From mboxrd@z Thu Jan  1 00:00:00 1970
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Subject: Re: [PATCH 1 of 2] blkfront: sector size > 512
Date: Fri, 22 May 2009 15:31:28 +0100
Message-ID: <4A16B740.90809@eu.citrix.com>
References: <C63AA5FE.6E47%keir.fraser@eu.citrix.com>
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To: Keir Fraser <Keir.Fraser@eu.citrix.com>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>, xen-devel <xen-devel@lists.xensource.com>
List-Id: xen-devel@lists.xenproject.org

Keir Fraser wrote:

> 
> Yeah, I'd take a patch to add a nice clear comment about this to blkif.h.
> ;-)
> 



Is this comment clear enough?

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

---


diff -r 61404d971c92 xen/include/public/io/blkif.h
--- a/xen/include/public/io/blkif.h	Thu May 21 04:31:47 2009 +0100
+++ b/xen/include/public/io/blkif.h	Fri May 22 15:29:19 2009 +0100
@@ -84,6 +84,13 @@
  */
 #define BLKIF_MAX_SEGMENTS_PER_REQUEST 11
 
+/* 
+ * first_sect and last_sect in blkif_request_segment, as well as
+ * sector_number in blkif_request are all expressed in 512 bytes units,
+ * however they must be properly aligned to the real sector size of
+ * the physical disk (as reported in the "sector-size" node in backend
+ * xenbus info).
+ */
 struct blkif_request_segment {
     grant_ref_t gref;        /* reference to I/O buffer frame        */
     /* @first_sect: first sector in frame to transfer (inclusive).   */