Re: is_device_dma_capable

[Malcom Blaney]

Thanks Fujita, your patch worked a treat!

2009/6/16 FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>:
> On Tue, 16 Jun 2009 17:53:03 +0930
> Malcom Blaney <malcolm.blaney@xxxxxxxxxxxxx> wrote:
>
>> Hi Fujita,
>>
>> 2009/6/16 FUJITA Tomonori <fujita.tomonori@xxxxxxxxxxxxx>:
>> > You use X86_32, right?
>>
>> I have CONFIG_X86_32=y in my config file.
>>
>> >
>> > In 2.6.25, 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, I think.
>> >
>> > When we merged them, we chose to prohibit a device having dma_mask
>> > that is not initialized. I'm not sure the DMA docs say this but IMO
>> > it's good to require drivers to set up dma_mask (and
>> > coherent_dma_mask) properly if the drivers want DMA.
>> >
>>
>> If you could point me in the direction of how to set these values
>> correctly, I would appreciate it.
>
> You hit the problem that a device that parport_pc_probe_port creates
> but doesn't set up the dma_mask properly, right (I'm not familiar with
> the driver at all so I might misunderstand something)?
>
> If so, I guess that the following patch works (only compile tested).
>
>
> 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);
>
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/