From: Maxime Ripard <mripard@kernel.org>
Date: Mon, 13 Oct 2025 08:35:17 +0000 (+0200)
Subject: dma-buf: heaps: cma: Register list of CMA regions at boot
X-Git-Tag: v6.19-rc1~157^2~23^2~23
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8b5690d5c942a80535f095c8965028262d4ab0f7;p=thirdparty%2Fkernel%2Flinux.git

dma-buf: heaps: cma: Register list of CMA regions at boot

In order to create a CMA heap instance for each CMA region found in the
system, we need to register each of these instances.

While it would appear trivial, the CMA regions are created super early
in the kernel boot process, before most of the subsystems are
initialized. Thus, we can't just create an exported function to create a
heap from the CMA region being initialized.

What we can do however is create a two-step process, where we collect
all the CMA regions into an array early on, and then when we initialize
the heaps we iterate over that array and create the heaps from the CMA
regions we collected.

Reviewed-by: T.J. Mercier <tjmercier@google.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Link: https://lore.kernel.org/r/20251013-dma-buf-ecc-heap-v8-2-04ce150ea3d9@kernel.org
---

diff --git a/MAINTAINERS b/MAINTAINERS
index f9f985c7d7479..cbfbdf722dc8f 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -7308,6 +7308,7 @@ F:	Documentation/userspace-api/dma-buf-alloc-exchange.rst
 F:	drivers/dma-buf/
 F:	include/linux/*fence.h
 F:	include/linux/dma-buf.h
+F:	include/linux/dma-buf/
 F:	include/linux/dma-resv.h
 K:	\bdma_(?:buf|fence|resv)\b
 
diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
index 0df0071119754..2a901af635ed7 100644
--- a/drivers/dma-buf/heaps/cma_heap.c
+++ b/drivers/dma-buf/heaps/cma_heap.c
@@ -14,6 +14,7 @@
 
 #include <linux/cma.h>
 #include <linux/dma-buf.h>
+#include <linux/dma-buf/heaps/cma.h>
 #include <linux/dma-heap.h>
 #include <linux/dma-map-ops.h>
 #include <linux/err.h>
@@ -27,6 +28,19 @@
 
 #define DEFAULT_CMA_NAME "default_cma_region"
 
+static struct cma *dma_areas[MAX_CMA_AREAS] __initdata;
+static unsigned int dma_areas_num __initdata;
+
+int __init dma_heap_cma_register_heap(struct cma *cma)
+{
+	if (dma_areas_num >= ARRAY_SIZE(dma_areas))
+		return -EINVAL;
+
+	dma_areas[dma_areas_num++] = cma;
+
+	return 0;
+}
+
 struct cma_heap {
 	struct dma_heap *heap;
 	struct cma *cma;
diff --git a/include/linux/dma-buf/heaps/cma.h b/include/linux/dma-buf/heaps/cma.h
new file mode 100644
index 0000000000000..e751479e21e70
--- /dev/null
+++ b/include/linux/dma-buf/heaps/cma.h
@@ -0,0 +1,16 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef DMA_BUF_HEAP_CMA_H_
+#define DMA_BUF_HEAP_CMA_H_
+
+struct cma;
+
+#ifdef CONFIG_DMABUF_HEAPS_CMA
+int dma_heap_cma_register_heap(struct cma *cma);
+#else
+static inline int dma_heap_cma_register_heap(struct cma *cma)
+{
+	return 0;
+}
+#endif // CONFIG_DMABUF_HEAPS_CMA
+
+#endif // DMA_BUF_HEAP_CMA_H_