On Tue, 5 May 2026 16:05:08 +0200 Ketil Johnsen <[email protected]> wrote:
> From: John Stultz <[email protected]> > > 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 <[email protected]> > Signed-off-by: T.J. Mercier <[email protected]> > Signed-off-by: Yong Wu <[email protected]> > [Yong: Fix the checkpatch alignment warning] > Signed-off-by: Yunfei Dong <[email protected]> > Signed-off-by: Florent Tomasin <[email protected]> > [Florent: Rebase] > Signed-off-by: Ketil Johnsen <[email protected]> > [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); > 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) 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 */
