#include <linux/list.h>
#include <linux/dma-mapping.h>
#include <linux/fs.h>
-#include <linux/fence.h>
+#include <linux/dma-fence.h>
#include <linux/wait.h>
struct device;
/**
* struct dma_buf_ops - operations possible on struct dma_buf
- * @attach: [optional] allows different devices to 'attach' themselves to the
- * given buffer. It might return -EBUSY to signal that backing storage
- * is already allocated and incompatible with the requirements
- * of requesting device.
- * @detach: [optional] detach a given device from this buffer.
- * @map_dma_buf: returns list of scatter pages allocated, increases usecount
- * of the buffer. Requires atleast one attach to be called
- * before. Returned sg list should already be mapped into
- * _device_ address space. This call may sleep. May also return
- * -EINTR. Should return -EINVAL if attach hasn't been called yet.
- * @unmap_dma_buf: decreases usecount of buffer, might deallocate scatter
- * pages.
- * @release: release this buffer; to be called after the last dma_buf_put.
* @begin_cpu_access: [optional] called before cpu access to invalidate cpu
* caches and allocate backing storage (if not yet done)
* respectively pin the object into memory.
* @vunmap: [optional] unmaps a vmap from the buffer
*/
struct dma_buf_ops {
+ /**
+ * @attach:
+ *
+ * This is called from dma_buf_attach() to make sure that a given
+ * &device can access the provided &dma_buf. Exporters which support
+ * buffer objects in special locations like VRAM or device-specific
+ * carveout areas should check whether the buffer could be move to
+ * system memory (or directly accessed by the provided device), and
+ * otherwise need to fail the attach operation.
+ *
+ * The exporter should also in general check whether the current
+ * allocation fullfills the DMA constraints of the new device. If this
+ * is not the case, and the allocation cannot be moved, it should also
+ * fail the attach operation.
+ *
+ * Any exporter-private housekeeping data can be stored in the priv
+ * pointer of &dma_buf_attachment structure.
+ *
+ * This callback is optional.
+ *
+ * Returns:
+ *
+ * 0 on success, negative error code on failure. It might return -EBUSY
+ * to signal that backing storage is already allocated and incompatible
+ * with the requirements of requesting device.
+ */
int (*attach)(struct dma_buf *, struct device *,
- struct dma_buf_attachment *);
+ struct dma_buf_attachment *);
+ /**
+ * @detach:
+ *
+ * This is called by dma_buf_detach() to release a &dma_buf_attachment.
+ * Provided so that exporters can clean up any housekeeping for an
+ * &dma_buf_attachment.
+ *
+ * This callback is optional.
+ */
void (*detach)(struct dma_buf *, struct dma_buf_attachment *);
- /* For {map,unmap}_dma_buf below, any specific buffer attributes
- * required should get added to device_dma_parameters accessible
- * via dev->dma_params.
+ /**
+ * @map_dma_buf:
+ *
+ * This is called by dma_buf_map_attachment() and is used to map a
+ * shared &dma_buf into device address space, and it is mandatory. It
+ * can only be called if @attach has been called successfully. This
+ * essentially pins the DMA buffer into place, and it cannot be moved
+ * any more
+ *
+ * This call may sleep, e.g. when the backing storage first needs to be
+ * allocated, or moved to a location suitable for all currently attached
+ * devices.
+ *
+ * Note that any specific buffer attributes required for this function
+ * should get added to device_dma_parameters accessible via
+ * device->dma_params from the &dma_buf_attachment. The @attach callback
+ * should also check these constraints.
+ *
+ * If this is being called for the first time, the exporter can now
+ * choose to scan through the list of attachments for this buffer,
+ * collate the requirements of the attached devices, and choose an
+ * appropriate backing storage for the buffer.
+ *
+ * Based on enum dma_data_direction, it might be possible to have
+ * multiple users accessing at the same time (for reading, maybe), or
+ * any other kind of sharing that the exporter might wish to make
+ * available to buffer-users.
+ *
+ * Returns:
+ *
+ * A &sg_table scatter list of or the backing storage of the DMA buffer,
+ * already mapped into the device address space of the &device attached
+ * with the provided &dma_buf_attachment.
+ *
+ * On failure, returns a negative error value wrapped into a pointer.
+ * May also return -EINTR when a signal was received while being
+ * blocked.
*/
struct sg_table * (*map_dma_buf)(struct dma_buf_attachment *,
- enum dma_data_direction);
+ enum dma_data_direction);
+ /**
+ * @unmap_dma_buf:
+ *
+ * This is called by dma_buf_unmap_attachment() and should unmap and
+ * release the &sg_table allocated in @map_dma_buf, and it is mandatory.
+ * It should also unpin the backing storage if this is the last mapping
+ * of the DMA buffer, it the exporter supports backing storage
+ * migration.
+ */
void (*unmap_dma_buf)(struct dma_buf_attachment *,
- struct sg_table *,
- enum dma_data_direction);
+ struct sg_table *,
+ enum dma_data_direction);
+
/* TODO: Add try_map_dma_buf version, to return immed with -EBUSY
* if the call would block.
*/
- /* after final dma_buf_put() */
+ /**
+ * @release:
+ *
+ * Called after the last dma_buf_put to release the &dma_buf, and
+ * mandatory.
+ */
void (*release)(struct dma_buf *);
int (*begin_cpu_access)(struct dma_buf *, enum dma_data_direction);
* @poll: for userspace poll support
* @cb_excl: for userspace poll support
* @cb_shared: for userspace poll support
+ *
+ * This represents a shared buffer, created by calling dma_buf_export(). The
+ * userspace representation is a normal file descriptor, which can be created by
+ * calling dma_buf_fd().
+ *
+ * Shared dma buffers are reference counted using dma_buf_put() and
+ * get_dma_buf().
+ *
+ * Device DMA access is handled by the separate struct &dma_buf_attachment.
*/
struct dma_buf {
size_t size;
wait_queue_head_t poll;
struct dma_buf_poll_cb_t {
- struct fence_cb cb;
+ struct dma_fence_cb cb;
wait_queue_head_t *poll;
unsigned long active;
* This structure holds the attachment information between the dma_buf buffer
* and its user device(s). The list contains one attachment struct per device
* attached to the buffer.
+ *
+ * An attachment is created by calling dma_buf_attach(), and released again by
+ * calling dma_buf_detach(). The DMA mapping itself needed to initiate a
+ * transfer is created by dma_buf_map_attachment() and freed again by calling
+ * dma_buf_unmap_attachment().
*/
struct dma_buf_attachment {
struct dma_buf *dmabuf;
};
/**
- * helper macro for exporters; zeros and fills in most common values
- *
+ * DEFINE_DMA_BUF_EXPORT_INFO - helper macro for exporters
* @name: export-info name
+ *
+ * DEFINE_DMA_BUF_EXPORT_INFO macro defines the struct &dma_buf_export_info,
+ * zeroes it out and pre-populates exp_name in it.
*/
#define DEFINE_DMA_BUF_EXPORT_INFO(name) \
struct dma_buf_export_info name = { .exp_name = KBUILD_MODNAME, \
projects / mirror_ubuntu-bionic-kernel.git / blobdiff