ia64/xen-unstable

changeset 19640:cc682927d123

blkif: Clarify units for 'sector'-sized blkif request params.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
author Keir Fraser <keir.fraser@citrix.com>
date Tue May 26 10:01:54 2009 +0100 (2009-05-26)
parents 205b1badbcfd
children caa8c0e2d6f6
files xen/include/public/io/blkif.h
line diff
     1.1 --- a/xen/include/public/io/blkif.h	Tue May 26 09:58:38 2009 +0100
     1.2 +++ b/xen/include/public/io/blkif.h	Tue May 26 10:01:54 2009 +0100
     1.3 @@ -84,6 +84,13 @@
     1.4   */
     1.5  #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
     1.6  
     1.7 +/* 
     1.8 + * NB. first_sect and last_sect in blkif_request_segment, as well as
     1.9 + * sector_number in blkif_request, are always expressed in 512-byte units.
    1.10 + * However they must be properly aligned to the real sector size of the
    1.11 + * physical disk, which is reported in the "sector-size" node in the backend
    1.12 + * xenbus info. Also the xenbus "sectors" node is expressed in 512-byte units.
    1.13 + */
    1.14  struct blkif_request_segment {
    1.15      grant_ref_t gref;        /* reference to I/O buffer frame        */
    1.16      /* @first_sect: first sector in frame to transfer (inclusive).   */