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@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

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 0d630ae3d910..0600a37ba835 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)
 {
@@ -75,6 +85,9 @@ 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;
+
         page = dma_alloc_pages(dev, gfp, order);
         if (page == NULL)
                 return NULL;