linux-kernel - Re: [PATCH] PCI: j721e: In j721e_pcie_suspend_noirq() check reset

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Message-ID: <6c7cb07c-af9e-4f69-84df-2b59a57e4182@bootlin.com>
Date: Wed, 11 Dec 2024 09:59:30 +0100
From: Thomas Richard <thomas.richard@...tlin.com>
To: Bjorn Helgaas <helgaas@...nel.org>
Cc: vigneshr@...com, s-vadapalli@...com, lpieralisi@...nel.org, kw@...ux.com,
 manivannan.sadhasivam@...aro.org, robh@...nel.org, bhelgaas@...gle.com,
 theo.lebrun@...tlin.com, thomas.petazzoni@...tlin.com,
 kwilczynski@...nel.org, linux-omap@...r.kernel.org,
 linux-pci@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, gregory.clement@...tlin.com, u-kumar1@...com
Subject: Re: [PATCH] PCI: j721e: In j721e_pcie_suspend_noirq() check
 reset_gpio before to use it

On 12/10/24 16:42, Bjorn Helgaas wrote:
> On Mon, Dec 09, 2024 at 12:23:21PM +0100, Thomas Richard wrote:
>> The reset_gpio is optional, so in j721e_pcie_suspend_noirq() check if it is
>> not NULL before to use it.
> 
> If you have occasion to post a v2, update subject to:
> 
>   PCI: j721e: Check reset_gpio for NULL before using it
> 
> s/before to use it/before using it/
> 
> Did you trip over a NULL pointer dereference here?  Or maybe found via
> inspection?

By inspection

> 
> It looks like gpiod_set_value_cansleep(desc) *should* be a no-op if
> desc is NULL, based on this comment [1]:
> 
>  * This descriptor validation needs to be inserted verbatim into each
>  * function taking a descriptor, so we need to use a preprocessor
>  * macro to avoid endless duplication. If the desc is NULL it is an
>  * optional GPIO and calls should just bail out.
> 
> and the fact that the VALIDATE_DESC_VOID() macro looks like it would
> return early in that case.
> 
> [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/gpio/gpiolib.c?id=v6.12#n2316

Oh yes you're right.
In fact, the if statement in probe() and resume_noirq() is for msleep(),
not really for gpiod_set_value_cansleep().

So this patch is useless.

Regards,

Thomas