linux-kernel - Re: [PATCH v3 1/7] mfd: syscon: Add reference counting and device managed support

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Message-ID: <20240711182528.1402892d@bootlin.com>
Date: Thu, 11 Jul 2024 18:25:28 +0200
From: Herve Codina <herve.codina@...tlin.com>
To: Markus Elfring <Markus.Elfring@....de>, Lee Jones <lee@...nel.org>
Cc: Clément Léger <clement.leger@...tlin.com>,
 devicetree@...r.kernel.org, linux-pci@...r.kernel.org,
 netdev@...r.kernel.org, UNGLinuxDriver@...rochip.com,
 linux-arm-kernel@...ts.infradead.org, Andy Shevchenko
 <andy.shevchenko@...il.com>, Arnd Bergmann <arnd@...db.de>, Bjorn Helgaas
 <bhelgaas@...gle.com>, Conor Dooley <conor+dt@...nel.org>, Daniel Machon
 <daniel.machon@...rochip.com>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
 Lars Povlsen <lars.povlsen@...rochip.com>, Philipp Zabel
 <p.zabel@...gutronix.de>, Rob Herring <robh@...nel.org>, Saravana Kannan
 <saravanak@...gle.com>, Simon Horman <horms@...nel.org>, Steen Hegelund
 <Steen.Hegelund@...rochip.com>, LKML <linux-kernel@...r.kernel.org>, Allan
 Nielsen <allan.nielsen@...rochip.com>, Andrew Lunn <andrew@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Horatiu Vultur <horatiu.vultur@...rochip.com>, Jakub Kicinski
 <kuba@...nel.org>, Luca Ceresoli <luca.ceresoli@...tlin.com>, Paolo Abeni
 <pabeni@...hat.com>, Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v3 1/7] mfd: syscon: Add reference counting and device
 managed support

Hi Markus,

On Thu, 11 Jul 2024 18:09:26 +0200
Markus Elfring <Markus.Elfring@....de> wrote:

> …
> > +++ b/drivers/mfd/syscon.c  
> …
> > +static struct syscon *syscon_from_regmap(struct regmap *regmap)  
> +{
> > +	struct syscon *entry, *syscon = NULL;
> > +
> > +	spin_lock(&syscon_list_slock);
> > +
> > +	list_for_each_entry(entry, &syscon_list, list)  
> …
> > +	spin_unlock(&syscon_list_slock);
> > +
> > +	return syscon;
> > +}  
> …
> 
> Under which circumstances would you become interested to apply a statement
> like “guard(spinlock)(&syscon_list_slock);”?
> https://elixir.bootlin.com/linux/v6.10-rc7/source/include/linux/spinlock.h#L561
> 

I used the spin_{lock,unlock}() pattern call already present in syscon.c.
Of course, I can add a new patch in this series converting syscon.c to
the guard() family and use guard() in my introduced lock/unlock.

Lee, any opinion ?

Best regards,
Hervé