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| author | Christopher James Halse Rogers <christopher.halse.rogers@canonical.com> | 2013-09-10 08:06:45 +0200 |
|---|---|---|
| committer | Sumit Semwal <sumit.semwal@linaro.org> | 2013-09-10 08:06:45 +0200 |
| commit | 19e8697ba45e7bcdb04f2adf6110fbf4882863e5 (patch) | |
| tree | 249547a50a16d33e2c3c2dea96a592b2b823dc2b /drivers/base | |
| parent | dma-buf: Check return value of anon_inode_getfile (diff) | |
| download | linux-19e8697ba45e7bcdb04f2adf6110fbf4882863e5.tar.xz linux-19e8697ba45e7bcdb04f2adf6110fbf4882863e5.zip | |
dma-buf: Expose buffer size to userspace (v2)
Each dma-buf has an associated size and it's reasonable for userspace
to want to know what it is.
Since userspace already has an fd, expose the size using the
size = lseek(fd, SEEK_END, 0); lseek(fd, SEEK_CUR, 0);
idiom.
v2: Added Daniel's sugeested documentation, with minor fixups
Signed-off-by: Christopher James Halse Rogers <christopher.halse.rogers@canonical.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Tested-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Sumit Semwal <sumit.semwal@linaro.org>
Diffstat (limited to 'drivers/base')
| -rw-r--r-- | drivers/base/dma-buf.c | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/drivers/base/dma-buf.c b/drivers/base/dma-buf.c index 2d5ac1a1842e..1e16cbd61da2 100644 --- a/drivers/base/dma-buf.c +++ b/drivers/base/dma-buf.c @@ -77,9 +77,36 @@ static int dma_buf_mmap_internal(struct file *file, struct vm_area_struct *vma) return dmabuf->ops->mmap(dmabuf, vma); } +static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence) +{ + struct dma_buf *dmabuf; + loff_t base; + + if (!is_dma_buf_file(file)) + return -EBADF; + + dmabuf = file->private_data; + + /* only support discovering the end of the buffer, + but also allow SEEK_SET to maintain the idiomatic + SEEK_END(0), SEEK_CUR(0) pattern */ + if (whence == SEEK_END) + base = dmabuf->size; + else if (whence == SEEK_SET) + base = 0; + else + return -EINVAL; + + if (offset != 0) + return -EINVAL; + + return base + offset; +} + static const struct file_operations dma_buf_fops = { .release = dma_buf_release, .mmap = dma_buf_mmap_internal, + .llseek = dma_buf_llseek, }; /* @@ -137,6 +164,8 @@ struct dma_buf *dma_buf_export_named(void *priv, const struct dma_buf_ops *ops, kfree(dmabuf); return ERR_CAST(file); } + + file->f_mode |= FMODE_LSEEK; dmabuf->file = file; mutex_init(&dmabuf->lock); |