From a0bf0e0686520865ecf8667b0ef92f604b5bdd59 Mon Sep 17 00:00:00 2001
From: Wim Taymans <wtaymans@redhat.com>
Date: Mon, 29 Nov 2021 11:07:13 +0100
Subject: [PATCH] buffers: improve fallback memory allocation

If one of the link ports is remote, enforce shared memory for the
buffer data. We must not use MemPtr because it will not be possible
to transfer this to the remote client.

If none of the sides selected any buffer type but we need shared
memory for the data, select MemFd as the fallback. This avoids using
DmaBuf, that the client did not explicitly select.
---
 src/pipewire/buffers.c   | 4 ++++
 src/pipewire/buffers.h   | 1 +
 src/pipewire/impl-link.c | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/src/pipewire/buffers.c b/src/pipewire/buffers.c
index 1ba98b183..f15f75753 100644
--- a/src/pipewire/buffers.c
+++ b/src/pipewire/buffers.c
@@ -319,6 +319,10 @@ int pw_buffers_negotiate(struct pw_context *context, uint32_t flags,
 		max_buffers = 2;
 	}
 
+	if (types == SPA_ID_INVALID &&
+	    SPA_FLAG_IS_SET(flags, PW_BUFFERS_FLAG_SHARED_MEM))
+		types = 1<<SPA_DATA_MemFd;
+
 	if (SPA_FLAG_IS_SET(flags, PW_BUFFERS_FLAG_NO_MEM))
 		minsize = 0;
 
diff --git a/src/pipewire/buffers.h b/src/pipewire/buffers.h
index d20bdbb8c..df72bf3f8 100644
--- a/src/pipewire/buffers.h
+++ b/src/pipewire/buffers.h
@@ -47,6 +47,7 @@ extern "C" {
 #define PW_BUFFERS_FLAG_NO_MEM		(1<<0)	/**< don't allocate buffer memory */
 #define PW_BUFFERS_FLAG_SHARED		(1<<1)	/**< buffers can be shared */
 #define PW_BUFFERS_FLAG_DYNAMIC		(1<<2)	/**< buffers have dynamic data */
+#define PW_BUFFERS_FLAG_SHARED_MEM	(1<<3)	/**< buffers need shared memory */
 
 struct pw_buffers {
 	struct pw_memblock *mem;	/**< allocated buffer memory */
diff --git a/src/pipewire/impl-link.c b/src/pipewire/impl-link.c
index b357d97ab..178cea079 100644
--- a/src/pipewire/impl-link.c
+++ b/src/pipewire/impl-link.c
@@ -516,6 +516,9 @@ static int do_allocation(struct pw_impl_link *this)
 		flags = 0;
 		/* always shared buffers for the link */
 		alloc_flags = PW_BUFFERS_FLAG_SHARED;
+		if (output->node->remote || input->node->remote)
+			alloc_flags |= PW_BUFFERS_FLAG_SHARED_MEM;
+
 		/* if output port can alloc buffers, alloc skeleton buffers */
 		if (SPA_FLAG_IS_SET(out_flags, SPA_PORT_FLAG_CAN_ALLOC_BUFFERS)) {
 			SPA_FLAG_SET(alloc_flags, PW_BUFFERS_FLAG_NO_MEM);