linux-kernel - Re: [PATCH v5 2/6] drm/bridge: Add a devm

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Message-ID: <1610977.GUN5zSZ7yI@avalon>
Date:   Sat, 05 Aug 2017 00:25:08 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Eric Anholt <eric@...olt.net>
Cc:     dri-devel@...ts.freedesktop.org,
        Archit Taneja <architt@...eaurora.org>,
        Andrzej Hajda <a.hajda@...sung.com>,
        Thierry Reding <thierry.reding@...il.com>,
        linux-kernel@...r.kernel.org, Daniel Vetter <daniel.vetter@...l.ch>
Subject: Re: [PATCH v5 2/6] drm/bridge: Add a devm_ allocator for panel bridge.

Hi Eric,

On Friday 04 Aug 2017 13:43:25 Eric Anholt wrote:
> Laurent Pinchart <laurent.pinchart@...asonboard.com> writes:
> > On Tuesday 18 Jul 2017 14:05:06 Eric Anholt wrote:
> >> This will let drivers reduce the error cleanup they need, in
> >> particular the "is_panel_bridge" flag.
> >> 
> >> v2: Slight cleanup of remove function by Andrzej
> > 
> > I just want to point out that, in the context of Daniel's work on
> > hot-unplug, 90% of the devm_* allocations are wrong and will get in the
> > way. All DRM core objects that are accessible one way or another from
> > userspace will need to be properly reference-counted and freed only when
> > the last reference disappears, which could be well after the
> > corresponding device is removed. I believe this could be one such objects
> > :-/
> 
> Sure, if you're hotplugging, your life is pain.  For non-hotpluggable
> devices, like our SOC platform devices (current panel-bridge consumers),
> this still seems like an excellent simplification of memory management.

It encourages driver writers to write code that they will have to fix later. 
That's certainly a simplification, but certainly not a good thing in my 
opinion :-)

-- 
Regards,

Laurent Pinchart