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Commit b3b7568490bb66688ee64f4ab72ec697f4f983c5

Authored by Linus Torvalds
2 parents c2d95729e3 19e8697ba4
Exists in smarc-imx_3.14.28_1.0.0_ga and in 1 other branch imx_3.14.28_1.0.0_ga

Merge tag 'for-3.12' of git://git.linaro.org/people/sumitsemwal/linux-dma-buf 

Pull dma-buf updates from Sumit Semwal:
 "Yet another small one - dma-buf framework now supports size discovery
  of the buffer via llseek"

* tag 'for-3.12' of git://git.linaro.org/people/sumitsemwal/linux-dma-buf:
  dma-buf: Expose buffer size to userspace (v2)
  dma-buf: Check return value of anon_inode_getfile

Showing 2 changed files Side-by-side Diff

Documentation/dma-buf-sharing.txt
Diff comments   View file @ b3b7568
... ... @@ -407,6 +407,18 @@
407 407 interesting ways depending upong the exporter (if userspace starts depending
408 408 upon this implicit synchronization).
409 409  
  410 +Other Interfaces Exposed to Userspace on the dma-buf FD
  411 +------------------------------------------------------
  412 +
  413 +- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only
  414 + with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow
  415 + the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other
  416 + llseek operation will report -EINVAL.
  417 +
  418 + If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all
  419 + cases. Userspace can use this to detect support for discovering the dma-buf
  420 + size using llseek.
  421 +
410 422 Miscellaneous notes
411 423 -------------------
412 424  
drivers/base/dma-buf.c
Diff comments   View file @ b3b7568
... ... @@ -77,9 +77,36 @@
77 77 return dmabuf->ops->mmap(dmabuf, vma);
78 78 }
79 79  
  80 +static loff_t dma_buf_llseek(struct file *file, loff_t offset, int whence)
  81 +{
  82 + struct dma_buf *dmabuf;
  83 + loff_t base;
  84 +
  85 + if (!is_dma_buf_file(file))
  86 + return -EBADF;
  87 +
  88 + dmabuf = file->private_data;
  89 +
  90 + /* only support discovering the end of the buffer,
  91 + but also allow SEEK_SET to maintain the idiomatic
  92 + SEEK_END(0), SEEK_CUR(0) pattern */
  93 + if (whence == SEEK_END)
  94 + base = dmabuf->size;
  95 + else if (whence == SEEK_SET)
  96 + base = 0;
  97 + else
  98 + return -EINVAL;
  99 +
  100 + if (offset != 0)
  101 + return -EINVAL;
  102 +
  103 + return base + offset;
  104 +}
  105 +
80 106 static const struct file_operations dma_buf_fops = {
81 107 .release = dma_buf_release,
82 108 .mmap = dma_buf_mmap_internal,
  109 + .llseek = dma_buf_llseek,
83 110 };
84 111  
85 112 /*
86 113  
... ... @@ -133,7 +160,12 @@
133 160 dmabuf->exp_name = exp_name;
134 161  
135 162 file = anon_inode_getfile("dmabuf", &dma_buf_fops, dmabuf, flags);
  163 + if (IS_ERR(file)) {
  164 + kfree(dmabuf);
  165 + return ERR_CAST(file);
  166 + }
136 167  
  168 + file->f_mode |= FMODE_LSEEK;
137 169 dmabuf->file = file;
138 170  
139 171 mutex_init(&dmabuf->lock);