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dma-buf: Implement DMA_BUF_IOCTL_{EXPORT,IMPORT}_SYNC_FILE #405

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dma-buf: Implement DMA_BUF_IOCTL_{EXPORT,IMPORT}_SYNC_FILE #405

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c3e1d03
dma-buf: Add necessary flags for ioctls on DMA-BUF files
obiwac Jan 15, 2026
011daab
dma-buf: Implement `DMA_BUF_IOCTL_{EXPORT,IMPORT}_SYNC_FILE`
obiwac Jan 15, 2026
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83 changes: 81 additions & 2 deletions drivers/dma-buf/dma-buf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -51,7 +51,9 @@ __FBSDID("$FreeBSD$");

#include <linux/list.h>
#include <linux/dma-buf.h>
#include <linux/dma-fence-unwrap.h>
#include <linux/dma-resv.h>
#include <linux/sync_file.h>

#include <uapi/linux/dma-buf.h>

Expand Down Expand Up @@ -225,6 +227,78 @@ dma_buf_end_cpu_access(struct dma_buf *db, enum dma_data_direction dir)
return (0);
}

static int
dma_buf_export_sync_file(struct dma_buf *db, struct thread *td,
struct dma_buf_export_sync_file *export_sync_file)
{
int usage = dma_resv_usage_rw(export_sync_file->flags & DMA_BUF_SYNC_WRITE);
int fd, rc;
struct dma_fence *fence;
struct sync_file *sync_file;
struct file *file;

rc = dma_resv_get_singleton(db->resv, usage, &fence);
if (rc != 0)
return (rc);
if (fence == NULL)
return (-ENXIO);

sync_file = sync_file_create(fence);
if (sync_file == NULL)
return (-ENOMEM);

rc = falloc(td, &file, &fd, O_CLOEXEC);
if (rc != 0)
return (-rc);

sync_file->linux_file->_file = file;

/* We need to set these for linux_fget to work in sync_file_fdget. */
sync_file->linux_file->_file->f_ops = &linuxfileops;
sync_file->linux_file->_file->f_data = sync_file->linux_file;

/* Transfer reference count from Linux file to BSD file (cf fd_install). */
while (refcount_release(&sync_file->linux_file->f_count) == 0)
refcount_acquire(&file->f_count);
fput(sync_file->linux_file);

export_sync_file->fd = fd;
dma_fence_put(fence);

return (0);
}

static int
dma_buf_import_sync_file(struct dma_buf *db,
struct dma_buf_import_sync_file *import_sync_file)
{
int usage = dma_resv_usage_rw(import_sync_file->flags & DMA_BUF_SYNC_WRITE);
int rc = 0;
size_t fence_count = 0;
struct dma_fence_unwrap cursor;
struct dma_fence *f, *fence;

fence = sync_file_get_fence(import_sync_file->fd);
if (fence == NULL)
return (-EINVAL);

dma_fence_unwrap_for_each(f, &cursor, fence)
fence_count++;

dma_resv_lock(db->resv, NULL);

rc = dma_resv_reserve_fences(db->resv, fence_count);
if (rc != 0)
goto out;
dma_fence_unwrap_for_each(f, &cursor, fence)
dma_resv_add_fence(db->resv, f, usage);

out:
dma_resv_unlock(db->resv);
dma_fence_put(fence);
return (rc);
}

static int
dma_buf_ioctl(struct file *fp, u_long com, void *data,
struct ucred *active_cred, struct thread *td)
Expand All @@ -238,11 +312,12 @@ dma_buf_ioctl(struct file *fp, u_long com, void *data,
return (EINVAL);

db = fp->f_data;
sync = data;
rc = 0;

switch (com) {
case DMA_BUF_IOCTL_SYNC:
sync = data;

if (sync->flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
return (EINVAL);

Expand All @@ -264,6 +339,10 @@ dma_buf_ioctl(struct file *fp, u_long com, void *data,
else
rc = dma_buf_begin_cpu_access(db, dir);
return (-rc);
case DMA_BUF_IOCTL_EXPORT_SYNC_FILE:
return (-dma_buf_export_sync_file(db, td, data));
case DMA_BUF_IOCTL_IMPORT_SYNC_FILE:
return (-dma_buf_import_sync_file(db, data));
default:
return (ENOTTY);
}
Expand Down Expand Up @@ -465,7 +544,7 @@ dma_buf_export(const struct dma_buf_export_info *exp_info)
if ((err = falloc_noinstall(curthread, &fp)) != 0)
goto err;

finit(fp, 0, DTYPE_DMABUF, db, &dma_buf_fileops);
finit(fp, FREAD | FWRITE, DTYPE_DMABUF, db, &dma_buf_fileops);

db->linux_file = fp;
mutex_init(&db->lock);
Expand Down
14 changes: 14 additions & 0 deletions linuxkpi/bsd/include/uapi/linux/dma-buf.h
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Original file line number Diff line number Diff line change
Expand Up @@ -42,4 +42,18 @@ struct dma_buf_sync {

#define DMA_BUF_IOCTL_SYNC _IOW('b', 0, struct dma_buf_sync)

struct dma_buf_export_sync_file {
__u32 flags;
__s32 fd;
};

#define DMA_BUF_IOCTL_EXPORT_SYNC_FILE _IOWR('b', 1, struct dma_buf_export_sync_file)

struct dma_buf_import_sync_file {
__u32 flags;
__s32 fd;
};

#define DMA_BUF_IOCTL_IMPORT_SYNC_FILE _IOW('b', 2, struct dma_buf_import_sync_file)

#endif /* _BSD_LKPI_UAPI_LINUX_DMA_BUF_H_ */