[PATCH] drm: kms_helper: don't lose hotplug event

Chris Wilson chris at chris-wilson.co.uk
Thu Oct 25 02:07:46 PDT 2012

On Wed, 24 Oct 2012 21:16:53 +0200, Daniel Vetter <daniel.vetter at ffwll.ch> wrote:
> There's a race window (small for hpd, 10s large for polled outputs)
> where userspace could sneak in with an unrelated connnector probe
> ioctl call and eat the hotplug event (since neither the hpd nor the
> poll code see a state change).
> To avoid this, check whether the connector state changes in all other
> ->detect calls (in the current helper code that's only probe_single)
> and if that's the case, fire off a hotplug event. Note that we can't
> directly call the hotplug event handler, since that expects that no
> locks are held (due to reentrancy with the fb code to update the kms
> console).
> Also, this requires that drivers using the probe_single helper
> function set up the poll work. All current drivers do that already,
> and with the reworked hpd handling there'll be no downside to
> unconditionally setting up the poll work any more.
> Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>

Aye, we do want the hotplug notification for the desktop to respond to
if the user happens to steal it by haplessly querying the system with
xrandr. lgtm,

Reviewed-by: Chris Wilson <chris at chris-wilson.co.uk>

Chris Wilson, Intel Open Source Technology Centre

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