpt")
 *
 * If no @name specified then returns the current context label.
 *
 * The label is allocated and maintained within the context #cxt. There is
 * nothing like reference counting for labels, you cannot delallocate the
 * label.
 *
 * Returns: label struct or NULL in case of error.
 */
struct fdisk_label *fdisk_get_label(struct fdisk_context *cxt, const char *name)
{
	size_t i;

	assert(cxt);

	if (!name)
		return cxt->label;
	else if (strcasecmp(name, "mbr") == 0)
		name = "dos";

	for (i = 0; i < cxt->nlabels; i++)
		if (cxt->labels[i]
		    && strcasecmp(cxt->labels[i]->name, name) == 0)
			return cxt->labels[i];

	DBG(CXT, ul_debugobj(cxt, "failed to found %s label driver", name));
	return NULL;
}

/**
 * fdisk_next_label:
 * @cxt: context instance
 * @lb: returns pointer to the next label
 *
 * <informalexample>
 *   <programlisting>
 *      // print all supported labels
 *	struct fdisk_context *cxt = fdisk_new_context();
 *	struct fdisk_label *lb = NULL;
 *
 *	while (fdisk_next_label(cxt, &lb) == 0)
 *		print("label name: %s\n", fdisk_label_get_name(lb));
 *	fdisk_unref_context(cxt);
 *   </programlisting>
 * </informalexample>
 *
 * Returns: <0 in case of error, 0 on success, 1 at the end.
 */
int fdisk_next_label(struct fdisk_context *cxt, struct fdisk_label **lb)
{
	size_t i;
	struct fdisk_label *res = NULL;

	if (!lb || !cxt)
		return -EINVAL;

	if (!*lb)
		res = cxt->labels[0];
	else {
		for (i = 1; i < cxt->nlabels; i++) {
			if (*lb == cxt->labels[i - 1]) {
				res = cxt->labels[i];
				break;
			}
		}
	}

	*lb = res;
	return res ? 0 : 1;
}

/**
 * fdisk_get_nlabels:
 * @cxt: context
 *
 * Returns: number of supported label types
 */
size_t fdisk_get_nlabels(struct fdisk_context *cxt)
{
	return cxt ? cxt->nlabels : 0;
}

int __fdisk_switch_label(struct fdisk_context *cxt, struct fdisk_label *lb)
{
	if (!lb || !cxt)
		return -EINVAL;
	if (lb->disabled) {
		DBG(CXT, ul_debugobj(cxt, "*** attempt to switch to disabled label %s -- ignore!", lb->name));
		return -EINVAL;
	}
	cxt->label = lb;
	DBG(CXT, ul_debugobj(cxt, "--> switching context to %s!", lb->name));
	return 0;
}

/**
 * fdisk_has_label:
 * @cxt: fdisk context
 *
 * Returns: return 1 if there is label on the device.
 */
int fdisk_has_label(struct fdisk_context *cxt)
{
	return cxt && cxt->label;
}

/**
 * fdisk_get_npartitions:
 * @cxt: context
 *
 * The maximal number of the partitions depends on disklabel and does not
 * have to describe the real limit of PT.
 *
 * For example the limit for MBR without extend partition is 4, with extended
 * partition it's unlimited (so the function returns the current number of all
 * partitions in this case).
 *
 * And for example for GPT it depends on space allocated on disk for array of
 * entry records (usually 128).
 *
 * It's fine to use fdisk_get_npartitions() in loops, but don't forget that
 * partition may be unused (see fdisk_is_partition_used()).
 *
 * <informalexample>
 *   <programlisting>
 *	struct fdisk_partition *pa = NULL;
 *	size_t i, nmax = fdisk_get_npartitions(cxt);
 *
 *	for (i = 0; i < nmax; i++) {
 *		if (!fdisk_is_partition_used(cxt, i))
 *			continue;
 *		... do something ...
 *	}
 *   </programlisting>
 * </informalexample>
 *
 * Note that the recommended way to list partitions is to use
 * fdisk_get_partitions() and struct fdisk_table than ask disk driver for each
 * individual partitions.
 *
 * Returns: maximal number of partitions for the current label.
 */
size_t fdisk_get_npartitions(struct fdisk_context *cxt)
{
	return cxt && cxt->label ? cxt->label->nparts_max : 0;
}

/**
 * fdisk_is_labeltype:
 * @cxt: fdisk context
 * @id: FDISK_DISKLABEL_*
 *
 * See also fdisk_is_label() macro in libfdisk.h.
 *
 * Returns: return 1 if the current label is @id
 */
int fdisk_is_labeltype(struct fdisk_context *cxt, enum fdisk_labeltype id)
{
	assert(cxt);

	return cxt->label && fdisk_label_get_type(cxt->label) == id;
}

/**
 * fdisk_get_parent:
 * @cxt: nested fdisk context
 *
 * Returns: pointer to parental context, or NULL
 */
struct fdisk_context *fdisk_get_parent(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->parent;
}

static void reset_context(struct fdisk_context *cxt)
{
	size_t i;

	DBG(CXT, ul_debugobj(cxt, "*** resetting context"));

	/* reset drives' private data */
	for (i = 0; i < cxt->nlabels; i++)
		fdisk_deinit_label(cxt->labels[i]);

	if (cxt->parent) {
		/* the first sector may be independent on parent */
		if (cxt->parent->firstsector != cxt->firstsector)
			free(cxt->firstsector);
	} else {
		/* we close device only in primary context */
		if (cxt->dev_fd > -1)
			close(cxt->dev_fd);
		free(cxt->firstsector);
	}

	free(cxt->dev_path);
	cxt->dev_path = NULL;

	cxt->dev_fd = -1;
	cxt->firstsector = NULL;
	cxt->firstsector_bufsz = 0;

	fdisk_zeroize_device_properties(cxt);

	fdisk_unref_script(cxt->script);
	cxt->script = NULL;

	cxt->label = NULL;
}

/*
 * This function prints a warning if the device is not wiped (e.g. wipefs(8).
 * Please don't call this function if there is already a PT.
 *
 * Returns: 0 if nothing found, < 0 on error, 1 if found a signature
 */
static int warn_wipe(struct fdisk_context *cxt)
{
#ifdef HAVE_LIBBLKID
	blkid_probe pr;
#endif
	int rc = 0;

	assert(cxt);

	if (fdisk_has_label(cxt) || cxt->dev_fd < 0)
		return -EINVAL;
#ifdef HAVE_LIBBLKID
	DBG(CXT, ul_debugobj(cxt, "wipe check: initialize libblkid prober"));

	pr = blkid_new_probe();
	if (!pr)
		return -ENOMEM;
	rc = blkid_probe_set_device(pr, cxt->dev_fd, 0, 0);
	if (rc)
		return rc;

	blkid_probe_enable_superblocks(pr, 1);
	blkid_probe_set_superblocks_flags(pr, BLKID_SUBLKS_TYPE);
	blkid_probe_enable_partitions(pr, 1);

	/* we care about the first found FS/raid, so don't call blkid_do_probe()
	 * in loop or don't use blkid_do_fullprobe() ... */
	rc = blkid_do_probe(pr);
	if (rc == 0) {
		const char *name = NULL;

		if (blkid_probe_lookup_value(pr, "TYPE", &name, 0) == 0 ||
		    blkid_probe_lookup_value(pr, "PTTYPE", &name, 0) == 0) {
			fdisk_warnx(cxt, _(
				"%s: device contains a valid '%s' signature; it is "
				"strongly recommended to wipe the device with "
				"wipefs(8) if this is unexpected, in order to "
				"avoid possible collisions"), cxt->dev_path, name);
			rc = 1;
		}
	}

	blkid_free_probe(pr);
#endif
	return rc;
}

/**
 * fdisk_assign_device:
 * @cxt: context
 * @fname: path to the device to be handled
 * @readonly: how to open the device
 *
 * Open the device, discovery topology, geometry, detect disklabel and switch
 * the current label driver to reflect the probing result.
 *
 * Note that this function resets all generic setting in context. If the @cxt
 * is nested context then the device is assigned to the parental context and
 * necessary properties are copied to the @cxt. The change is propagated in
 * child->parent direction only. It's impossible to use a different device for
 * primary and nested contexts.
 *
 * Returns: 0 on success, < 0 on error.
 */
int fdisk_assign_device(struct fdisk_context *cxt,
			const char *fname, int readonly)
{
	int fd;

	DBG(CXT, ul_debugobj(cxt, "assigning device %s", fname));
	assert(cxt);

	/* redirect request to parent */
	if (cxt->parent) {
		int rc, org = fdisk_is_listonly(cxt->parent);

		/* assign_device() is sensitive to "listonly" mode, so let's
		 * follow the current context setting for the parent to avoid 
		 * unwanted extra warnings. */
		fdisk_enable_listonly(cxt->parent, fdisk_is_listonly(cxt));

		rc = fdisk_assign_device(cxt->parent, fname, readonly);
		fdisk_enable_listonly(cxt->parent, org);

		if (!rc)
			rc = init_nested_from_parent(cxt, 0);
		if (!rc)
			fdisk_probe_labels(cxt);
		return rc;
	}

	reset_context(cxt);

	fd = open(fname, (readonly ? O_RDONLY : O_RDWR ) | O_CLOEXEC);
	if (fd < 0)
		return -errno;

	cxt->readonly = readonly;
	cxt->dev_fd = fd;
	cxt->dev_path = strdup(fname);
	if (!cxt->dev_path)
		goto fail;

	fdisk_discover_topology(cxt);
	fdisk_discover_geometry(cxt);

	if (fdisk_read_firstsector(cxt) < 0)
		goto fail;

	/* detect labels and apply labes specific stuff (e.g geomery)
	 * to the context */
	fdisk_probe_labels(cxt);

	/* let's apply user geometry *after* label prober
	 * to make it possible to override in-label setting */
	fdisk_apply_user_device_properties(cxt);

	/* warn about obsolete stuff on the device if we aren't in
	 * list-only mode and there is not PT yet */
	if (!fdisk_is_listonly(cxt) && !fdisk_has_label(cxt))
		warn_wipe(cxt);

	DBG(CXT, ul_debugobj(cxt, "initialized for %s [%s]",
			      fname, readonly ? "READ-ONLY" : "READ-WRITE"));
	return 0;
fail:
	DBG(CXT, ul_debugobj(cxt, "failed to assign device"));
	return -errno;
}

/**
 * fdisk_deassign_device:
 * @cxt: context
 * @nosync: disable fsync()
 *
 * Close device and call fsync(). If the @cxt is nested context than the
 * request is redirected to the parent.
 *
 * Returns: 0 on success, < 0 on error.
 */
int fdisk_deassign_device(struct fdisk_context *cxt, int nosync)
{
	assert(cxt);
	assert(cxt->dev_fd >= 0);

	if (cxt->parent) {
		int rc = fdisk_deassign_device(cxt->parent, nosync);

		if (!rc)
			rc = init_nested_from_parent(cxt, 0);
		return rc;
	}

	if (cxt->readonly)
		close(cxt->dev_fd);
	else {
		if (fsync(cxt->dev_fd) || close(cxt->dev_fd)) {
			fdisk_warn(cxt, _("%s: close device failed"),
					cxt->dev_path);
			return -errno;
		}

		if (!nosync) {
			fdisk_info(cxt, _("Syncing disks."));
			sync();
		}
	}

	free(cxt->dev_path);
	cxt->dev_path = NULL;

	cxt->dev_fd = -1;

	return 0;
}

/**
 * fdisk_is_readonly:
 * @cxt: context
 *
 * Returns: 1 if device open readonly
 */
int fdisk_is_readonly(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->readonly;
}

/**
 * fdisk_unref_context:
 * @cxt: fdisk context
 *
 * Deallocates context struct.
 */
void fdisk_unref_context(struct fdisk_context *cxt)
{
	int i;

	if (!cxt)
		return;

	cxt->refcount--;
	if (cxt->refcount <= 0) {
		DBG(CXT, ul_debugobj(cxt, "freeing context %p for %s", cxt, cxt->dev_path));

		reset_context(cxt);	/* this is sensitive to parent<->child relationship! */

		/* deallocate label's private stuff */
		for (i = 0; i < cxt->nlabels; i++) {
			if (!cxt->labels[i])
				continue;
			if (cxt->labels[i]->op->free)
				cxt->labels[i]->op->free(cxt->labels[i]);
			else
				free(cxt->labels[i]);
		}

		fdisk_unref_context(cxt->parent);
		cxt->parent = NULL;

		free(cxt);
	}
}


/**
 * fdisk_enable_details:
 * @cxt: context
 * @enable: true/flase
 *
 * Enables or disables "details" display mode. This function has effect to
 * fdisk_partition_to_string() function.
 *
 * Returns: 0 on success, < 0 on error.
 */
int fdisk_enable_details(struct fdisk_context *cxt, int enable)
{
	assert(cxt);
	cxt->display_details = enable ? 1 : 0;
	return 0;
}

/**
 * fdisk_is_details:
 * @cxt: context
 *
 * Returns: 1 if details are enabled
 */
int fdisk_is_details(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->display_details == 1;
}

/**
 * fdisk_enable_listonly:
 * @cxt: context
 * @enable: true/flase
 *
 * Just list partition only, don't care about another details, mistakes, ...
 *
 * Returns: 0 on success, < 0 on error.
 */
int fdisk_enable_listonly(struct fdisk_context *cxt, int enable)
{
	assert(cxt);
	cxt->listonly = enable ? 1 : 0;
	return 0;
}

/**
 * fdisk_is_listonly:
 * @cxt: context
 *
 * Returns: 1 if list-only mode enabled
 */
int fdisk_is_listonly(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->listonly == 1;
}


/**
 * fdisk_set_unit:
 * @cxt: context
 * @str: "cylinder" or "sector".
 *
 * This is pure shit, unfortunately for example Sun addresses begin of the
 * partition by cylinders...
 *
 * Returns: 0 on succes, <0 on error.
 */
int fdisk_set_unit(struct fdisk_context *cxt, const char *str)
{
	assert(cxt);

	cxt->display_in_cyl_units = 0;

	if (!str)
		return 0;

	if (strcmp(str, "cylinder") == 0 || strcmp(str, "cylinders") == 0)
		cxt->display_in_cyl_units = 1;

	else if (strcmp(str, "sector") == 0 || strcmp(str, "sectors") == 0)
		cxt->display_in_cyl_units = 0;

	DBG(CXT, ul_debugobj(cxt, "display unit: %s", fdisk_get_unit(cxt, 0)));
	return 0;
}

/**
 * fdisk_get_unit:
 * @cxt: context
 * @n: FDISK_PLURAL or FDISK_SINGULAR
 *
 * Returns: unit name.
 */
const char *fdisk_get_unit(struct fdisk_context *cxt, int n)
{
	assert(cxt);

	if (fdisk_use_cylinders(cxt))
		return P_("cylinder", "cylinders", n);
	return P_("sector", "sectors", n);
}

/**
 * fdisk_use_cylinders:
 * @cxt: context
 *
 * Returns: 1 if user wants to display in cylinders.
 */
int fdisk_use_cylinders(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->display_in_cyl_units == 1;
}

/**
 * fdisk_get_units_per_sector:
 * @cxt: context
 *
 * This is necessary only for brain dead situations when we use "cylinders";
 *
 * Returns: number of "units" per sector, default is 1 if display unit is sector.
 */
unsigned int fdisk_get_units_per_sector(struct fdisk_context *cxt)
{
	assert(cxt);

	if (fdisk_use_cylinders(cxt)) {
		assert(cxt->geom.heads);
		return cxt->geom.heads * cxt->geom.sectors;
	}
	return 1;
}

/**
 * fdisk_get_optimal_iosize:
 * @cxt: context
 *
 * The optimal I/O is optional and does not have to be provided by device,
 * anyway libfdisk never returns zero. If the optimal I/O size is not provided
 * then libfdisk returns minimal I/O size or sector size.
 *
 * Returns: optimal I/O size in bytes.
 */
unsigned long fdisk_get_optimal_iosize(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->optimal_io_size ? cxt->optimal_io_size : cxt->io_size;
}

/**
 * fdisk_get_minimal_iosize:
 * @cxt: context
 *
 * Returns: minimal I/O size in bytes
 */
unsigned long fdisk_get_minimal_iosize(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->min_io_size;
}

/**
 * fdisk_get_physector_size:
 * @cxt: context
 *
 * Returns: physical sector size in bytes
 */
unsigned long fdisk_get_physector_size(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->phy_sector_size;
}

/**
 * fdisk_get_sector_size:
 * @cxt: context
 *
 * Returns: logical sector size in bytes
 */
unsigned long fdisk_get_sector_size(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->sector_size;
}

/**
 * fdisk_get_alignment_offset
 * @cxt: context
 *
 * The alignment offset is offset between logical and physical sectors. For
 * backward compatibility the first logical sector on 4K disks does no have to
 * start on the same place like physical sectors.
 *
 * Returns: alignment offset in bytes
 */
unsigned long fdisk_get_alignment_offset(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->alignment_offset;
}

/**
 * fdisk_get_grain_size:
 * @cxt: context
 *
 * Returns: grain in bytes used to align partitions (usually 1MiB)
 */
unsigned long fdisk_get_grain_size(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->grain;
}

/**
 * fdisk_get_first_lba:
 * @cxt: context
 *
 * Returns: first possible LBA on disk for data partitions.
 */
fdisk_sector_t fdisk_get_first_lba(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->first_lba;
}

/**
 * fdisk_set_first_lba:
 * @cxt: fdisk context
 * @lba: first possible logical sector for data
 *
 * It's strongly recommended to use the default library setting. The first LBA
 * is always reseted by fdisk_assign_device(), fdisk_override_geometry()
 * and fdisk_reset_alignment(). This is very low level function and library
 * does not check if your setting makes any sense.
 *
 * This function is necessary only when you want to work with very unusual
 * partition tables like GPT protective MBR or hybrid partition tables on
 * bootable media where the first partition may start on very crazy offsets.
 *
 * Returns: 0 on success, <0 on error.
 */
fdisk_sector_t fdisk_set_first_lba(struct fdisk_context *cxt, fdisk_sector_t lba)
{
	assert(cxt);
	DBG(CXT, ul_debugobj(cxt, "setting first LBA from %ju to %ju",
			(uintmax_t) cxt->first_lba, (uintmax_t) lba));
	cxt->first_lba = lba;
	return 0;
}

/**
 * fdisk_get_last_lba:
 * @cxt: fdisk context
 *
 * Note that the device has to be already assigned.
 *
 * Returns: last possible LBA on device
 */
fdisk_sector_t fdisk_get_last_lba(struct fdisk_context *cxt)
{
	return cxt->last_lba;
}

/**
 * fdisk_set_last_lba:
 * @cxt: fdisk context
 * @lba: last possible logical sector
 *
 * It's strongly recommended to use the default library setting. The last LBA
 * is always reseted by fdisk_assign_device(), fdisk_override_geometry() and
 * fdisk_reset_alignment().
 *
 * The default is number of sectors on the device, but maybe modified by the
 * current disklabel driver (for example GPT uses the end of disk for backup
 * header, so last_lba is smaller than total number of sectors).
 *
 * Returns: 0 on success, <0 on error.
 */
fdisk_sector_t fdisk_set_last_lba(struct fdisk_context *cxt, fdisk_sector_t lba)
{
	assert(cxt);

	if (lba > cxt->total_sectors - 1 && lba < 1)
		return -ERANGE;
	cxt->last_lba = lba;
	return 0;
}

/**
 * fdisk_set_size_unit:
 * @cxt: fdisk context
 * @unit: FDISK_SIZEUNIT_*
 *
 * Sets unit for SIZE output field (see fdisk_partition_to_string()).
 *
 * Returns: 0 on success, <0 on error.
 */
int fdisk_set_size_unit(struct fdisk_context *cxt, int unit)
{
	assert(cxt);
	cxt->sizeunit = unit;
	return 0;
}

/**
 * fdisk_get_size_unit:
 * @cxt: fdisk context
 *
 * Gets unit for SIZE output field (see fdisk_partition_to_string()).
 *
 * Returns: unit
 */
int fdisk_get_size_units(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->sizeunit;
}

/**
 * fdisk_get_nsectors:
 * @cxt: context
 *
 * Returns: size of the device in logical sectors.
 */
fdisk_sector_t fdisk_get_nsectors(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->total_sectors;
}

/**
 * fdisk_get_devname:
 * @cxt: context
 *
 * Returns: device name.
 */
const char *fdisk_get_devname(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->dev_path;
}

/**
 * fdisk_get_devfd:
 * @cxt: context
 *
 * Retruns: device file descriptor.
 */
int fdisk_get_devfd(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->dev_fd;
}

/**
 * fdisk_get_geom_heads:
 * @cxt: context
 *
 * Returns: number of geometry heads.
 */
unsigned int fdisk_get_geom_heads(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->geom.heads;
}
/**
 * fdisk_get_geom_sectors:
 * @cxt: context
 *
 * Returns: number of geometry sectors.
 */
fdisk_sector_t fdisk_get_geom_sectors(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->geom.sectors;

}

/**
 * fdisk_get_geom_cylinders:
 * @cxt: context
 *
 * Returns: number of geometry cylinders
 */
fdisk_sector_t fdisk_get_geom_cylinders(struct fdisk_context *cxt)
{
	assert(cxt);
	return cxt->geom.cylinders;
}

int fdisk_missing_geometry(struct fdisk_context *cxt)
{
	int rc;

	assert(cxt);

	if (!cxt || !cxt->label)
		return 0;

	rc = (fdisk_label_require_geometry(cxt->label) &&
		    (!cxt->geom.heads || !cxt->geom.sectors
				      || !cxt->geom.cylinders));

	if (rc && !fdisk_is_listonly(cxt))
		fdisk_warnx(cxt, _("Incomplete geometry setting."));

	return rc;
}