linux-kernel - Re: [PATCH] ISA: set 24-bit dma

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Date:	Sat, 31 May 2008 10:56:17 +0200
From:	Takashi Iwai <tiwai@...e.de>
To:	Rene Herman <rene.herman@...access.nl>
Cc:	Andrew Morton <akpm@...l.org>,
	Bjorn Helgaas <bjorn.helgaas@...com>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	ALSA devel <alsa-devel@...a-project.org>
Subject: Re: [PATCH] ISA: set 24-bit dma_mask for ISA devices.

At Sat, 31 May 2008 01:55:52 +0200,
Rene Herman wrote:
> 
> >From 56e4b14aa58612aeb41b51d73a75f85dd72127a1 Mon Sep 17 00:00:00 2001
> From: Rene Herman <rene.herman@...il.com>
> Date: Sat, 31 May 2008 00:31:40 +0200
> Subject: [PATCH] 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@...il.com>
> Cc: Bjorn Helgaas <bjorn.helgaas@...com>
> Cc: Takashi Iwai <tiwai@...e.de>

Acked-by: Takashi Iwai <tiwai@...e.de>


Takashi

> Cc: Alan Cox <alan@...rguk.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) {
>  			put_device(&isa_dev->dev);
> -- 
> 1.5.2.2
> 
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