Hi,

On Thu, May 22, 2025 at 12:14:18PM -0700, Jared Kangas wrote:

The CMA heap's name in devtmpfs can vary depending on how the heap is defined. Its name defaults to "reserved", but if a CMA area is defined in the devicetree, the heap takes on the devicetree node's name, such as "default-pool" or "linux,cma". To simplify naming, unconditionally name it "default_cma_region", but keep a legacy node in place backed by the same underlying allocator for backwards compatibility.

Signed-off-by: Jared Kangas jkangas@redhat.com

Documentation/userspace-api/dma-buf-heaps.rst | 7 +++++-- drivers/dma-buf/heaps/Kconfig | 10 ++++++++++ drivers/dma-buf/heaps/cma_heap.c | 20 ++++++++++++++++++- 3 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/Documentation/userspace-api/dma-buf-heaps.rst b/Documentation/userspace-api/dma-buf-heaps.rst index 23bd0bd7b0654..1dfe5e7acd5a3 100644 --- a/Documentation/userspace-api/dma-buf-heaps.rst +++ b/Documentation/userspace-api/dma-buf-heaps.rst @@ -21,5 +21,8 @@ following heaps: usually created either through the kernel commandline through the ``cma`` parameter, a memory region Device-Tree node with the ``linux,cma-default`` property set, or through the ``CMA_SIZE_MBYTES`` or

• ``CMA_SIZE_PERCENTAGE`` Kconfig options. Depending on the platform, it
• might be called ``reserved``, ``linux,cma``, or ``default-pool``.

• ``CMA_SIZE_PERCENTAGE`` Kconfig options. The heap's name in devtmpfs is
• ``default_cma_region``. For backwards compatibility, when the
• ``DMABUF_HEAPS_CMA_LEGACY`` Kconfig option is set, a duplicate node is
• created following legacy naming conventions; the legacy name might be
• ``reserved``, ``linux,cma``, or ``default-pool``.

diff --git a/drivers/dma-buf/heaps/Kconfig b/drivers/dma-buf/heaps/Kconfig index a5eef06c42264..bb369b38b001a 100644 --- a/drivers/dma-buf/heaps/Kconfig +++ b/drivers/dma-buf/heaps/Kconfig @@ -12,3 +12,13 @@ config DMABUF_HEAPS_CMA Choose this option to enable dma-buf CMA heap. This heap is backed by the Contiguous Memory Allocator (CMA). If your system has these regions, you should say Y here.

+config DMABUF_HEAPS_CMA_LEGACY

• bool "Legacy DMA-BUF CMA Heap"
• default y
• depends on DMABUF_HEAPS_CMA
• help

•  Add a duplicate CMA-backed dma-buf heap with legacy naming derived
  

•  from the CMA area's devicetree node, or "reserved" if the area is not
  

•  defined in the devicetree. This uses the same underlying allocator as
  

•  CONFIG_DMABUF_HEAPS_CMA.
  

diff --git a/drivers/dma-buf/heaps/cma_heap.c b/drivers/dma-buf/heaps/cma_heap.c index e998d8ccd1dc6..dfeccafc6ae3c 100644 --- a/drivers/dma-buf/heaps/cma_heap.c +++ b/drivers/dma-buf/heaps/cma_heap.c @@ -9,6 +9,9 @@

• Copyright (C) 2019 Texas Instruments Incorporated - http://www.ti.com/
• Andrew F. Davis afd@ti.com

*/

+#define pr_fmt(fmt) "cma_heap: " fmt

#include <linux/cma.h> #include <linux/dma-buf.h> #include <linux/dma-heap.h> @@ -22,6 +25,7 @@ #include <linux/slab.h> #include <linux/vmalloc.h> +#define DEFAULT_CMA_NAME "default_cma_region" struct cma_heap { struct dma_heap *heap; @@ -394,15 +398,29 @@ static int __init __add_cma_heap(struct cma *cma, const char *name) static int __init add_default_cma_heap(void) { struct cma *default_cma = dev_get_cma_area(NULL);

• const char *legacy_cma_name; int ret;

if (!default_cma) return 0;

• ret = __add_cma_heap(default_cma, cma_get_name(default_cma));

• ret = __add_cma_heap(default_cma, DEFAULT_CMA_NAME); if (ret) return ret;

• if (IS_ENABLED(CONFIG_DMABUF_HEAPS_CMA_LEGACY)) {

• legacy_cma_name = cma_get_name(default_cma);
  

• if (!strcmp(legacy_cma_name, DEFAULT_CMA_NAME)) {
  

• 	pr_warn("legacy name and default name are the same, skipping legacy heap\n");
  

• 	return 0;
  

• }
  

• ret = __add_cma_heap(default_cma, legacy_cma_name);
  

• if (ret)
  

• 	pr_warn("failed to add legacy heap: %pe\n",
  

• 		ERR_PTR(-ret));
  

Are you sure about the -ret? ret should already be a negative number if it failed?

With that fixed,

Reviewed-by: Maxime Ripard mripard@kernel.org

Maxime