[PATCH v2 1/1] Documentation: hyperv: Update documentation for sending VMBus packets

[Michael Kelley <mhkelley58@gmail.com>]

The functions for sending VMBus packets have changed.
vmbus_sendpacket_mpb_desc() can target multiple ranges, and
vmbus_sendpacket_pagebuffer() has been removed. vmbus_sendpacket_getid()
has been added. Update the documentation accordingly.

Fixes: 45a442fe369e ("Drivers: hv: vmbus: Remove vmbus_sendpacket_pagebuffer()")
Cc: stable@vger.kernel.org
Signed-off-by: Michael Kelley <mhklinux@outlook.com>
---
Changes in v2:
* Add vmbus_sendpacket_getid() to the documentation. [Naman Jain]

 Documentation/virt/hyperv/vmbus.rst | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/Documentation/virt/hyperv/vmbus.rst b/Documentation/virt/hyperv/vmbus.rst
index 654bb4849972..9c5b712c6e39 100644
--- a/Documentation/virt/hyperv/vmbus.rst
+++ b/Documentation/virt/hyperv/vmbus.rst
@@ -141,14 +141,15 @@ Three functions exist to send VMBus channel messages:
 
 1. vmbus_sendpacket():  Control-only messages and messages with
    embedded data -- no GPAs
-2. vmbus_sendpacket_pagebuffer(): Message with list of GPAs
-   identifying data to transfer.  An offset and length is
-   associated with each GPA so that multiple discontinuous areas
-   of guest memory can be targeted.
-3. vmbus_sendpacket_mpb_desc(): Message with list of GPAs
-   identifying data to transfer.  A single offset and length is
-   associated with a list of GPAs.  The GPAs must describe a
-   single logical area of guest memory to be targeted.
+2. vmbus_sendpacket_getid(): Similar to vmbus_sendpacket() but returns
+   a transaction ID that is matched against a reply from the Hyper-V
+   host. Useful when the struct completion (or other rendezvous data)
+   must reside on the caller's stack. By invalidating the transaction
+   ID before exiting the function due to a timeout or other error, a
+   late arrving interrupt is assured to not trash the stack.
+3. vmbus_sendpacket_mpb_desc(): Message with one or more data ranges
+   to target. Each range consists of a single offset and length plus
+   a list of GPAs that describe a logical area of guest memory.
 
 Historically, Linux guests have trusted Hyper-V to send well-formed
 and valid messages, and Linux drivers for synthetic devices did not
-- 
2.25.1