[PATCH v25 14/16] docs: describe virtio-sound capture options

[Joonho Lee]

Document request-owned capture in the ALSA configuration guide,
including MMU vmalloc page rounding, retained allocation lifetime and
the copy into the ALSA ring.

Describe the two default-off compatibility parameters in the kernel
parameter guide. Native capture pause uses STOP and START. The optional
restart path uses STOP and RELEASE at pause, then PREPARE and START on
resume.

Assisted-by: LLM
Signed-off-by: Joonho Lee <mynameisjune111@xxxxxxxxx>

---
Documentation/admin-guide/kernel-parameters.txt |   14 ++++++++++++++
 Documentation/sound/alsa-configuration.rst      |   15 +++++++++++++++
 2 files changed, 29 insertions(+)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -8344,6 +8344,20 @@
 
 			Can be used multiple times for multiple devices.
 
+	virtio_snd.capture_packed_status= [HW,ALSA]
+			Read an explicitly enabled packed status trailer after
+			the returned capture data. The fixed status scatterlist is
+			used by default.
+			Format: <bool>
+			Default: false.
+
+	virtio_snd.capture_pause_restart= [HW,ALSA]
+			Stop and release the stream when pausing capture. On
+			resume, send PREPARE and START. If disabled, pause uses
+			STOP and START while retaining the prepared stream.
+			Format: <bool>
+			Default: false.
+
 	vga=		[BOOT,X86-32] Select a particular video mode
 			See Documentation/arch/x86/boot.rst and
 			Documentation/admin-guide/svga.rst.
diff --git a/Documentation/sound/alsa-configuration.rst b/Documentation/sound/alsa-configuration.rst
--- a/Documentation/sound/alsa-configuration.rst
+++ b/Documentation/sound/alsa-configuration.rst
@@ -2537,6 +2537,21 @@
 
 This module supports multiple cards.
 
+Module virtio-snd
+-----------------
+
+Virtio-sound capture receives data into a separate request buffer for each
+PCM period. The driver validates the responses and appends frame-aligned audio
+to the ALSA ring in request order. Valid short responses are retained. Empty
+responses are accepted only during bounded startup or for requests already in
+flight at STOP or PAUSE.
+
+On MMU systems, the request buffers are vmalloc-backed and page-rounded
+individually. Allocator rounding can make total additional memory exceed the
+ALSA ring size, especially with small periods. The request buffers remain
+allocated from hw_params until hw_free.
+Captured audio is copied from each request buffer into the ALSA ring.
+
 Module snd-virtuoso
 -------------------