freebsd man page for g_write_data

G_DATA(9)						   BSD Kernel Developer's Manual						 G_DATA(9)

NAME
     g_read_data, g_write_data -- read/write data from/to GEOM consumer

SYNOPSIS
     #include <geom/geom.h>

     void *
     g_read_data(struct g_consumer *cp, off_t offset, off_t length, int *error);

     int
     g_write_data(struct g_consumer *cp, off_t offset, void *ptr, off_t length);

DESCRIPTION
     The g_read_data() function reads length bytes of data from the provider attached to consumer cp, starting at offset offset.  The buffer
     returned from g_read_data() is allocated with g_malloc(), so it should be freed by the caller with g_free() after use.  If the operation
     fails, an error value will be stored in the error argument if it is not NULL.

     The g_write_data() function writes length bytes of data from the buffer pointed to by ptr to the provider attached to consumer cp, starting
     at offset offset.

RESTRICTIONS
/CONDITIONS
     The length argument should be a multiple of the provider's sectorsize and less than or equal to DFLTPHYS (DFLTPHYS is defined in
     <sys/param.h>).

     The topology lock must not be held.

RETURN VALUES
     The g_read_data() function returns a pointer to a data buffer or NULL if an error occurred.  In that case an error value is stored in the
     error argument unless it is NULL.

     The g_write_data() function returns 0 if successful; otherwise an error code is returned.

ERRORS
     Possible errors:

     [EIO]		An I/O error occurred while reading from or writing to the consumer.

SEE ALSO
     geom(4), DECLARE_GEOM_CLASS(9), g_access(9), g_attach(9), g_bio(9), g_consumer(9), g_event(9), g_geom(9), g_provider(9),
     g_provider_by_name(9), g_wither_geom(9)

AUTHORS
     This manual page was written by Pawel Jakub Dawidek <pjd@FreeBSD.org>.

BSD
								 January 16, 2004							       BSD