linux-kernel - RE: [PATCH] crypto: tegra - Remove an incorrect iommu_fwspec_free() call in tegra_se

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Date: Fri, 31 May 2024 05:36:48 +0000
From: Akhil R <akhilrajeev@...dia.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
CC: Christophe JAILLET <christophe.jaillet@...adoo.fr>, "David S. Miller"
	<davem@...emloft.net>, Thierry Reding <thierry.reding@...il.com>, Jon Hunter
	<jonathanh@...dia.com>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "kernel-janitors@...r.kernel.org"
	<kernel-janitors@...r.kernel.org>, "linux-crypto@...r.kernel.org"
	<linux-crypto@...r.kernel.org>, "linux-tegra@...r.kernel.org"
	<linux-tegra@...r.kernel.org>
Subject: RE: [PATCH] crypto: tegra - Remove an incorrect iommu_fwspec_free()
 call in tegra_se_remove()



> -----Original Message-----
> From: Herbert Xu <herbert@...dor.apana.org.au>
> Sent: Friday, May 31, 2024 10:53 AM
> To: Akhil R <akhilrajeev@...dia.com>
> Cc: Christophe JAILLET <christophe.jaillet@...adoo.fr>; David S. Miller
> <davem@...emloft.net>; Thierry Reding <thierry.reding@...il.com>; Jon
> Hunter <jonathanh@...dia.com>; linux-kernel@...r.kernel.org; kernel-
> janitors@...r.kernel.org; linux-crypto@...r.kernel.org; linux-
> tegra@...r.kernel.org
> Subject: Re: [PATCH] crypto: tegra - Remove an incorrect iommu_fwspec_free()
> call in tegra_se_remove()
> 
> External email: Use caution opening links or attachments
> 
> 
> On Wed, May 29, 2024 at 06:53:42AM +0000, Akhil R wrote:
> > > The only iommu function call in this driver is a
> > > tegra_dev_iommu_get_stream_id() which does not allocate anything and
> does
> > > not take any reference.
> > >
> > > More-over, what is freed is "se->dev" which has been devm_kzalloc()'ed in the
> > > probe.
> >
> > I did not completely understand what is being tried to convey here.
> > If I understand it right, iommu_fwspec_free() does not do anything
> > with the "devm_kzalloc"ed variable.
> >
> > It would probably be a good idea to remove this line from the commit message.
> 
> I think he means that as the memory was allocated via devm, it will
> be automatically freed by the kernel and the driver does not need
> to (and should not) free the memory by hand.

Ya. But iommu_fwspec_free() does not free the memory allocated via devm.

I think iommu_fwspec_free() is expected to be called in symmetry with
iommu_fwspec_init(). So, I do agree that the SE driver does not allocate
what is freed by iommu_fwspec_free(), but I feel this line is a bit misleading.