Re: [PATCH v3 1/6] dma-buf: dma-heap: Keep track of the heap device struct

[Andrew Davis]

On 3/6/26 4:36 AM, Albert Esteve wrote:

From: John Stultz <john.stu...@linaro.org>

Keep track of the heap device struct.

This will be useful for special DMA allocations
and actions.

Signed-off-by: John Stultz <john.stu...@linaro.org>
Reviewed-by: Maxime Ripard <mrip...@kernel.org>
Signed-off-by: Albert Esteve <aest...@redhat.com>
---
  drivers/dma-buf/dma-heap.c | 34 ++++++++++++++++++++++++++--------
  include/linux/dma-heap.h   |  2 ++
  2 files changed, 28 insertions(+), 8 deletions(-)

diff --git a/drivers/dma-buf/dma-heap.c b/drivers/dma-buf/dma-heap.c
index ac5f8685a6494..1124d63eb1398 100644
--- a/drivers/dma-buf/dma-heap.c
+++ b/drivers/dma-buf/dma-heap.c
@@ -31,6 +31,7 @@
   * @heap_devt:                heap device node
   * @list:             list head connecting to list of heaps
   * @heap_cdev:                heap char device
+ * @heap_dev:          heap device
   *
   * Represents a heap of memory from which buffers can be made.
   */
@@ -41,6 +42,7 @@ struct dma_heap {
        dev_t heap_devt;
        struct list_head list;
        struct cdev heap_cdev;
+       struct device *heap_dev;
  };

static LIST_HEAD(heap_list);

@@ -223,6 +225,19 @@ const char *dma_heap_get_name(struct dma_heap *heap)
  }
  EXPORT_SYMBOL_NS_GPL(dma_heap_get_name, "DMA_BUF_HEAP");

+/**

+ * dma_heap_get_dev() - get device struct for the heap
+ * @heap: DMA-Heap to retrieve device struct from
+ *
+ * Returns:
+ * The device struct for the heap.
+ */
+struct device *dma_heap_get_dev(struct dma_heap *heap)
+{
+       return heap->heap_dev;
+}
+EXPORT_SYMBOL_NS_GPL(dma_heap_get_dev, "DMA_BUF_HEAP");
+
  /**
   * dma_heap_add - adds a heap to dmabuf heaps
   * @exp_info: information needed to register this heap
@@ -230,7 +245,6 @@ EXPORT_SYMBOL_NS_GPL(dma_heap_get_name, "DMA_BUF_HEAP");
  struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)
  {
        struct dma_heap *heap, *h, *err_ret;
-       struct device *dev_ret;
        unsigned int minor;
        int ret;

@@ -272,14 +286,14 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)

                goto err1;
        }

- dev_ret = device_create(dma_heap_class,

-                               NULL,
-                               heap->heap_devt,
-                               NULL,
-                               heap->name);
-       if (IS_ERR(dev_ret)) {
+       heap->heap_dev = device_create(dma_heap_class,
+                                      NULL,
+                                      heap->heap_devt,
+                                      NULL,
+                                      heap->name);
+       if (IS_ERR(heap->heap_dev)) {
                pr_err("dma_heap: Unable to create device\n");
-               err_ret = ERR_CAST(dev_ret);
+               err_ret = ERR_CAST(heap->heap_dev);
                goto err2;
        }

@@ -295,6 +309,10 @@ struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info)

                }
        }

+ /* Make sure it doesn't disappear on us */

+       heap->heap_dev = get_device(heap->heap_dev);
+
+

Is this actually something that matters or could happen? Seems you
just remove it in the next patch anyway.

Andrew

        /* Add heap to the list */
        list_add(&heap->list, &heap_list);
        mutex_unlock(&heap_list_lock);
diff --git a/include/linux/dma-heap.h b/include/linux/dma-heap.h
index 648328a64b27e..493085e69b70e 100644
--- a/include/linux/dma-heap.h
+++ b/include/linux/dma-heap.h
@@ -12,6 +12,7 @@
  #include <linux/types.h>

struct dma_heap;

+struct device;

/**

   * struct dma_heap_ops - ops to operate on a given heap
@@ -43,6 +44,7 @@ struct dma_heap_export_info {
  void *dma_heap_get_drvdata(struct dma_heap *heap);

const char *dma_heap_get_name(struct dma_heap *heap);

+struct device *dma_heap_get_dev(struct dma_heap *heap);

struct dma_heap *dma_heap_add(const struct dma_heap_export_info *exp_info);