linux-kernel - [RFC PATCH 5/5] iommu/dma: Add iommu_dma

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Message-Id: <20170705071215.17603-6-tfiga@chromium.org>
Date:   Wed,  5 Jul 2017 16:12:15 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     iommu@...ts.linux-foundation.org
Cc:     linux-kernel@...r.kernel.org, Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joerg Roedel <joro@...tes.org>,
        Will Deacon <will.deacon@....com>,
        Vineet Gupta <vgupta@...opsys.com>,
        Hans-Christian Noren Egtvedt <egtvedt@...fundet.no>,
        Mitchel Humpherys <mitchelh@...eaurora.org>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Tomasz Figa <tfiga@...omium.org>
Subject: [RFC PATCH 5/5] iommu/dma: Add iommu_dma_cleanup()

In case of loadable modules using dma-iommu helpers, it makes sense to
drop the reference to the iova cache on module exit. Add a helper called
iommu_dma_cleanup() that undoes the effects of iommu_dma_init(), so that
modules can be unloaded cleanly.

Signed-off-by: Tomasz Figa <tfiga@...omium.org>
---
 drivers/iommu/dma-iommu.c | 6 ++++++
 include/linux/dma-iommu.h | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 7cdeaf930106..51afa18a5de1 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -82,6 +82,12 @@ int iommu_dma_init(void)
 }
 EXPORT_SYMBOL(iommu_dma_init);
 
+void iommu_dma_cleanup(void)
+{
+	iova_cache_put();
+}
+EXPORT_SYMBOL(iommu_dma_cleanup);
+
 /**
  * iommu_get_dma_cookie - Acquire DMA-API resources for a domain
  * @domain: IOMMU domain to prepare for DMA-API usage
diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
index 92f20832fd28..b12d9207a87a 100644
--- a/include/linux/dma-iommu.h
+++ b/include/linux/dma-iommu.h
@@ -24,7 +24,9 @@
 #include <linux/iommu.h>
 #include <linux/msi.h>
 
+/* Framework initialization - reference counted */
 int iommu_dma_init(void);
+void iommu_dma_cleanup(void);
 
 /* Domain management interface for IOMMU drivers */
 int iommu_get_dma_cookie(struct iommu_domain *domain);
@@ -85,6 +87,10 @@ static inline int iommu_dma_init(void)
 	return 0;
 }
 
+static inline void iommu_dma_cleanup(void)
+{
+}
+
 static inline int iommu_get_dma_cookie(struct iommu_domain *domain)
 {
 	return -ENODEV;
-- 
2.13.2.725.g09c95d1e9-goog