linux-kernel - [PATCH 22/28] x86: use a fallback dev for i386

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Date:	Tue,  8 Apr 2008 13:21:04 -0300
From:	Glauber Costa <gcosta@...hat.com>
To:	linux-kernel@...r.kernel.org
Cc:	akpm@...ux-foundation.org, glommer@...il.com, mingo@...e.hu,
	tglx@...utronix.de, kvm-devel@...ts.sourceforge.net,
	amit.shah@...ranet.com, avi@...ranet.com,
	Glauber Costa <gcosta@...hat.com>
Subject: [PATCH 22/28] x86: use a fallback dev for i386

We can use a fallback dev for cases of a NULL device being passed (mostly ISA)
This comes from x86_64 implementation.

Signed-off-by: Glauber Costa <gcosta@...hat.com>
---
 arch/x86/kernel/pci-dma_32.c |   13 +++++++++++++
 1 files changed, 13 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/pci-dma_32.c b/arch/x86/kernel/pci-dma_32.c
index f6cf434..0e9ec11 100644
--- a/arch/x86/kernel/pci-dma_32.c
+++ b/arch/x86/kernel/pci-dma_32.c
@@ -14,6 +14,16 @@
 #include <linux/module.h>
 #include <asm/io.h>
 
+/* Dummy device used for NULL arguments (normally ISA). Better would
+   be probably a smaller DMA mask, but this is bug-to-bug compatible
+   to i386. */
+struct device fallback_dev = {
+	.bus_id = "fallback device",
+	.coherent_dma_mask = DMA_32BIT_MASK,
+	.dma_mask = &fallback_dev.coherent_dma_mask,
+};
+
+
 static int dma_alloc_from_coherent_mem(struct device *dev, ssize_t size,
 				       dma_addr_t *dma_handle, void **ret)
 {
@@ -77,6 +87,9 @@ void *dma_alloc_coherent(struct device *dev, size_t size,
 	if (dev == NULL || (dev->coherent_dma_mask < 0xffffffff))
 		gfp |= GFP_DMA;
 
+	if (!dev)
+		dev = &fallback_dev;
+
 	dma_mask = dev->coherent_dma_mask;
 	if (dma_mask == 0)
 		dma_mask = DMA_32BIT_MASK;
-- 
1.5.0.6

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