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Message-Id: <1401606077-1739-2-git-send-email-eli.billauer@gmail.com>
Date: Sun, 1 Jun 2014 10:01:14 +0300
From: Eli Billauer <eli.billauer@...il.com>
To: tj@...nel.org
Cc: devel@...verdev.osuosl.org, gregkh@...uxfoundation.org,
bhelgaas@...gle.com, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org, shuah.kh@...sung.com,
iommu@...ts.linux-foundation.org, discuss@...-64.org,
Eli Billauer <eli.billauer@...il.com>
Subject: [PATCH v2 1/4] dma-mapping: Add devm_ interface for dma_map_single()
dmam_map_single() and dmam_unmap_single() are the managed counterparts
for the respective dma_* functions.
Note that dmam_map_single() returns a status value rather than the DMA handle.
The DMA handle is passed to the caller through a pointer in the arguments.
The reason for this API change is that dmam_map_single() allocates memory,
which may fail even if the DMA mapping is successful. On the other hand,
it seems like there's no platform-independent value for dma_handle that can
be used to indicate an error.
This leaves dmam_map_single() with no safe way to tell its caller that the
memory allocation has failed, except for returning a status as an int. Trying
to keep close to the non-devres API could also tempt programmers into using
dma_mapping_error() on the dmam_* functions. This would work incorrectly on
platforms, for which dma_mapping_error() ignores its argument, and always
returns success.
Thanks to Tejun Heo for suggesting this API.
Signed-off-by: Eli Billauer <eli.billauer@...il.com>
---
Documentation/driver-model/devres.txt | 2 +
drivers/base/dma-mapping.c | 86 +++++++++++++++++++++++++++++++++
include/linux/dma-mapping.h | 6 ++-
3 files changed, 93 insertions(+), 1 deletions(-)
diff --git a/Documentation/driver-model/devres.txt b/Documentation/driver-model/devres.txt
index e1a2707..13b8be0 100644
--- a/Documentation/driver-model/devres.txt
+++ b/Documentation/driver-model/devres.txt
@@ -266,6 +266,8 @@ DMA
dmam_declare_coherent_memory()
dmam_pool_create()
dmam_pool_destroy()
+ dmam_map_single()
+ dmam_unmap_single()
PCI
pcim_enable_device() : after success, all PCI ops become managed
diff --git a/drivers/base/dma-mapping.c b/drivers/base/dma-mapping.c
index 0ce39a3..f76ea0f 100644
--- a/drivers/base/dma-mapping.c
+++ b/drivers/base/dma-mapping.c
@@ -19,6 +19,7 @@ struct dma_devres {
size_t size;
void *vaddr;
dma_addr_t dma_handle;
+ enum dma_data_direction direction;
};
static void dmam_coherent_release(struct device *dev, void *res)
@@ -267,3 +268,88 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
return ret;
}
EXPORT_SYMBOL(dma_common_mmap);
+
+static int dmam_map_match(struct device *dev, void *res, void *match_data)
+{
+ struct dma_devres *this = res, *match = match_data;
+
+ if (this->dma_handle == match->dma_handle) {
+ WARN_ON(this->size != match->size ||
+ this->direction != match->direction);
+ return 1;
+ }
+ return 0;
+}
+
+static void dmam_map_single_release(struct device *dev, void *res)
+{
+ struct dma_devres *this = res;
+
+ dma_unmap_single(dev, this->dma_handle, this->size, this->direction);
+}
+
+/**
+ * dmam_map_single - Managed dma_map_single()
+ * @dev: Device to map DMA region for
+ * @ptr: Pointer to region
+ * @size: Size to map
+ * @direction: The mapping's direction
+ * @ret_dma_handle: Pointer to return the value of the DMA handle
+ *
+ * Managed dma_map_single(). The region mapped using this
+ * function will be automatically unmapped on driver detach.
+ *
+ * RETURNED VALUE:
+ * 0 is returned on success
+ * -EIO if the DMA mapping failed
+ * -ENOMEM on failure to allocate memory for internal data structure
+ */
+int dmam_map_single(struct device *dev, void *ptr, size_t size,
+ enum dma_data_direction direction,
+ dma_addr_t *ret_dma_handle)
+
+{
+ struct dma_devres *dr;
+ dma_addr_t dma_handle;
+
+ dr = devres_alloc(dmam_map_single_release, sizeof(*dr), GFP_KERNEL);
+ if (!dr)
+ return -ENOMEM;
+
+ dma_handle = dma_map_single(dev, ptr, size, direction);
+ if (dma_mapping_error(dev, dma_handle)) {
+ devres_free(dr);
+ return -EIO;
+ }
+
+ *ret_dma_handle = dma_handle;
+
+ dr->vaddr = ptr;
+ dr->dma_handle = dma_handle;
+ dr->size = size;
+ dr->direction = direction;
+
+ devres_add(dev, dr);
+
+ return 0; /* Success */
+}
+EXPORT_SYMBOL(dmam_map_single);
+
+/**
+ * dmam_unmap_single - Managed dma_unmap_single()
+ * @dev: Device to map DMA region for
+ * @dma_handle: DMA handle of the region to unmap
+ * @size: Size to unmap
+ * @direction: The mapping's direction
+ *
+ * Managed dma_unmap_single().
+ */
+void dmam_unmap_single(struct device *dev, dma_addr_t dma_handle,
+ size_t size, enum dma_data_direction direction)
+{
+ struct dma_devres match_data = { size, NULL, dma_handle, direction };
+
+ WARN_ON(devres_release(dev, dmam_map_single_release, dmam_map_match,
+ &match_data));
+}
+EXPORT_SYMBOL(dmam_unmap_single);
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h
index fd4aee2..cad63de 100644
--- a/include/linux/dma-mapping.h
+++ b/include/linux/dma-mapping.h
@@ -233,7 +233,11 @@ static inline void dmam_release_declared_memory(struct device *dev)
{
}
#endif /* ARCH_HAS_DMA_DECLARE_COHERENT_MEMORY */
-
+int dmam_map_single(struct device *dev, void *ptr, size_t size,
+ enum dma_data_direction direction,
+ dma_addr_t *ret_dma_handle);
+void dmam_unmap_single(struct device *dev, dma_addr_t dma_handle,
+ size_t size, enum dma_data_direction direction);
#ifndef CONFIG_HAVE_DMA_ATTRS
struct dma_attrs;
--
1.7.2.3
--
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