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>.