linux-kernel - Re: [PATCH 3/5] media: sunxi: Add A10 CSI driver

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Message-ID: <20181121220102.6nn7uwu2c67zs6pz@mara.localdomain>
Date:   Thu, 22 Nov 2018 00:01:03 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Hans Verkuil <hverkuil@...all.nl>,
        Hans Verkuil <hans.verkuil@...co.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        linux-media@...r.kernel.org, Andrzej Hajda <a.hajda@...sung.com>,
        Chen-Yu Tsai <wens@...e.org>, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Subject: Re: [PATCH 3/5] media: sunxi: Add A10 CSI driver

On Thu, Nov 15, 2018 at 09:51:06PM +0100, Maxime Ripard wrote:
> Hi Hans,
> 
> Thanks for your review! I'll address the other comments you made.
> 
> On Tue, Nov 13, 2018 at 01:24:47PM +0100, Hans Verkuil wrote:
> > > +static int csi_probe(struct platform_device *pdev)
> > > +{
> > > +	struct sun4i_csi *csi;
> > > +	struct resource *res;
> > > +	int ret;
> > > +	int irq;
> > > +
> > > +	csi = devm_kzalloc(&pdev->dev, sizeof(*csi), GFP_KERNEL);
> > 
> > devm_kzalloc is not recommended: all devm_ memory is freed when the driver
> > is unbound, but a filehandle might still have a reference open.
> 
> How would a !devm variant with a kfree in the remove help? We would
> still fall in the same case, right?

Not quite. For video nodes this is handled: the release callback gets called
once there are no file handles open to the device. That may well be much
later than the device has been unbound from the driver.

-- 
Sakari Ailus
sakari.ailus@...ux.intel.com