isa: set 24-bit dma_mask for ISA devices

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@gmail.com>
Cc: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 0 deletions

diff --git a/drivers/base/isa.c b/drivers/base/isa.c
index d2222397a40..efd57757494 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) {
                         put_device(&isa_dev->dev);