linux-kernel - Re: [PATCH] soc/tegra: refactor soc_is

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Message-ID: <20181121144320.GA6446@ulmo>
Date:   Wed, 21 Nov 2018 15:43:20 +0100
From:   Thierry Reding <thierry.reding@...il.com>
To:     Jon Hunter <jonathanh@...dia.com>
Cc:     Yangtao Li <tiny.windzz@...il.com>, linux-tegra@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] soc/tegra: refactor soc_is_tegra()

On Wed, Nov 21, 2018 at 02:34:57PM +0000, Jon Hunter wrote:
> 
> On 21/11/2018 14:12, Yangtao Li wrote:
> > of_find_node_by_path() acquires a reference to the node returned by
> > it and that reference needs to be dropped by its caller.soc_is_tegra()
> > doesn't do that, so fix it.Call of_machine_is_compatible() to refactor
> > soc_is_tegra() whcih automatically manages the reference count.
> > 
> > Signed-off-by: Yangtao Li <tiny.windzz@...il.com>
> > ---
> >  drivers/soc/tegra/common.c | 12 +++++++-----
> >  1 file changed, 7 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/soc/tegra/common.c b/drivers/soc/tegra/common.c
> > index cd8f41351add..0b40700b672a 100644
> > --- a/drivers/soc/tegra/common.c
> > +++ b/drivers/soc/tegra/common.c
> > @@ -22,11 +22,13 @@ static const struct of_device_id tegra_machine_match[] = {
> >  
> >  bool soc_is_tegra(void)
> >  {
> > -	struct device_node *root;
> > +	struct of_device_id *match = tegra_machine_match;
> >  
> > -	root = of_find_node_by_path("/");
> > -	if (!root)
> > -		return false;
> > +	while(match->compatible){
> > +		if(of_machine_is_compatible(match->compatible))
> > +			return true;
> > +		match++;
> > +	}
> >  
> > -	return of_match_node(tegra_machine_match, root) != NULL;
> > +	return false;
> >  }
> 
> Ugh ... sorry, I thought that of_machine_is_compatible() looped through
> the matches. OK, let's stick with your initial fix.

Actually I prefer this one. Even if it is slightly more verbose, I think
it's much clearer what's actually going on. Also this hides all of the
OF node reference counting in a core function, so it's worth the extra
line, in my opinion.

Thierry

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