[PATCH 2/4] dma-buf: Add ioctls to allow userspace to flush

[Sumit Semwal]

Hi Tiago,

Thanks for the patch!

On 12 August 2015 at 02:29, Tiago Vignatti <tiago.vignatti at intel.com> wrote:
> From: Daniel Vetter <daniel.vetter at ffwll.ch>
>
> FIXME: Update kerneldoc for begin/end to make it clear that those are
> for mmap too.

I think if we're going to add this patch upstream, atleast the FIXMEs
should be fixed.
>
> Open: Do we need a special indication that the begin/end is from
> userspace mmap and not from kernel mmap?
>
> There's also the question already about kernel internal users - vmap
> and kmap interfaces are much different ... We might need to add a
> mapping enum to the begin/end dma-buf functions.

Also, this looks like another thing that could be added right now
while we're adding this change.
>
> v2 (Tiago): Fix header file type names (u64 -> __u64)
>
> Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
> Signed-off-by: Tiago Vignatti <tiago.vignatti at intel.com>
> ---
>  drivers/dma-buf/dma-buf.c    | 47 ++++++++++++++++++++++++++++++++++++++++++++
>  include/uapi/linux/dma-buf.h | 39 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 86 insertions(+)
>  create mode 100644 include/uapi/linux/dma-buf.h
>
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 155c146..4820d61 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -34,6 +34,8 @@
>  #include <linux/poll.h>
>  #include <linux/reservation.h>
>
> +#include <uapi/linux/dma-buf.h>
> +
>  static inline int is_dma_buf_file(struct file *);
>
>  struct dma_buf_list {
> @@ -251,11 +253,56 @@ out:
>         return events;
>  }
>
> +static long dma_buf_ioctl(struct file *file,
> +                         unsigned int cmd, unsigned long arg)
> +{
> +       struct dma_buf *dmabuf;
> +       struct dma_buf_sync sync;
> +       enum dma_data_direction direction;
> +
> +       dmabuf = file->private_data;
> +
> +       if (!is_dma_buf_file(file))
> +               return -EINVAL;
> +
> +       switch (cmd) {
> +       case DMA_BUF_IOCTL_SYNC:
> +               if (copy_from_user(&sync, (void __user *) arg, sizeof(sync)))
> +                       return -EFAULT;
> +
> +               if (sync.flags & DMA_BUF_SYNC_RW)
> +                       direction = DMA_BIDIRECTIONAL;
> +               else if (sync.flags & DMA_BUF_SYNC_READ)
> +                       direction = DMA_FROM_DEVICE;
> +               else if (sync.flags & DMA_BUF_SYNC_WRITE)
> +                       direction = DMA_TO_DEVICE;
> +               else
> +                       return -EINVAL;
> +
> +               if (sync.flags & ~DMA_BUF_SYNC_VALID_FLAGS_MASK)
> +                       return -EINVAL;
> +
> +               /* FIXME: Check for overflows in start/length. */
> +
Even this for fixing in this patch itself.

> +               if (sync.flags & DMA_BUF_SYNC_END)
> +                       dma_buf_end_cpu_access(dmabuf, sync.start,
> +                                              sync.length, direction);
> +               else
> +                       dma_buf_begin_cpu_access(dmabuf, sync.start,
> +                                                sync.length, direction);
> +
> +               return 0;
> +       default:
> +               return -ENOTTY;
> +       }
> +}
> +
>  static const struct file_operations dma_buf_fops = {
>         .release        = dma_buf_release,
>         .mmap           = dma_buf_mmap_internal,
>         .llseek         = dma_buf_llseek,
>         .poll           = dma_buf_poll,
> +       .unlocked_ioctl = dma_buf_ioctl,
>  };
>
>  /*
> diff --git a/include/uapi/linux/dma-buf.h b/include/uapi/linux/dma-buf.h
> new file mode 100644
> index 0000000..e5327df
> --- /dev/null
> +++ b/include/uapi/linux/dma-buf.h
> @@ -0,0 +1,39 @@
> +/*
> + * Framework for buffer objects that can be shared across devices/subsystems.
> + *
> + * Copyright(C) 2015 Intel Ltd
> + *
> + * This program is free software; you can redistribute it and/or modify it
> + * under the terms of the GNU General Public License version 2 as published by
> + * the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful, but WITHOUT
> + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
> + * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
> + * more details.
> + *
> + * You should have received a copy of the GNU General Public License along with
> + * this program.  If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#ifndef _DMA_BUF_UAPI_H_
> +#define _DMA_BUF_UAPI_H_
> +
> +struct dma_buf_sync {
> +       __u64 flags;
> +       __u64 start;
> +       __u64 length;
> +};
> +
> +#define DMA_BUF_SYNC_READ      (1 << 0)
> +#define DMA_BUF_SYNC_WRITE     (2 << 0)
> +#define DMA_BUF_SYNC_RW                (3 << 0)
> +#define DMA_BUF_SYNC_START     (0 << 2)
> +#define DMA_BUF_SYNC_END       (1 << 2)
> +#define DMA_BUF_SYNC_VALID_FLAGS_MASK \
> +       (DMA_BUF_SYNC_RW | DMA_BUF_SYNC_END)
> +
> +#define DMA_BUF_BASE           'b'
> +#define DMA_BUF_IOCTL_SYNC     _IOWR(DMA_BUF_BASE, 0, struct dma_buf_sync)
> +
> +#endif
> --
> 2.1.0
>
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-- 
Thanks and regards,
Sumit Semwal.