linux-kernel - Re: [PATCH] parport_pc: set properly the dma_mask for parport

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Date:	Wed, 17 Jun 2009 12:07:53 +0930
From:	Malcom Blaney <malcolm.blaney@...tek.com.au>
To:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Cc:	alan@...ux.intel.com, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] parport_pc: set properly the dma_mask for parport_pc 
	device

I used this with a patch I worked on a few years ago to fix ECP reads
from the parport.

If anyone is interested it can be found at:
http://lists.infradead.org/pipermail/linux-parport/2007-October/000614.html

2009/6/17 FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>:
> parport_pc_probe_port() creates the own 'parport_pc' device if the
> device argument is NULL. Then parport_pc_probe_port() doesn't
> initialize the dma_mask and coherent_dma_mask of the device and calls
> dma_alloc_coherent with it. dma_alloc_coherent fails because
> dma_alloc_coherent() doesn't accept the uninitialized dma_mask:
>
> http://lkml.org/lkml/2009/6/16/150
>
> Long ago, X86_32 and X86_64 had the own dma_alloc_coherent
> implementations; X86_32 accepted a device having dma_mask that is not
> initialized however X86_64 didn't. When we merged them, we chose to
> prohibit a device having dma_mask that is not initialized. I think
> that it's good to require drivers to set up dma_mask (and
> coherent_dma_mask) properly if the drivers want DMA.
>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
> Reported-by: Malcom Blaney <malcolm.blaney@...tek.com.au>
> Tested-by: Malcom Blaney <malcolm.blaney@...tek.com.au>
> Cc: stable@...nel.org
> ---
>  drivers/parport/parport_pc.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/parport/parport_pc.c b/drivers/parport/parport_pc.c
> index 151bf5b..1af57b7 100644
> --- a/drivers/parport/parport_pc.c
> +++ b/drivers/parport/parport_pc.c
> @@ -2271,6 +2271,9 @@ struct parport *parport_pc_probe_port(unsigned long int base,
>                if (IS_ERR(pdev))
>                        return NULL;
>                dev = &pdev->dev;
> +
> +               dev->coherent_dma_mask = DMA_BIT_MASK(24);
> +               dev->dma_mask = &dev->coherent_dma_mask;
>        }
>
>        ops = kmalloc(sizeof(struct parport_operations), GFP_KERNEL);
> --
> 1.6.0.6
>
>
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