[Xen-devel] In blkif.h, sector unit is not clear

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

I'm trying to understand the different device properties exposed on
xenstore for a block device. And there is one property that is
contradictory within blkif.h, "sectors". There are two possible units for
it, either "sector-size" or 512-byte. Which one it is?

My guess is that it does not matter too much since "sector-size" is
probably always reported as 512.

Here is the interesting part of xen/include/public/io/blkif.h:

@@ -198,1 +198,1 @@
  *------------------------- Backend Device Properties -------------------------
@@ -241,18 +241,18 @@
  * sector-size
  *      Values:         <uint32_t>
  *
  *      The logical sector size, in bytes, of the backend device.
  *
  * physical-sector-size
  *      Values:         <uint32_t>
  *
  *      The physical sector size, in bytes, of the backend device.
  *
  * sectors
  *      Values:         <uint64_t>
  *
  *      The size of the backend device, expressed in units of its logical
  *      sector size ("sector-size").

HERE: unit for "sectors" is "sector-size"

@@ -547,10 +547,10 @@
 /*
  * NB. first_sect and last_sect in blkif_request_segment, as well as
  * sector_number in blkif_request, are always expressed in 512-byte units.
  * However they must be properly aligned to the real sector size of the
  * physical disk, which is reported in the "physical-sector-size" node in
  * the backend xenbus info. Also the xenbus "sectors" node is expressed in
  * 512-byte units.
  */
 struct blkif_request_segment {
     grant_ref_t gref;        /* reference to I/O buffer frame        */

HERE: unit for "sectors" is 512-byte


Regards,

-- 
Anthony PERARD

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel