[PATCH v2] dma-buf: heaps: Introduce cma_heap_add() for non-default CMA heap

[Jaskaran Singh]

From: Kunihiko Hayashi <hayashi.kunihiko at socionext.com>

Currently dma-buf heaps can handle only default CMA. This exposes
__add_cma_heap(), renamed to cma_heap_add(), as a public API to
initialize CMA heaps from a pointer to a CMA region.

At first, the driver calls of_reserved_mem_device_init() to set
memory-region property associated with reserved-memory defined as CMA
to the device. And when the driver calls this cma_heap_add() with the
struct cma attached to the device, the CMA will be added to dma-buf
heaps.

For example, prepare CMA node named "linux,cma at 10000000" and
specify the node for memory-region property. After the above calls
in the driver, a device file "/dev/dma_heap/linux,cma at 10000000"
associated with the CMA become available as dma-buf heaps.

Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko at socionext.com>
[quic_jasksing at quicinc.com: Use struct cma as the function argument]
Signed-off-by: Jaskaran Singh <quic_jasksing at quicinc.com>
---
Reviving this patch as per discussions on the MediaTek Secure Heap patch
series[1]. There is now a potential client of the cma_heap_add() API.

An unaddressed problem in this patch is the proper parsing of heap
names. Naming convention for fixed address heaps in the devicetree is of
the format "[heap name]@[fixed address]", for example
"audio-heap at 88b00000". Exposing heaps this way to userspace could
prove erroneous as the usecases fulfilled by these heaps are the same
across individual SoCs. Userspace clients of these heaps might expect a
more consistent interface. Any feedback on this is appreciated.

Changes v1->v2:
- Change the function argument for dma_heap_add_cma() from struct
  device to struct cma as per the discussion on [1].
- In lieu of the above point, discard dma_heap_add_cma() and instead
  expose the existing __add_cma_heap() as cma_heap_add().
- Make minor modifications to the commit message based on the changes in
  this version. Retain most of the original commit message.

v1: https://lore.kernel.org/lkml/1594948208-4739-1-git-send-email-hayashi.kunihiko@socionext.com/

[1] https://lore.kernel.org/lkml/20230911023038.30649-1-yong.wu@mediatek.com/T/#m5184a1e13767bb656a4a3d9bf5a1fd7450e42eb7

 drivers/dma-buf/heaps/cma_heap.c | 12 ++++++++++--
 include/linux/dma-heap.h         | 10 ++++++++++
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c
index ee899f8e6721..b3bef8206e8b 100644
--- a/drivers/dma-buf/heaps/cma_heap.c
+++ b/drivers/dma-buf/heaps/cma_heap.c
@@ -367,7 +367,14 @@ static const struct dma_heap_ops cma_heap_ops = {
 	.allocate = cma_heap_allocate,
 };
 
-static int __add_cma_heap(struct cma *cma, void *data)
+/**
+ * cma_heap_add - adds a CMA heap to dmabuf heaps
+ * @cma:       pointer to the CMA pool to register the heap for
+ * @data:      unused
+ *
+ * Returns 0 on success. Else, returns errno.
+ */
+int cma_heap_add(struct cma *cma, void *data)
 {
 	struct cma_heap *cma_heap;
 	struct dma_heap_export_info exp_info;
@@ -391,6 +398,7 @@ static int __add_cma_heap(struct cma *cma, void *data)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(cma_heap_add);
 
 static int add_default_cma_heap(void)
 {
@@ -398,7 +406,7 @@ static int add_default_cma_heap(void)
 	int ret = 0;
 
 	if (default_cma)
-		ret = __add_cma_heap(default_cma, NULL);
+		ret = cma_heap_add(default_cma, NULL);
 
 	return ret;
 }
diff --git a/include/linux/dma-heap.h b/include/linux/dma-heap.h
index 0c05561cad6e..adcd462825a8 100644
--- a/include/linux/dma-heap.h
+++ b/include/linux/dma-heap.h
@@ -12,6 +12,7 @@
 #include <linux/cdev.h>
 #include <linux/types.h>
 
+struct cma;
 struct dma_heap;
 
 /**
@@ -65,4 +66,13 @@ const char *dma_heap_get_name(struct dma_heap *heap);
  */
 struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info);
 
+#ifdef CONFIG_DMABUF_HEAPS_CMA
+int cma_heap_add(struct cma *cma, void *data);
+#else
+static inline int cma_heap_add(struct cma *cma, void *data)
+{
+	return -EINVAL;
+}
+#endif /* CONFIG_DMABUF_HEAPS_CMA */
+
 #endif /* _DMA_HEAPS_H */
-- 
2.17.1