linux-kernel - Re: [PATCH v2] imx-drm: Fix probe failure

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Message-ID: <20130829183706.GZ30088@pengutronix.de>
Date:	Thu, 29 Aug 2013 20:37:06 +0200
From:	Sascha Hauer <s.hauer@...gutronix.de>
To:	Fabio Estevam <festevam@...il.com>
Cc:	Fabio Estevam <fabio.estevam@...escale.com>,
	Dave Airlie <airlied@...hat.com>, daniel.vetter@...ll.ch,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] imx-drm: Fix probe failure

On Thu, Aug 29, 2013 at 03:30:12PM -0300, Fabio Estevam wrote:
> >> @@ -485,11 +480,6 @@ int imx_drm_add_crtc(struct drm_crtc *crtc,
> >>
> >>       mutex_lock(&imxdrm->mutex);
> >>
> >> -     if (imxdrm->references) {
> >> -             ret = -EBUSY;
> >> -             goto err_busy;
> >> -     }
> >
> > As I told in v1: Simply removing the code is not an option. We agreed
> > that we use the drm core reference counting, so you must actually test
> > for it here...
> 
> Yes, we did, but after reading a separate thread on this topic, I
> learned that drm core does not support it currently.
> 
> Daniel mentions [1]: "And I wouldn't worry about module unloading and
> refcounting for
> now since core drm is terminally broken in that area already anyway"
> 
> [1] http://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg43698.html
> 
> Can't we just apply this patch so that imx-drm can be functional again
> and fix module unloading/refcount later?

It's not about the module refcount. It's only that a on a drm device
which is in use you better do not add/remove components.

Again: The imx-drm driver does *not* do hotplugging. It will *not* add
or remove components when the device is opened. The code you remove
exactly makes (or made before Daniels patch) that sure.

Sascha

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