diff mbox series

[v2,04/21] v4l: add documentation for secure memory flag

Message ID 20231106120423.23364-5-yunfei.dong@mediatek.com
State New
Headers
Series add driver to support secure video decoder |

Commit Message

Yunfei Dong (董云飞) Nov. 6, 2023, 12:04 p.m. UTC 
  From: Jeffrey Kardatzke <jkardatzke@google.com>

Adds documentation for V4L2_MEMORY_FLAG_SECURE.

Signed-off-by: Jeffrey Kardatzke <jkardatzke@google.com>
Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com>
---
 Documentation/userspace-api/media/v4l/buffer.rst | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

Comments

Pavel Machek Nov. 11, 2023, 7:06 p.m. UTC | #1 
Hi!

> From: Jeffrey Kardatzke <jkardatzke@google.com>
> 
> Adds documentation for V4L2_MEMORY_FLAG_SECURE.

> --- a/Documentation/userspace-api/media/v4l/buffer.rst
> +++ b/Documentation/userspace-api/media/v4l/buffer.rst
> @@ -696,7 +696,7 @@ enum v4l2_memory
>  
>  .. _memory-flags:
>  
> -Memory Consistency Flags
> +Memory Flags
>  ------------------------
>  
>  .. raw:: latex
> @@ -728,6 +728,12 @@ Memory Consistency Flags
>  	only if the buffer is used for :ref:`memory mapping <mmap>` I/O and the
>  	queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS
>  	<V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.
> +    * .. _`V4L2-MEMORY-FLAG-SECURE`:
> +
> +      - ``V4L2_MEMORY_FLAG_SECURE``
> +      - 0x00000002
> +      - DMA bufs passed into the queue will be validated to ensure they were
> +	allocated from a secure dma-heap.

Could we get some more information somewhere? Why would userspace want
to work with "secure" DMA heaps? How exactly are they different from
others? What attacks are these secure against? What is goal of all
this? DRM?

BR,
								Pavel
Jeffrey Kardatzke Nov. 13, 2023, 6:04 p.m. UTC | #2 
Mediatek,

What happened to the RFC cover letter that explained more overall for
what this is for?  That should be included in the 0th patch for each
of the series.

Pavel,
This is for secure video playback where the memory is 'secure'
(TrustZone in this case) and is only accessible in the TEE and
specific HW blocks. Userspace has FDs that reference the memory, but
kernel/userspace can't actually map/access that memory.  And yes, this
is for supporting DRM (Digital Rights Management) playback.

Cheers,
Jeff


On Sat, Nov 11, 2023 at 11:06 AM Pavel Machek <pavel@ucw.cz> wrote:
>
> Hi!
>
> > From: Jeffrey Kardatzke <jkardatzke@google.com>
> >
> > Adds documentation for V4L2_MEMORY_FLAG_SECURE.
>
> > --- a/Documentation/userspace-api/media/v4l/buffer.rst
> > +++ b/Documentation/userspace-api/media/v4l/buffer.rst
> > @@ -696,7 +696,7 @@ enum v4l2_memory
> >
> >  .. _memory-flags:
> >
> > -Memory Consistency Flags
> > +Memory Flags
> >  ------------------------
> >
> >  .. raw:: latex
> > @@ -728,6 +728,12 @@ Memory Consistency Flags
> >       only if the buffer is used for :ref:`memory mapping <mmap>` I/O and the
> >       queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS
> >       <V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.
> > +    * .. _`V4L2-MEMORY-FLAG-SECURE`:
> > +
> > +      - ``V4L2_MEMORY_FLAG_SECURE``
> > +      - 0x00000002
> > +      - DMA bufs passed into the queue will be validated to ensure they were
> > +     allocated from a secure dma-heap.
>
> Could we get some more information somewhere? Why would userspace want
> to work with "secure" DMA heaps? How exactly are they different from
> others? What attacks are these secure against? What is goal of all
> this? DRM?
>
> BR,
>                                                                 Pavel
> --
> People of Russia, stop Putin before his war on Ukraine escalates.
diff mbox series

Patch

diff --git a/Documentation/userspace-api/media/v4l/buffer.rst b/Documentation/userspace-api/media/v4l/buffer.rst
index 52bbee81c080..a5a7d1c72d53 100644
--- a/Documentation/userspace-api/media/v4l/buffer.rst
+++ b/Documentation/userspace-api/media/v4l/buffer.rst
@@ -696,7 +696,7 @@  enum v4l2_memory
 
 .. _memory-flags:
 
-Memory Consistency Flags
+Memory Flags
 ------------------------
 
 .. raw:: latex
@@ -728,6 +728,12 @@  Memory Consistency Flags
 	only if the buffer is used for :ref:`memory mapping <mmap>` I/O and the
 	queue reports the :ref:`V4L2_BUF_CAP_SUPPORTS_MMAP_CACHE_HINTS
 	<V4L2-BUF-CAP-SUPPORTS-MMAP-CACHE-HINTS>` capability.
+    * .. _`V4L2-MEMORY-FLAG-SECURE`:
+
+      - ``V4L2_MEMORY_FLAG_SECURE``
+      - 0x00000002
+      - DMA bufs passed into the queue will be validated to ensure they were
+	allocated from a secure dma-heap.
 
 .. raw:: latex