linux-kernel - Re: [PATCH 04/17] reset: core: add get_device()/put

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Date: Fri, 21 Jun 2024 12:16:17 +0200
From: Philipp Zabel <p.zabel@...gutronix.de>
To: Herve Codina <herve.codina@...tlin.com>, Thomas Gleixner
 <tglx@...utronix.de>, Rob Herring <robh@...nel.org>, Krzysztof Kozlowski
 <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski
 <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Lee Jones
 <lee@...nel.org>,  Arnd Bergmann <arnd@...db.de>, Horatiu Vultur
 <horatiu.vultur@...rochip.com>,  UNGLinuxDriver@...rochip.com, Andrew Lunn
 <andrew@...n.ch>, Heiner Kallweit <hkallweit1@...il.com>, Russell King
 <linux@...linux.org.uk>, Saravana Kannan <saravanak@...gle.com>, Bjorn
 Helgaas <bhelgaas@...gle.com>, Lars Povlsen <lars.povlsen@...rochip.com>,
 Steen Hegelund <Steen.Hegelund@...rochip.com>,  Daniel Machon
 <daniel.machon@...rochip.com>, Alexandre Belloni
 <alexandre.belloni@...tlin.com>
Cc: linux-kernel@...r.kernel.org, devicetree@...r.kernel.org, 
 netdev@...r.kernel.org, linux-pci@...r.kernel.org, 
 linux-arm-kernel@...ts.infradead.org, Allan Nielsen
 <allan.nielsen@...rochip.com>,  Luca Ceresoli <luca.ceresoli@...tlin.com>,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>, 
 Clément Léger <clement.leger@...tlin.com>
Subject: Re: [PATCH 04/17] reset: core: add get_device()/put_device on rcdev

On Di, 2024-04-30 at 10:37 +0200, Herve Codina wrote:
> From: Clément Léger <clement.leger@...tlin.com>
> 
> Since the rcdev structure is allocated by the reset controller drivers
> themselves, they need to exists as long as there is a consumer. A call to
> module_get() is already existing but that does not work when using
> device-tree overlays. In order to guarantee that the underlying reset
> controller device does not vanish while using it, add a get_device() call
> when retrieving a reset control from a reset controller device and a
> put_device() when releasing that control.
> 
> Signed-off-by: Clément Léger <clement.leger@...tlin.com>
> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
> ---
>  drivers/reset/core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/reset/core.c b/drivers/reset/core.c
> index dba74e857be6..999c3c41cf21 100644
> --- a/drivers/reset/core.c
> +++ b/drivers/reset/core.c
> @@ -812,6 +812,7 @@ __reset_control_get_internal(struct reset_controller_dev *rcdev,
>  	kref_init(&rstc->refcnt);
>  	rstc->acquired = acquired;
>  	rstc->shared = shared;
> +	get_device(rcdev->dev);
> 

Looks good to me, but can we put this right after the try_module_get()
above ...

>  	return rstc;
>  }
> @@ -826,6 +827,7 @@ static void __reset_control_release(struct kref *kref)
>  	module_put(rstc->rcdev->owner);
>  
>  	list_del(&rstc->list);
> +	put_device(rstc->rcdev->dev);

... and this right before module_put()?

regards
Philipp