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Subject[PATCH] 2.4 add __dma_buffer alignment macro
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Date
Following up on the "PCI DMA to small buffers on cache-incoherent
arch" discussion, here is a patch that adds <asm/dma_buffer.h>, which
contains a __dma_buffer alignment macro for DMA into buffers in the
middle of structures.

I only implemented for i386 and ppc, I don't know enough about other
architectures to get them right.

Thanks,
Roland

Documentation/DMA-mapping.txt | 27 +++++++++++++++++++++++++++
include/asm-alpha/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-arm/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-cris/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-i386/dma_buffer.h | 23 +++++++++++++++++++++++
include/asm-ia64/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-m68k/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-mips/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-mips64/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-parisc/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-ppc/dma_buffer.h | 38 ++++++++++++++++++++++++++++++++++++++
include/asm-s390/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-s390x/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-sh/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-sparc/dma_buffer.h | 22 ++++++++++++++++++++++
include/asm-sparc64/dma_buffer.h | 22 ++++++++++++++++++++++
16 files changed, 374 insertions(+)
diff -Naur linux-2.4.18.orig/Documentation/DMA-mapping.txt linux-2.4.18/Documentation/DMA-mapping.txt
--- linux-2.4.18.orig/Documentation/DMA-mapping.txt Mon Feb 25 11:37:51 2002
+++ linux-2.4.18/Documentation/DMA-mapping.txt Wed Jun 12 13:38:30 2002
@@ -67,6 +67,33 @@
networking subsystems make sure that the buffers they use are valid
for you to DMA from/to.

+Note that on non-cache-coherent architectures, having a DMA buffer
+that shares a cache line with other data can lead to memory
+corruption. The __dma_buffer macro defined in <asm/dma_buffer.h>
+exists to allow safe DMA buffers to be declared easily and portably as
+part of larger structures without causing bloat on cache-coherent
+architectures. Of course these structures must be contained in memory
+that can be used for DMA as described above.
+
+To use __dma_buffer, just declare a struct like:
+
+ struct mydevice {
+ int field1;
+ char buffer[BUFFER_SIZE] __dma_buffer;
+ int field2;
+ };
+
+If this is used in code like:
+
+ struct mydevice *dev;
+ dev = kmalloc(sizeof *dev, GFP_KERNEL);
+
+then dev->buffer will be safe for DMA on all architectures. On a
+cache-coherent architecture the members of dev will be aligned exactly
+as they would have been without __dma_buffer; on a non-cache-coherent
+architecture buffer and field2 will be aligned so that buffer does not
+share a cache line with any other data.
+
DMA addressing limitations

Does your device have any DMA addressing limitations? For example, is
diff -Naur linux-2.4.18.orig/include/asm-alpha/dma_buffer.h linux-2.4.18/include/asm-alpha/dma_buffer.h
--- linux-2.4.18.orig/include/asm-alpha/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-alpha/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_ALPHA_DMA_BUFFER_H
+#define _ASM_ALPHA_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for alpha
+
+#endif /* _ASM_ALPHA_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-arm/dma_buffer.h linux-2.4.18/include/asm-arm/dma_buffer.h
--- linux-2.4.18.orig/include/asm-arm/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-arm/dma_buffer.h Wed Jun 12 13:45:45 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_ARM_DMA_BUFFER_H
+#define _ASM_ARM_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for arm
+
+#endif /* _ASM_ARM_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-cris/dma_buffer.h linux-2.4.18/include/asm-cris/dma_buffer.h
--- linux-2.4.18.orig/include/asm-cris/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-cris/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_CRIS_DMA_BUFFER_H
+#define _ASM_CRIS_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for cris
+
+#endif /* _ASM_CRIS_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-i386/dma_buffer.h linux-2.4.18/include/asm-i386/dma_buffer.h
--- linux-2.4.18.orig/include/asm-i386/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-i386/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,23 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_I386_DMA_BUFFER_H
+#define _ASM_I386_DMA_BUFFER_H
+
+/* We have cache-coherent DMA so __dma_buffer is defined to be a NOP */
+#define __dma_buffer
+
+#endif /* _ASM_I386_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-ia64/dma_buffer.h linux-2.4.18/include/asm-ia64/dma_buffer.h
--- linux-2.4.18.orig/include/asm-ia64/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-ia64/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_IA64_DMA_BUFFER_H
+#define _ASM_IA64_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for ia64
+
+#endif /* _ASM_IA64_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-m68k/dma_buffer.h linux-2.4.18/include/asm-m68k/dma_buffer.h
--- linux-2.4.18.orig/include/asm-m68k/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-m68k/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_M68K_DMA_BUFFER_H
+#define _ASM_M68K_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for m68k
+
+#endif /* _ASM_M68K_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-mips/dma_buffer.h linux-2.4.18/include/asm-mips/dma_buffer.h
--- linux-2.4.18.orig/include/asm-mips/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-mips/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_MIPS_DMA_BUFFER_H
+#define _ASM_MIPS_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for mips
+
+#endif /* _ASM_MIPS_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-mips64/dma_buffer.h linux-2.4.18/include/asm-mips64/dma_buffer.h
--- linux-2.4.18.orig/include/asm-mips64/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-mips64/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_MIPS64_DMA_BUFFER_H
+#define _ASM_MIPS64_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for mips64
+
+#endif /* _ASM_MIPS64_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-parisc/dma_buffer.h linux-2.4.18/include/asm-parisc/dma_buffer.h
--- linux-2.4.18.orig/include/asm-parisc/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-parisc/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_PARISC_DMA_BUFFER_H
+#define _ASM_PARISC_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for parisc
+
+#endif /* _ASM_PARISC_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-ppc/dma_buffer.h linux-2.4.18/include/asm-ppc/dma_buffer.h
--- linux-2.4.18.orig/include/asm-ppc/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-ppc/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,38 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version. */
+
+#ifdef __KERNEL__
+#ifndef _ASM_PPC_DMA_BUFFER_H
+#define _ASM_PPC_DMA_BUFFER_H
+
+#include <linux/config.h>
+
+#ifdef CONFIG_NOT_COHERENT_CACHE
+
+#include <asm/cache.h>
+
+#define __dma_buffer __dma_buffer_line(__LINE__)
+#define __dma_buffer_line(line) __dma_buffer_expand_line(line)
+#define __dma_buffer_expand_line(line) \
+ __attribute__ ((aligned(L1_CACHE_BYTES))); \
+ char __dma_pad_ ## line [0] __attribute__ ((aligned(L1_CACHE_BYTES)))
+
+#else /* CONFIG_NOT_COHERENT_CACHE */
+
+/* We have cache-coherent DMA so __dma_buffer is defined to be a NOP */
+#define __dma_buffer
+
+#endif /* CONFIG_NOT_COHERENT_CACHE */
+
+#endif /* _ASM_PPC_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-s390/dma_buffer.h linux-2.4.18/include/asm-s390/dma_buffer.h
--- linux-2.4.18.orig/include/asm-s390/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-s390/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_S390_DMA_BUFFER_H
+#define _ASM_S390_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for s390
+
+#endif /* _ASM_S390_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-s390x/dma_buffer.h linux-2.4.18/include/asm-s390x/dma_buffer.h
--- linux-2.4.18.orig/include/asm-s390x/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-s390x/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_S390X_DMA_BUFFER_H
+#define _ASM_S390X_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for s390x
+
+#endif /* _ASM_S390X_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-sh/dma_buffer.h linux-2.4.18/include/asm-sh/dma_buffer.h
--- linux-2.4.18.orig/include/asm-sh/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-sh/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_SH_DMA_BUFFER_H
+#define _ASM_SH_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for sh
+
+#endif /* _ASM_SH_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-sparc/dma_buffer.h linux-2.4.18/include/asm-sparc/dma_buffer.h
--- linux-2.4.18.orig/include/asm-sparc/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-sparc/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_SPARC_DMA_BUFFER_H
+#define _ASM_SPARC_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for sparc
+
+#endif /* _ASM_SPARC_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
diff -Naur linux-2.4.18.orig/include/asm-sparc64/dma_buffer.h linux-2.4.18/include/asm-sparc64/dma_buffer.h
--- linux-2.4.18.orig/include/asm-sparc64/dma_buffer.h Wed Dec 31 16:00:00 1969
+++ linux-2.4.18/include/asm-sparc64/dma_buffer.h Wed Jun 12 13:38:30 2002
@@ -0,0 +1,22 @@
+/*
+ * __dma_buffer macro for safe DMA into struct members
+ *
+ * See "What memory is DMA'able?" in Documentation/DMA-mapping.txt
+ * for more information.
+ *
+ * Copyright (c) 2002 Roland Dreier <roland@digitalvampire.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+#ifdef __KERNEL__
+#ifndef _ASM_SPARC64_DMA_BUFFER_H
+#define _ASM_SPARC64_DMA_BUFFER_H
+
+#warning <asm/dma_buffer.h> is not implemented yet for sparc64
+
+#endif /* _ASM_SPARC64_DMA_BUFFER_H */
+#endif /* __KERNEL__ */
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