On Tue, 5 May 2026 16:05:08 +0200 Ketil Johnsen ketil.johnsen@arm.com wrote:
From: John Stultz jstultz@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.
I think this commit message needs to be updated with more details around what it's actually needed for here (driver needing protected buffer to boot FW and expose a char device, and no clean way to pass dmabufs around before this cdev is exposed).
Signed-off-by: John Stultz jstultz@google.com Signed-off-by: T.J. Mercier tjmercier@google.com Signed-off-by: Yong Wu yong.wu@mediatek.com [Yong: Fix the checkpatch alignment warning] Signed-off-by: Yunfei Dong yunfei.dong@mediatek.com Signed-off-by: Florent Tomasin florent.tomasin@arm.com [Florent: Rebase] Signed-off-by: Ketil Johnsen ketil.johnsen@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);
I'd probably move the flags checks to dma_heap_buffer_alloc() in a separate patch, to keep the diff easier to read. Same for the dma_heap_buffer_alloc()/dma_heap_bufferfd_alloc() split, though I'm not too sure we need dma_heap_bufferfd_alloc(), we could just move the FD allocation directly in dma_heap_ioctl_allocate().
/* * 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);@@ -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)
s/dma_heap_find/dma_heap_find_by_name/gc
+{
- 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)) {
I think we should go sysfs_streq(), to make sure we don't return a heap whose name only starts with the searched name.
mutex_unlock(&heap_list_lock);return h;}dma_heap_put(h);- }
- mutex_unlock(&heap_list_lock);
- return NULL;
This could be simplified with something like:
struct dma_heap *h, *ret = NULL;
guard(mutex)(&heap_list_lock); list_for_each_entry(h, &heap_list, list) { if (!sysfs_streq(h->name, name)) continue;
if (kref_get_unless_zero(&h->refcount)) ret = h;
break; }
return ret;
+}
+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 */