dumb BOs and prime

[Rob Herring]

On Fri, Dec 4, 2015 at 12:40 PM, Benjamin Gaignard
<benjamin.gaignard at linaro.org> wrote:
> Hi Rob,
>
> I got the same problem today with sti drm/kms driver and dumb Bo.
> The issue comes become hwcomposer because is the master and authenticated on
> /dev/dri/cardX
> Dumb allocation is done by gralloc which does a new open (so it is not
> authenticated) on drm node the consequence is that we can't use prime
> functions...
> If you use render node you won't be able to call dumb functions.
>
> To get out of this I think I will implement additional helpers in gem_cma to
> have ioctl like DRM_GEM_CMA_CREATE and DRM_GEM_CMA_MMAP
> and call them instead of dumb so be able to use render node.
> Of course it is only for drivers which already use gem_cma helpers (like
> sti)

That's only marginally better than per driver BO calls which is the
whole thing I'm trying to avoid. There should be some way to pass the
auth token to gralloc?

Rob

>
> Benjamin
>
>
> Le vendredi 4 décembre 2015, Martin Peres <martin.peres at linux.intel.com> a
> écrit :
>>
>> On 04/12/15 19:49, Rob Herring wrote:
>>>
>>> I'm working on getting Android working with DRM drivers. ATM, I'm
>>> using virtio-gpu as the driver and trying to get just KMS side working
>>> without rendering. I have it working with stock AOSP and the emulated
>>> fb with a few additions to the virtio-gpu driver[1]. Now I'm trying to
>>> get things working with native KMS using drm_gralloc and
>>> drm_hwcomposer (now in AOSP). I've hit one problem though which I'm
>>> not sure how to solve without hacking around it.
>>>
>>> Is prime allowed on dumb BOs? AIUI, dumb buffer allocation is not
>>> allowed on render nodes and drmPrimeHandleToFD is not allowed on
>>> card0, so I'm stuck. I could open both nodes, but then I want the case
>>> of no render node to work. After some searching, I thought it was a
>>> matter of needing to do drmAuthMagic, but then found that is
>>> considered obsolete[2].
>>
>>
>> Obsolete when using render nodes, but still necessary on usual nodes
>> (/dev/dri/cardX) as far as I remember. The usual nodes can do everything the
>> render nodes can do.
>>
>> Authentication should help! Please make sure you are master or
>> authenticated before doing anything on the usual nodes.
>>
>>>
>>> Rob
>>>
>>> [1] git://git.kernel.org/pub/scm/linux/kernel/git/robh/linux.git
>>> android-4.4
>>> [2]
>>> http://www.x.org/wiki/Events/XDC2013/XDC2013DavidHerrmannDRMSecurity/slides.pdf
>>> _______________________________________________
>>> dri-devel mailing list
>>> dri-devel at lists.freedesktop.org
>>> http://lists.freedesktop.org/mailman/listinfo/dri-devel
>>>
>
>
> --
>
> Benjamin Gaignard
>
> Graphic Working Group
>
> Linaro.org │ Open source software for ARM SoCs
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