[PATCH] virtio-blk: clarify descriptor-segment relation

[Laura Loghin <lauralg@amazon.com>]

Regarding the relation between data descriptors and segments, the
commit that added discard and write zeroes to the spec, stated that
the idea is "using 16 Bytes payload to support 1 descriptor" (not, for
example, 32 bytes). There wasn't any mention in the spec about one data
descriptor corresponding to exactly one segment. Added this constraint
to block documentation.

Signed-off-by: Laura Loghin <lauralg@amazon.com>
---
 content.tex | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/content.tex b/content.tex
index 620c0e2..6393b68 100644
--- a/content.tex
+++ b/content.tex
@@ -4599,8 +4599,9 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope
 of 512 bytes).
 
 The \field{data} used for discard or write zeroes commands consists of one or
-more segments.  The maximum number of segments is \field{max_discard_seg} for
-discard commands and \field{max_write_zeroes_seg} for write zeroes commands.
+more segments, and one data descriptor corresponds to exactly one such segment.
+The maximum number of segments is \field{max_discard_seg} for discard commands
+and \field{max_write_zeroes_seg} for write zeroes commands.
 Each segment is of form:
 
 \begin{lstlisting}
-- 
2.17.1




Amazon Development Center (Romania) S.R.L. registered office: 27A Sf. Lazar Street, UBC5, floor 2, Iasi, Iasi County, 700045, Romania. Registered in Romania. Registration number J22/2621/2005.