[PATCH] virtio-blk: document that the capacity field can change

[Stefan Hajnoczi <stefanha@redhat.com>]

Block devices can change size during operation. A configuration change
notification is sent by the device and the driver detects that the field
has changed. Document this behavior that has already been implemented in
Linux and QEMU since 2011.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
---
 content.tex | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/content.tex b/content.tex
index c6f116c..96d2aa9 100644
--- a/content.tex
+++ b/content.tex
@@ -4863,6 +4863,9 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope
 
 \drivernormative{\subsubsection}{Device Operation}{Device Types / Block Device / Device Operation}
 
+The driver SHOULD check if the content of the \field{capacity} field has
+changed upon receiving a configuration change notification.
+
 A driver MUST NOT submit a request which would cause a read or write
 beyond \field{capacity}.
 
@@ -4909,6 +4912,10 @@ \subsection{Device Operation}\label{sec:Device Types / Block Device / Device Ope
 
 \devicenormative{\subsubsection}{Device Operation}{Device Types / Block Device / Device Operation}
 
+The device MAY change the content of the \field{capacity} field during
+operation of the device. When this happens, the device SHOULD trigger a
+configuration change notification.
+
 A device MUST set the \field{status} byte to VIRTIO_BLK_S_IOERR
 for a write request if the VIRTIO_BLK_F_RO feature if offered, and MUST NOT
 write any data.
-- 
2.35.1