[PATCH 2/8] dma-heap: Provide accessors so that in-kernel drivers can allocate dmabufs from specific heaps

[Ketil Johnsen]

From: John Stultz <jstultz at google.com>

This allows drivers who don't want to create their own
DMA-BUF exporter to be able to allocate DMA-BUFs directly
from existing DMA-BUF Heaps.

There is some concern that the premise of DMA-BUF heaps is
that userland knows better about what type of heap memory
is needed for a pipeline, so it would likely be best for
drivers to import and fill DMA-BUFs allocated by userland
instead of allocating one themselves, but this is still
up for debate.

Signed-off-by: John Stultz <jstultz at google.com>
Signed-off-by: T.J. Mercier <tjmercier at google.com>
Signed-off-by: Yong Wu <yong.wu at mediatek.com>
[Yong: Fix the checkpatch alignment warning]
Signed-off-by: Yunfei Dong <yunfei.dong at mediatek.com>
Signed-off-by: Florent Tomasin <florent.tomasin at arm.com>
[Florent: Rebase]
Signed-off-by: Ketil Johnsen <ketil.johnsen at arm.com>
[Ketil: Rebase]
---
 drivers/dma-buf/dma-heap.c | 80 ++++++++++++++++++++++++++++++--------
 include/linux/dma-heap.h   |  6 +++
 2 files changed, 70 insertions(+), 16 deletions(-)

diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
index 9fd365ddbd517..854d40d789ff2 100644
--- a/drivers/dma-buf/dma-heap.c
+++ b/drivers/dma-buf/dma-heap.c
@@ -57,12 +57,24 @@ module_param(mem_accounting, bool, 0444);
 MODULE_PARM_DESC(mem_accounting,
 		 "Enable cgroup-based memory accounting for dma-buf heap allocations (default=false).");
 
-static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
-				 u32 fd_flags,
-				 u64 heap_flags)
+/**
+ * dma_heap_buffer_alloc - Allocate dma-buf from a dma_heap
+ * @heap:	DMA-Heap to allocate from
+ * @len:	size to allocate in bytes
+ * @fd_flags:	flags to set on returned dma-buf fd
+ * @heap_flags: flags to pass to the dma heap
+ *
+ * This is for internal dma-buf allocations only. Free returned buffers with dma_buf_put().
+ */
+struct dma_buf *dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
+				      u32 fd_flags,
+				      u64 heap_flags)
 {
-	struct dma_buf *dmabuf;
-	int fd;
+	if (fd_flags & ~DMA_HEAP_VALID_FD_FLAGS)
+		return ERR_PTR(-EINVAL);
+
+	if (heap_flags & ~DMA_HEAP_VALID_HEAP_FLAGS)
+		return ERR_PTR(-EINVAL);
 
 	/*
 	 * Allocations from all heaps have to begin
@@ -70,9 +82,20 @@ static int dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
 	 */
 	len = PAGE_ALIGN(len);
 	if (!len)
-		return -EINVAL;
+		return ERR_PTR(-EINVAL);
+
+	return heap->ops->allocate(heap, len, fd_flags, heap_flags);
+}
+EXPORT_SYMBOL_NS_GPL(dma_heap_buffer_alloc, "DMA_BUF_HEAP");
 
-	dmabuf = heap->ops->allocate(heap, len, fd_flags, heap_flags);
+static int dma_heap_bufferfd_alloc(struct dma_heap *heap, size_t len,
+				   u32 fd_flags,
+				   u64 heap_flags)
+{
+	struct dma_buf *dmabuf;
+	int fd;
+
+	dmabuf = dma_heap_buffer_alloc(heap, len, fd_flags, heap_flags);
 	if (IS_ERR(dmabuf))
 		return PTR_ERR(dmabuf);
 
@@ -110,15 +133,9 @@ static long dma_heap_ioctl_allocate(struct file *file, void *data)
 	if (heap_allocation->fd)
 		return -EINVAL;
 
-	if (heap_allocation->fd_flags & ~DMA_HEAP_VALID_FD_FLAGS)
-		return -EINVAL;
-
-	if (heap_allocation->heap_flags & ~DMA_HEAP_VALID_HEAP_FLAGS)
-		return -EINVAL;
-
-	fd = dma_heap_buffer_alloc(heap, heap_allocation->len,
-				   heap_allocation->fd_flags,
-				   heap_allocation->heap_flags);
+	fd = dma_heap_bufferfd_alloc(heap, heap_allocation->len,
+				     heap_allocation->fd_flags,
+				     heap_allocation->heap_flags);
 	if (fd < 0)
 		return fd;
 
@@ -317,6 +334,36 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
 }
 EXPORT_SYMBOL_NS_GPL(dma_heap_add, "DMA_BUF_HEAP");
 
+/**
+ * dma_heap_find - get the heap registered with the specified name
+ * @name: Name of the DMA-Heap to find
+ *
+ * Returns:
+ * The DMA-Heap with the provided name.
+ *
+ * NOTE: DMA-Heaps returned from this function MUST be released using
+ * dma_heap_put() when the user is done to enable the heap to be unloaded.
+ */
+struct dma_heap *dma_heap_find(const char *name)
+{
+	struct dma_heap *h;
+
+	mutex_lock(&heap_list_lock);
+	list_for_each_entry(h, &heap_list, list) {
+		if (!kref_get_unless_zero(&h->refcount))
+			continue;
+
+		if (!strcmp(h->name, name)) {
+			mutex_unlock(&heap_list_lock);
+			return h;
+		}
+		dma_heap_put(h);
+	}
+	mutex_unlock(&heap_list_lock);
+	return NULL;
+}
+EXPORT_SYMBOL_NS_GPL(dma_heap_find, "DMA_BUF_HEAP");
+
 static void dma_heap_release(struct kref *ref)
 {
 	struct dma_heap *heap = container_of(ref, struct dma_heap, refcount);
@@ -341,6 +388,7 @@ void dma_heap_put(struct dma_heap *heap)
 {
 	kref_put(&heap->refcount, dma_heap_release);
 }
+EXPORT_SYMBOL_NS_GPL(dma_heap_put, "DMA_BUF_HEAP");
 
 static char *dma_heap_devnode(const struct device *dev, umode_t *mode)
 {
diff --git a/include/linux/dma-heap.h b/include/linux/dma-heap.h
index ff57741700f5f..c3351f8a1f8cf 100644
--- a/include/linux/dma-heap.h
+++ b/include/linux/dma-heap.h
@@ -46,8 +46,14 @@ const char *dma_heap_get_name(struct dma_heap *heap);
 
 struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info);
 
+struct dma_heap *dma_heap_find(const char *name);
+
 void dma_heap_put(struct dma_heap *heap);
 
+struct dma_buf *dma_heap_buffer_alloc(struct dma_heap *heap, size_t len,
+				      u32 fd_flags,
+				      u64 heap_flags);
+
 extern bool mem_accounting;
 
 #endif /* _DMA_HEAPS_H */
-- 
2.43.0