[PATCH] ISA: set 24-bit dma_mask for ISA devices.

Rene Herman rene.herman at gmail.com
Sat May 31 00:31:40 CEST 2008

dma_alloc_coherent() on x86 currently takes a passed in NULL device
pointer to mean that it should allocate an ISA compatible (24-bit)
buffer which is a bit of a hack.

The ALSA ISA drivers are the main consumers of this but have a struct
device in fact readily available.

For the legacy drivers, this sets the device dma_mask in preparation
for using the actual device with the DMA API so as to eventually not
need the NULL hack in dma_alloc_coherent().

This does not fix a current bug -- 2.6.26-rc1 stumbled over the NULL
hack in dma_alloc_coherent() but this has already been fixed in commit
4a367f3a9dbf2e7ffcee4702203479809236ee6e by Takashi Iwai.

Signed-off-by: Rene Herman <rene.herman at gmail.com>
Cc: Bjorn Helgaas <bjorn.helgaas at hp.com>
Cc: Takashi Iwai <tiwai at suse.de>
Cc: Alan Cox <alan at lxorguk.ukuu.org.uk>
 drivers/base/isa.c |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/drivers/base/isa.c b/drivers/base/isa.c
index d222239..efd5775 100644
--- a/drivers/base/isa.c
+++ b/drivers/base/isa.c
@@ -7,6 +7,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/init.h>
+#include <linux/dma-mapping.h>
 #include <linux/isa.h>
 static struct device isa_bus = {
@@ -141,6 +142,9 @@ int isa_register_driver(struct isa_driver *isa_driver, unsigned int ndev)
 		isa_dev->dev.release		= isa_dev_release;
 		isa_dev->id			= id;
+		isa_dev->dev.coherent_dma_mask = DMA_24BIT_MASK;
+		isa_dev->dev.dma_mask = &isa_dev->dev.coherent_dma_mask;
 		error = device_register(&isa_dev->dev);
 		if (error) {

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