dma-buf: Add ioctls to allow userspace to flush

The userspace might need some sort of cache coherency management e.g. when CPU
and GPU domains are being accessed through dma-buf at the same time. To
circumvent this problem there are begin/end coherency markers, that forward
directly to existing dma-buf device drivers vfunc hooks. Userspace can make use
of those markers through the DMA_BUF_IOCTL_SYNC ioctl. The sequence would be
used like following:
     - mmap dma-buf fd
     - for each drawing/upload cycle in CPU 1. SYNC_START ioctl, 2. read/write
       to mmap area 3. SYNC_END ioctl. This can be repeated as often as you
       want (with the new data being consumed by the GPU or say scanout device)
     - munmap once you don't need the buffer any more

v2 (Tiago): Fix header file type names (u64 -> __u64)
v3 (Tiago): Add documentation. Use enum dma_buf_sync_flags to the begin/end
dma-buf functions. Check for overflows in start/length.
v4 (Tiago): use 2d regions for sync.
v5 (Tiago): forget about 2d regions (v4); use _IOW in DMA_BUF_IOCTL_SYNC and
remove range information from struct dma_buf_sync.
v6 (Tiago): use __u64 structured padded flags instead enum. Adjust
documentation about the recommendation on using sync ioctls.
v7 (Tiago): Alex' nit on flags definition and being even more wording in the
doc about sync usage.
v9 (Tiago): remove useless is_dma_buf_file check. Fix sync.flags conditionals
and its mask order check. Add <linux/types.h> include in dma-buf.h.

Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Sumit Semwal <sumit.semwal@linaro.org>
Reviewed-by: Stéphane Marchesin <marcheu@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Signed-off-by: Tiago Vignatti <tiago.vignatti@intel.com>
Reviewed-by: David Herrmann <dh.herrmann@gmail.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1455228291-29640-1-git-send-email-tiago.vignatti@intel.com

1 files changed, 45 insertions, 0 deletions

diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
index b2ac13b4ddaa..9810d1df0691 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 +253,54 @@ 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;
+
+        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_VALID_FLAGS_MASK)
+                        return -EINVAL;
+
+                switch (sync.flags & DMA_BUF_SYNC_RW) {
+                case DMA_BUF_SYNC_READ:
+                        direction = DMA_FROM_DEVICE;
+                        break;
+                case DMA_BUF_SYNC_WRITE:
+                        direction = DMA_TO_DEVICE;
+                        break;
+                case DMA_BUF_SYNC_RW:
+                        direction = DMA_BIDIRECTIONAL;
+                        break;
+                default:
+                        return -EINVAL;
+                }
+
+                if (sync.flags & DMA_BUF_SYNC_END)
+                        dma_buf_end_cpu_access(dmabuf, direction);
+                else
+                        dma_buf_begin_cpu_access(dmabuf, 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,
 };
 
 /*