[RFC] drm + i915 DP MST code preview

[Dave Airlie]

On 7 May 2014 17:16, Aaron Plattner <aplattner at nvidia.com> wrote:
> On 05/03/2014 02:00 AM, Chris Wilson wrote:
>>
>> On Sat, May 03, 2014 at 07:08:02AM +1000, Dave Airlie wrote:
>>>
>>> On 2 May 2014 18:52, Chris Wilson <chris at chris-wilson.co.uk> wrote:
>>>>
>>>> On Fri, May 02, 2014 at 02:39:37PM +1000, Dave Airlie wrote:
>>>
>>> the GUID is only on DP 1.2 devices, so you don't get one for ever
>>> port, also GUIDs are wiped on powerdown on most devices, default GUID
>>> is 0 except where devices have USB hubs as well, so it probably
>>> doesn't make much sense to bother exposing them directly.
>>
>>
>> Ok. It looks like if we do attempt to maintain persistent naming, we need
>> to do it in the kernel anyway. That is to make sure that a downstream
>> device always has the same type-id upon reconnection - at least for the
>> lifetime of module. Or maybe the output name is irrelevant for
>> preserving extended desktop configurations?
>
>
> Dunno if it helps, but for roughly similar reasons we ended up naming the
> outputs based on their topology paths in the NVIDIA driver.  So for example
> a port named DP-3 that has a Dell UP2414Q attached will show up as two
> outputs named DP-3.1 and DP-3.8 since its internal bridge uses downstream
> ports 1 and 8.  This has worked out fairly well in practice.
>
> Here's how I described it in the README:
>
>     When DisplayPort 1.2 branch devices are present, display
>     devices will be created with type- and connector-based names
>     that are based on how they are connected to the branch device
>     tree. For example, if a connector named DP-2 has a branch
>     device attached and a DisplayPort device is connected to the
>     branch device's first downstream port, a display device named
>     DP-2.1 might be created. If another branch device is
>     connected between the first branch device and the display
>     device, the name might be DP-2.1.1.
>
>     To avoid cluttering the output list, DisplayPort 1.2 devices
>     can be deleted when they are no longer connected and are not
>     named in any MetaModes. This behavior can be enabled with the
>     DeleteUnusedDP12Displays option.
>
> http://us.download.nvidia.com/XFree86/Linux-x86/337.19/README/displaydevicenames.html

Is the cleaning up an option because it caused some problems?

I'm seeing some gnome-settings-daemon, gnome-shell crash because the
XIDs are gone away and they get X errors, just wondering if this is
what you were seeing,

Dave.