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| author | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-12 04:09:14 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2013-09-12 04:09:14 +0200 |
| commit | b3b7568490bb66688ee64f4ab72ec697f4f983c5 (patch) | |
| tree | e55098d4c05d2169e1934dcdf816e476c2af86f8 /Documentation | |
| parent | Merge branch 'akpm' (patches from Andrew Morton) (diff) | |
| parent | dma-buf: Expose buffer size to userspace (v2) (diff) | |
| download | linux-b3b7568490bb66688ee64f4ab72ec697f4f983c5.tar.xz linux-b3b7568490bb66688ee64f4ab72ec697f4f983c5.zip | |
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
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/dma-buf-sharing.txt | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/dma-buf-sharing.txt b/Documentation/dma-buf-sharing.txt index e31a2a9d2b07..505e71172ae7 100644 --- a/Documentation/dma-buf-sharing.txt +++ b/Documentation/dma-buf-sharing.txt @@ -407,6 +407,18 @@ Being able to mmap an export dma-buf buffer object has 2 main use-cases: interesting ways depending upong the exporter (if userspace starts depending upon this implicit synchronization). +Other Interfaces Exposed to Userspace on the dma-buf FD +------------------------------------------------------ + +- Since kernel 3.12 the dma-buf FD supports the llseek system call, but only + with offset=0 and whence=SEEK_END|SEEK_SET. SEEK_SET is supported to allow + the usual size discover pattern size = SEEK_END(0); SEEK_SET(0). Every other + llseek operation will report -EINVAL. + + If llseek on dma-buf FDs isn't support the kernel will report -ESPIPE for all + cases. Userspace can use this to detect support for discovering the dma-buf + size using llseek. + Miscellaneous notes ------------------- |