linux-kernel - Re: [PATCH 4.19 27/38] iommu/exynos: add missing put_device() call in exynos_iommu_of

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Date:   Tue, 13 Oct 2020 16:14:21 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Marek Szyprowski <m.szyprowski@...sung.com>
Cc:     Pavel Machek <pavel@...x.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Yu Kuai <yukuai3@...wei.com>, Joerg Roedel <jroedel@...e.de>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 4.19 27/38] iommu/exynos: add missing put_device() call
 in exynos_iommu_of_xlate()

Hi!
> >> From: Yu Kuai <yukuai3@...wei.com>
> >>
> >> [ Upstream commit 1a26044954a6d1f4d375d5e62392446af663be7a ]
> >>
> >> if of_find_device_by_node() succeed, exynos_iommu_of_xlate() doesn't have
> >> a corresponding put_device(). Thus add put_device() to fix the exception
> >> handling for this function implementation.
> > Okay, this looks reasonable, but...
> >
> > Do we miss put_device() in normal path, too? I'd expect another
> > put_device at end of exynos_iommu_of_xlate() or perhaps in release
> > path somewhere...
> 
> Frankly, there is no release path, so there is no need for put_device. 
> Once initialized, Exynos IOMMU stays in the system forever. There is no 
> point to remove IOMMU nor the API for that. Keeping increased refcount 
> for its device just matches this behavior.
> 
> If the missing put_device() is really a problem, then we can move it 
> from the error path just after data = platform_get_drvdata(sysmmu) 
> assignment. Feel free to send a patch if you think this is a more 
> appropriate approach.

exynos_iommu_detach_device() looks like a place where resources could
be freed? But if there's no release path, we don't really need to do anything. 

Sorry about the noise.

Best regards,
								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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