[Intel-gfx] [PATCH] drm/i915: intel_audio clear eld buf when disconnecting monitor

[Yang, Libin]

> -----Original Message-----
> From: Takashi Iwai [mailto:tiwai at suse.de]
> Sent: Monday, March 21, 2016 6:45 PM
> To: libin.yang at linux.intel.com
> Cc: intel-gfx at lists.freedesktop.org; conselvan2 at gmail.com;
> jani.nikula at linux.intel.com; ville.syrjala at linux.intel.com; Vetter, Daniel;
> tiwai at suse.de; Yang, Libin
> Subject: Re: [PATCH] drm/i915: intel_audio clear eld buf when
> disconnecting monitor
> 
> On Mon, 21 Mar 2016 06:03:29 +0100,
> libin.yang at linux.intel.com wrote:
> >
> > From: Libin Yang <libin.yang at linux.intel.com>
> >
> > When disconnecting monitor, dev_priv->dig_port_map[port]
> > will be set NULL, which causes eld will not be updated in
> > i915_audio_component_get_eld().
> >
> > This patch clears the eld buf when dev_priv->dig_port_map[port]
> > is NULL.
> >
> > Signed-off-by: Libin Yang <libin.yang at linux.intel.com>
> 
> While this isn't certainly bad, I don't think it's mandatory.  The
> function returns zero, i.e. no data is copied.  So the caller
> shouldn't expect that the buffer is cleared in this case.

Without the patch, we find when unplug the monitor, the eld info
will not be updated. The means the eld info in the procfs still remains
the old info after the monitor is disconnected.

> 
> Actually, if we do zero-clear, a safer fix would be to do it at the
> beginning.  The similar "leak" can be seen, as we do memcpy() only for
> drm_eld_size() bytes at max.

OK. I will clear at the beginning.

> 
> 
> thanks,
> 
> Takashi
> 
> > ---
> >  drivers/gpu/drm/i915/intel_audio.c | 7 +++++++
> >  1 file changed, 7 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/i915/intel_audio.c
> b/drivers/gpu/drm/i915/intel_audio.c
> > index fdc8b2a..9d3879e 100644
> > --- a/drivers/gpu/drm/i915/intel_audio.c
> > +++ b/drivers/gpu/drm/i915/intel_audio.c
> > @@ -732,6 +732,13 @@ static int
> i915_audio_component_get_eld(struct device *dev, int port,
> >  			ret = drm_eld_size(eld);
> >  			memcpy(buf, eld, min(max_bytes, ret));
> >  		}
> > +	} else {
> > +		/* dev_priv->dig_port_map[port] will be set NULL in
> > +		 * intel_audio_codec_disable when disconnecting
> monitor.
> > +		 * We need clear the eld buf.
> > +		 */
> > +		memset(buf, 0, max_bytes);
> > +		ret = 0;
> >  	}
> >
> >  	mutex_unlock(&dev_priv->av_mutex);
> > --
> > 1.9.1
> >