linux-kernel - Re: [PATCH 2/2] thermal/drivers/mediatek/lvts

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Date: Tue, 9 Apr 2024 09:22:14 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Christophe JAILLET <christophe.jaillet@...adoo.fr>
Cc: "Rafael J. Wysocki" <rafael@...nel.org>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Zhang Rui <rui.zhang@...el.com>, Lukasz Luba <lukasz.luba@....com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org,
	linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 2/2] thermal/drivers/mediatek/lvts_thermal: Improve some
 memory allocation

On Mon, Apr 08, 2024 at 08:41:26PM +0200, Christophe JAILLET wrote:
> Le 08/04/2024 à 10:09, Dan Carpenter a écrit :
> > On Sun, Apr 07, 2024 at 10:01:49PM +0200, Christophe JAILLET wrote:
> > > diff --git a/drivers/thermal/mediatek/lvts_thermal.c b/drivers/thermal/mediatek/lvts_thermal.c
> > > index 3003dc350766..b133f731c5ba 100644
> > > --- a/drivers/thermal/mediatek/lvts_thermal.c
> > > +++ b/drivers/thermal/mediatek/lvts_thermal.c
> > > @@ -204,7 +204,7 @@ static const struct debugfs_reg32 lvts_regs[] = {
> > >   static int lvts_debugfs_init(struct device *dev, struct lvts_domain *lvts_td)
> > >   {
> > > -	struct debugfs_regset32 *regset;
> > > +	struct debugfs_regset32 *regsets;
> > >   	struct lvts_ctrl *lvts_ctrl;
> > >   	struct dentry *dentry;
> > >   	char name[64];
> > > @@ -214,8 +214,14 @@ static int lvts_debugfs_init(struct device *dev, struct lvts_domain *lvts_td)
> > >   	if (IS_ERR(lvts_td->dom_dentry))
> > >   		return 0;
> > > +	regsets = devm_kcalloc(dev, lvts_td->num_lvts_ctrl,
> > > +			       sizeof(*regsets), GFP_KERNEL);
> > > +	if (!regsets)
> > > +		return 0;
> > 
> > I understand that this preserved the behavior from the original code,
> > but the original code was wrong.  This should return -ENOMEM.
> 
> Hi Dan,
> I don't agree.
> 
> For me, this memory allocation is of the same type as all debugfs functions
> that we ignore the error code.
> 
> If it fails, it is not a reason good enough to have the probe fail. (anyway,
> if we are short on memory at this point other errors will likely occur)
> 

Huh.  It's an interesting point.  Fair enough.

> > 
> > > +
> > >   	for (i = 0; i < lvts_td->num_lvts_ctrl; i++) {
> > > +		struct debugfs_regset32 *regset = &regsets[i];
> > >   		lvts_ctrl = &lvts_td->lvts_ctrl[i];
> > 
> > The blank line should come after the declaration.
> 
> The blank line was already there, and in this file, it looks like the
> preferred style (even if not completely consistent)
> 
> Let see if there is some comment about 0 or -ENOMEM in case of memory
> allocation error, and if needed, I'll repost without the blank line.
> 

There is supposed to be a blank line after declarations though so I
think if you re-run checkpatch.pl -f on the file there is a checkpatch
warning now.

regards,
dan carpenter