dma-buf-map: Rename to iosys-map

Rename struct dma_buf_map to struct iosys_map and corresponding APIs.
Over time dma-buf-map grew up to more functionality than the one used by
dma-buf: in fact it's just a shim layer to abstract system memory, that
can be accessed via regular load and store, from IO memory that needs to
be acessed via arch helpers.

The idea is to extend this API so it can fulfill other needs, internal
to a single driver. Example: in the i915 driver it's desired to share
the implementation for integrated graphics, which uses mostly system
memory, with discrete graphics, which may need to access IO memory.

The conversion was mostly done with the following semantic patch:

	@r1@
	@@
	- struct dma_buf_map
	+ struct iosys_map

	@r2@
	@@
	(
	- DMA_BUF_MAP_INIT_VADDR
	+ IOSYS_MAP_INIT_VADDR
	|
	- dma_buf_map_set_vaddr
	+ iosys_map_set_vaddr
	|
	- dma_buf_map_set_vaddr_iomem
	+ iosys_map_set_vaddr_iomem
	|
	- dma_buf_map_is_equal
	+ iosys_map_is_equal
	|
	- dma_buf_map_is_null
	+ iosys_map_is_null
	|
	- dma_buf_map_is_set
	+ iosys_map_is_set
	|
	- dma_buf_map_clear
	+ iosys_map_clear
	|
	- dma_buf_map_memcpy_to
	+ iosys_map_memcpy_to
	|
	- dma_buf_map_incr
	+ iosys_map_incr
	)

	@@
	@@
	- #include <linux/dma-buf-map.h>
	+ #include <linux/iosys-map.h>

Then some files had their includes adjusted and some comments were
update to remove mentions to dma-buf-map.

Since this is not specific to dma-buf anymore, move the documentation to
the "Bus-Independent Device Accesses" section.

v2:
  - Squash patches

v3:
  - Fix wrong removal of dma-buf.h from MAINTAINERS
  - Move documentation from dma-buf.rst to device-io.rst

v4:
  - Change documentation title and level

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Acked-by: Christian König <christian.koenig@amd.com>
Acked-by: Sumit Semwal <sumit.semwal@linaro.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220204170541.829227-1-lucas.demarchi@intel.com

3 files changed, 263 insertions, 272 deletions

diff --git a/include/linux/dma-buf-map.h b/include/linux/dma-buf-map.h
deleted file mode 100644
index 278d489e4bdd..000000000000
--- a/include/linux/dma-buf-map.h
+++ /dev/null
@@ -1,266 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0-only */
-/*
- * Pointer to dma-buf-mapped memory, plus helpers.
- */
-
-#ifndef __DMA_BUF_MAP_H__
-#define __DMA_BUF_MAP_H__
-
-#include <linux/io.h>
-#include <linux/string.h>
-
-/**
- * DOC: overview
- *
- * Calling dma-buf's vmap operation returns a pointer to the buffer's memory.
- * Depending on the location of the buffer, users may have to access it with
- * I/O operations or memory load/store operations. For example, copying to
- * system memory could be done with memcpy(), copying to I/O memory would be
- * done with memcpy_toio().
- *
- * .. code-block:: c
- *
- *	void *vaddr = ...; // pointer to system memory
- *	memcpy(vaddr, src, len);
- *
- *	void *vaddr_iomem = ...; // pointer to I/O memory
- *	memcpy_toio(vaddr, _iomem, src, len);
- *
- * When using dma-buf's vmap operation, the returned pointer is encoded as
- * :c:type:`struct dma_buf_map <dma_buf_map>`.
- * :c:type:`struct dma_buf_map <dma_buf_map>` stores the buffer's address in
- * system or I/O memory and a flag that signals the required method of
- * accessing the buffer. Use the returned instance and the helper functions
- * to access the buffer's memory in the correct way.
- *
- * The type :c:type:`struct dma_buf_map <dma_buf_map>` and its helpers are
- * actually independent from the dma-buf infrastructure. When sharing buffers
- * among devices, drivers have to know the location of the memory to access
- * the buffers in a safe way. :c:type:`struct dma_buf_map <dma_buf_map>`
- * solves this problem for dma-buf and its users. If other drivers or
- * sub-systems require similar functionality, the type could be generalized
- * and moved to a more prominent header file.
- *
- * Open-coding access to :c:type:`struct dma_buf_map <dma_buf_map>` is
- * considered bad style. Rather then accessing its fields directly, use one
- * of the provided helper functions, or implement your own. For example,
- * instances of :c:type:`struct dma_buf_map <dma_buf_map>` can be initialized
- * statically with DMA_BUF_MAP_INIT_VADDR(), or at runtime with
- * dma_buf_map_set_vaddr(). These helpers will set an address in system memory.
- *
- * .. code-block:: c
- *
- *	struct dma_buf_map map = DMA_BUF_MAP_INIT_VADDR(0xdeadbeaf);
- *
- *	dma_buf_map_set_vaddr(&map. 0xdeadbeaf);
- *
- * To set an address in I/O memory, use dma_buf_map_set_vaddr_iomem().
- *
- * .. code-block:: c
- *
- *	dma_buf_map_set_vaddr_iomem(&map. 0xdeadbeaf);
- *
- * Instances of struct dma_buf_map do not have to be cleaned up, but
- * can be cleared to NULL with dma_buf_map_clear(). Cleared mappings
- * always refer to system memory.
- *
- * .. code-block:: c
- *
- *	dma_buf_map_clear(&map);
- *
- * Test if a mapping is valid with either dma_buf_map_is_set() or
- * dma_buf_map_is_null().
- *
- * .. code-block:: c
- *
- *	if (dma_buf_map_is_set(&map) != dma_buf_map_is_null(&map))
- *		// always true
- *
- * Instances of :c:type:`struct dma_buf_map <dma_buf_map>` can be compared
- * for equality with dma_buf_map_is_equal(). Mappings the point to different
- * memory spaces, system or I/O, are never equal. That's even true if both
- * spaces are located in the same address space, both mappings contain the
- * same address value, or both mappings refer to NULL.
- *
- * .. code-block:: c
- *
- *	struct dma_buf_map sys_map; // refers to system memory
- *	struct dma_buf_map io_map; // refers to I/O memory
- *
- *	if (dma_buf_map_is_equal(&sys_map, &io_map))
- *		// always false
- *
- * A set up instance of struct dma_buf_map can be used to access or manipulate
- * the buffer memory. Depending on the location of the memory, the provided
- * helpers will pick the correct operations. Data can be copied into the memory
- * with dma_buf_map_memcpy_to(). The address can be manipulated with
- * dma_buf_map_incr().
- *
- * .. code-block:: c
- *
- *	const void *src = ...; // source buffer
- *	size_t len = ...; // length of src
- *
- *	dma_buf_map_memcpy_to(&map, src, len);
- *	dma_buf_map_incr(&map, len); // go to first byte after the memcpy
- */
-
-/**
- * struct dma_buf_map - Pointer to vmap'ed dma-buf memory.
- * @vaddr_iomem:	The buffer's address if in I/O memory
- * @vaddr:		The buffer's address if in system memory
- * @is_iomem:		True if the dma-buf memory is located in I/O
- *			memory, or false otherwise.
- */
-struct dma_buf_map {
-	union {
-		void __iomem *vaddr_iomem;
-		void *vaddr;
-	};
-	bool is_iomem;
-};
-
-/**
- * DMA_BUF_MAP_INIT_VADDR - Initializes struct dma_buf_map to an address in system memory
- * @vaddr_:	A system-memory address
- */
-#define DMA_BUF_MAP_INIT_VADDR(vaddr_) \
-	{ \
-		.vaddr = (vaddr_), \
-		.is_iomem = false, \
-	}
-
-/**
- * dma_buf_map_set_vaddr - Sets a dma-buf mapping structure to an address in system memory
- * @map:	The dma-buf mapping structure
- * @vaddr:	A system-memory address
- *
- * Sets the address and clears the I/O-memory flag.
- */
-static inline void dma_buf_map_set_vaddr(struct dma_buf_map *map, void *vaddr)
-{
-	map->vaddr = vaddr;
-	map->is_iomem = false;
-}
-
-/**
- * dma_buf_map_set_vaddr_iomem - Sets a dma-buf mapping structure to an address in I/O memory
- * @map:		The dma-buf mapping structure
- * @vaddr_iomem:	An I/O-memory address
- *
- * Sets the address and the I/O-memory flag.
- */
-static inline void dma_buf_map_set_vaddr_iomem(struct dma_buf_map *map,
-					       void __iomem *vaddr_iomem)
-{
-	map->vaddr_iomem = vaddr_iomem;
-	map->is_iomem = true;
-}
-
-/**
- * dma_buf_map_is_equal - Compares two dma-buf mapping structures for equality
- * @lhs:	The dma-buf mapping structure
- * @rhs:	A dma-buf mapping structure to compare with
- *
- * Two dma-buf mapping structures are equal if they both refer to the same type of memory
- * and to the same address within that memory.
- *
- * Returns:
- * True is both structures are equal, or false otherwise.
- */
-static inline bool dma_buf_map_is_equal(const struct dma_buf_map *lhs,
-					const struct dma_buf_map *rhs)
-{
-	if (lhs->is_iomem != rhs->is_iomem)
-		return false;
-	else if (lhs->is_iomem)
-		return lhs->vaddr_iomem == rhs->vaddr_iomem;
-	else
-		return lhs->vaddr == rhs->vaddr;
-}
-
-/**
- * dma_buf_map_is_null - Tests for a dma-buf mapping to be NULL
- * @map:	The dma-buf mapping structure
- *
- * Depending on the state of struct dma_buf_map.is_iomem, tests if the
- * mapping is NULL.
- *
- * Returns:
- * True if the mapping is NULL, or false otherwise.
- */
-static inline bool dma_buf_map_is_null(const struct dma_buf_map *map)
-{
-	if (map->is_iomem)
-		return !map->vaddr_iomem;
-	return !map->vaddr;
-}
-
-/**
- * dma_buf_map_is_set - Tests is the dma-buf mapping has been set
- * @map:	The dma-buf mapping structure
- *
- * Depending on the state of struct dma_buf_map.is_iomem, tests if the
- * mapping has been set.
- *
- * Returns:
- * True if the mapping is been set, or false otherwise.
- */
-static inline bool dma_buf_map_is_set(const struct dma_buf_map *map)
-{
-	return !dma_buf_map_is_null(map);
-}
-
-/**
- * dma_buf_map_clear - Clears a dma-buf mapping structure
- * @map:	The dma-buf mapping structure
- *
- * Clears all fields to zero; including struct dma_buf_map.is_iomem. So
- * mapping structures that were set to point to I/O memory are reset for
- * system memory. Pointers are cleared to NULL. This is the default.
- */
-static inline void dma_buf_map_clear(struct dma_buf_map *map)
-{
-	if (map->is_iomem) {
-		map->vaddr_iomem = NULL;
-		map->is_iomem = false;
-	} else {
-		map->vaddr = NULL;
-	}
-}
-
-/**
- * dma_buf_map_memcpy_to - Memcpy into dma-buf mapping
- * @dst:	The dma-buf mapping structure
- * @src:	The source buffer
- * @len:	The number of byte in src
- *
- * Copies data into a dma-buf mapping. The source buffer is in system
- * memory. Depending on the buffer's location, the helper picks the correct
- * method of accessing the memory.
- */
-static inline void dma_buf_map_memcpy_to(struct dma_buf_map *dst, const void *src, size_t len)
-{
-	if (dst->is_iomem)
-		memcpy_toio(dst->vaddr_iomem, src, len);
-	else
-		memcpy(dst->vaddr, src, len);
-}
-
-/**
- * dma_buf_map_incr - Increments the address stored in a dma-buf mapping
- * @map:	The dma-buf mapping structure
- * @incr:	The number of bytes to increment
- *
- * Increments the address stored in a dma-buf mapping. Depending on the
- * buffer's location, the correct value will be updated.
- */
-static inline void dma_buf_map_incr(struct dma_buf_map *map, size_t incr)
-{
-	if (map->is_iomem)
-		map->vaddr_iomem += incr;
-	else
-		map->vaddr += incr;
-}
-
-#endif /* __DMA_BUF_MAP_H__ */
diff --git a/include/linux/dma-buf.h b/include/linux/dma-buf.h
index 7ab50076e7a6..2097760e8e95 100644
--- a/include/linux/dma-buf.h
+++ b/include/linux/dma-buf.h
@@ -13,7 +13,7 @@
 #ifndef __DMA_BUF_H__
 #define __DMA_BUF_H__
 
-#include <linux/dma-buf-map.h>
+#include <linux/iosys-map.h>
 #include <linux/file.h>
 #include <linux/err.h>
 #include <linux/scatterlist.h>
@@ -283,8 +283,8 @@ struct dma_buf_ops {
 	 */
 	int (*mmap)(struct dma_buf *, struct vm_area_struct *vma);
 
-	int (*vmap)(struct dma_buf *dmabuf, struct dma_buf_map *map);
-	void (*vunmap)(struct dma_buf *dmabuf, struct dma_buf_map *map);
+	int (*vmap)(struct dma_buf *dmabuf, struct iosys_map *map);
+	void (*vunmap)(struct dma_buf *dmabuf, struct iosys_map *map);
 };
 
 /**
@@ -347,7 +347,7 @@ struct dma_buf {
 	 * @vmap_ptr:
 	 * The current vmap ptr if @vmapping_counter > 0. Protected by @lock.
 	 */
-	struct dma_buf_map vmap_ptr;
+	struct iosys_map vmap_ptr;
 
 	/**
 	 * @exp_name:
@@ -628,6 +628,6 @@ int dma_buf_end_cpu_access(struct dma_buf *dma_buf,
 
 int dma_buf_mmap(struct dma_buf *, struct vm_area_struct *,
 		 unsigned long);
-int dma_buf_vmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
-void dma_buf_vunmap(struct dma_buf *dmabuf, struct dma_buf_map *map);
+int dma_buf_vmap(struct dma_buf *dmabuf, struct iosys_map *map);
+void dma_buf_vunmap(struct dma_buf *dmabuf, struct iosys_map *map);
 #endif /* __DMA_BUF_H__ */
diff --git a/include/linux/iosys-map.h b/include/linux/iosys-map.h
new file mode 100644
index 000000000000..f4186f91caa6
--- /dev/null
+++ b/include/linux/iosys-map.h
@@ -0,0 +1,257 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * Pointer abstraction for IO/system memory
+ */
+
+#ifndef __IOSYS_MAP_H__
+#define __IOSYS_MAP_H__
+
+#include <linux/io.h>
+#include <linux/string.h>
+
+/**
+ * DOC: overview
+ *
+ * When accessing a memory region, depending on its location, users may have to
+ * access it with I/O operations or memory load/store operations. For example,
+ * copying to system memory could be done with memcpy(), copying to I/O memory
+ * would be done with memcpy_toio().
+ *
+ * .. code-block:: c
+ *
+ *	void *vaddr = ...; // pointer to system memory
+ *	memcpy(vaddr, src, len);
+ *
+ *	void *vaddr_iomem = ...; // pointer to I/O memory
+ *	memcpy_toio(vaddr, _iomem, src, len);
+ *
+ * The user of such pointer may not have information about the mapping of that
+ * region or may want to have a single code path to handle operations on that
+ * buffer, regardless if it's located in system or IO memory. The type
+ * :c:type:`struct iosys_map <iosys_map>` and its helpers abstract that so the
+ * buffer can be passed around to other drivers or have separate duties inside
+ * the same driver for allocation, read and write operations.
+ *
+ * Open-coding access to :c:type:`struct iosys_map <iosys_map>` is considered
+ * bad style. Rather then accessing its fields directly, use one of the provided
+ * helper functions, or implement your own. For example, instances of
+ * :c:type:`struct iosys_map <iosys_map>` can be initialized statically with
+ * IOSYS_MAP_INIT_VADDR(), or at runtime with iosys_map_set_vaddr(). These
+ * helpers will set an address in system memory.
+ *
+ * .. code-block:: c
+ *
+ *	struct iosys_map map = IOSYS_MAP_INIT_VADDR(0xdeadbeaf);
+ *
+ *	iosys_map_set_vaddr(&map, 0xdeadbeaf);
+ *
+ * To set an address in I/O memory, use iosys_map_set_vaddr_iomem().
+ *
+ * .. code-block:: c
+ *
+ *	iosys_map_set_vaddr_iomem(&map, 0xdeadbeaf);
+ *
+ * Instances of struct iosys_map do not have to be cleaned up, but
+ * can be cleared to NULL with iosys_map_clear(). Cleared mappings
+ * always refer to system memory.
+ *
+ * .. code-block:: c
+ *
+ *	iosys_map_clear(&map);
+ *
+ * Test if a mapping is valid with either iosys_map_is_set() or
+ * iosys_map_is_null().
+ *
+ * .. code-block:: c
+ *
+ *	if (iosys_map_is_set(&map) != iosys_map_is_null(&map))
+ *		// always true
+ *
+ * Instances of :c:type:`struct iosys_map <iosys_map>` can be compared for
+ * equality with iosys_map_is_equal(). Mappings that point to different memory
+ * spaces, system or I/O, are never equal. That's even true if both spaces are
+ * located in the same address space, both mappings contain the same address
+ * value, or both mappings refer to NULL.
+ *
+ * .. code-block:: c
+ *
+ *	struct iosys_map sys_map; // refers to system memory
+ *	struct iosys_map io_map; // refers to I/O memory
+ *
+ *	if (iosys_map_is_equal(&sys_map, &io_map))
+ *		// always false
+ *
+ * A set up instance of struct iosys_map can be used to access or manipulate the
+ * buffer memory. Depending on the location of the memory, the provided helpers
+ * will pick the correct operations. Data can be copied into the memory with
+ * iosys_map_memcpy_to(). The address can be manipulated with iosys_map_incr().
+ *
+ * .. code-block:: c
+ *
+ *	const void *src = ...; // source buffer
+ *	size_t len = ...; // length of src
+ *
+ *	iosys_map_memcpy_to(&map, src, len);
+ *	iosys_map_incr(&map, len); // go to first byte after the memcpy
+ */
+
+/**
+ * struct iosys_map - Pointer to IO/system memory
+ * @vaddr_iomem:	The buffer's address if in I/O memory
+ * @vaddr:		The buffer's address if in system memory
+ * @is_iomem:		True if the buffer is located in I/O memory, or false
+ *			otherwise.
+ */
+struct iosys_map {
+	union {
+		void __iomem *vaddr_iomem;
+		void *vaddr;
+	};
+	bool is_iomem;
+};
+
+/**
+ * IOSYS_MAP_INIT_VADDR - Initializes struct iosys_map to an address in system memory
+ * @vaddr_:	A system-memory address
+ */
+#define IOSYS_MAP_INIT_VADDR(vaddr_)	\
+	{				\
+		.vaddr = (vaddr_),	\
+		.is_iomem = false,	\
+	}
+
+/**
+ * iosys_map_set_vaddr - Sets a iosys mapping structure to an address in system memory
+ * @map:	The iosys_map structure
+ * @vaddr:	A system-memory address
+ *
+ * Sets the address and clears the I/O-memory flag.
+ */
+static inline void iosys_map_set_vaddr(struct iosys_map *map, void *vaddr)
+{
+	map->vaddr = vaddr;
+	map->is_iomem = false;
+}
+
+/**
+ * iosys_map_set_vaddr_iomem - Sets a iosys mapping structure to an address in I/O memory
+ * @map:		The iosys_map structure
+ * @vaddr_iomem:	An I/O-memory address
+ *
+ * Sets the address and the I/O-memory flag.
+ */
+static inline void iosys_map_set_vaddr_iomem(struct iosys_map *map,
+					     void __iomem *vaddr_iomem)
+{
+	map->vaddr_iomem = vaddr_iomem;
+	map->is_iomem = true;
+}
+
+/**
+ * iosys_map_is_equal - Compares two iosys mapping structures for equality
+ * @lhs:	The iosys_map structure
+ * @rhs:	A iosys_map structure to compare with
+ *
+ * Two iosys mapping structures are equal if they both refer to the same type of memory
+ * and to the same address within that memory.
+ *
+ * Returns:
+ * True is both structures are equal, or false otherwise.
+ */
+static inline bool iosys_map_is_equal(const struct iosys_map *lhs,
+				      const struct iosys_map *rhs)
+{
+	if (lhs->is_iomem != rhs->is_iomem)
+		return false;
+	else if (lhs->is_iomem)
+		return lhs->vaddr_iomem == rhs->vaddr_iomem;
+	else
+		return lhs->vaddr == rhs->vaddr;
+}
+
+/**
+ * iosys_map_is_null - Tests for a iosys mapping to be NULL
+ * @map:	The iosys_map structure
+ *
+ * Depending on the state of struct iosys_map.is_iomem, tests if the
+ * mapping is NULL.
+ *
+ * Returns:
+ * True if the mapping is NULL, or false otherwise.
+ */
+static inline bool iosys_map_is_null(const struct iosys_map *map)
+{
+	if (map->is_iomem)
+		return !map->vaddr_iomem;
+	return !map->vaddr;
+}
+
+/**
+ * iosys_map_is_set - Tests if the iosys mapping has been set
+ * @map:	The iosys_map structure
+ *
+ * Depending on the state of struct iosys_map.is_iomem, tests if the
+ * mapping has been set.
+ *
+ * Returns:
+ * True if the mapping is been set, or false otherwise.
+ */
+static inline bool iosys_map_is_set(const struct iosys_map *map)
+{
+	return !iosys_map_is_null(map);
+}
+
+/**
+ * iosys_map_clear - Clears a iosys mapping structure
+ * @map:	The iosys_map structure
+ *
+ * Clears all fields to zero, including struct iosys_map.is_iomem, so
+ * mapping structures that were set to point to I/O memory are reset for
+ * system memory. Pointers are cleared to NULL. This is the default.
+ */
+static inline void iosys_map_clear(struct iosys_map *map)
+{
+	if (map->is_iomem) {
+		map->vaddr_iomem = NULL;
+		map->is_iomem = false;
+	} else {
+		map->vaddr = NULL;
+	}
+}
+
+/**
+ * iosys_map_memcpy_to - Memcpy into iosys mapping
+ * @dst:	The iosys_map structure
+ * @src:	The source buffer
+ * @len:	The number of byte in src
+ *
+ * Copies data into a iosys mapping. The source buffer is in system
+ * memory. Depending on the buffer's location, the helper picks the correct
+ * method of accessing the memory.
+ */
+static inline void iosys_map_memcpy_to(struct iosys_map *dst, const void *src,
+				       size_t len)
+{
+	if (dst->is_iomem)
+		memcpy_toio(dst->vaddr_iomem, src, len);
+	else
+		memcpy(dst->vaddr, src, len);
+}
+
+/**
+ * iosys_map_incr - Increments the address stored in a iosys mapping
+ * @map:	The iosys_map structure
+ * @incr:	The number of bytes to increment
+ *
+ * Increments the address stored in a iosys mapping. Depending on the
+ * buffer's location, the correct value will be updated.
+ */
+static inline void iosys_map_incr(struct iosys_map *map, size_t incr)
+{
+	if (map->is_iomem)
+		map->vaddr_iomem += incr;
+	else
+		map->vaddr += incr;
+}
+
+#endif /* __IOSYS_MAP_H__ */