From: Tabi Timur-B04825 <B04825@freescale.com>
To: Dan Malek <ppc6dev@digitaldans.com>
Cc: "linuxppc-dev@lists.ozlabs.org" <linuxppc-dev@lists.ozlabs.org>
Subject: Re: minimum guaranteed alignment of dma_alloc_coherent?
Date: Sat, 5 Feb 2011 02:04:40 +0000 [thread overview]
Message-ID: <4D4CB038.9020602@freescale.com> (raw)
In-Reply-To: <2A5A3DDA-94B3-48E3-9E49-6A5260BE1484@digitaldans.com>
Dan Malek wrote:
>
>
>> On a side note, do I really need to pass GFP_DMA ....
>
> The GFP_DMA is architecture dependent. Are you writing
> a driver to be used across multiple architectures?
It's conceivable that the driver could work on PowerPC and ARM.
> If it's
> necessary, I'd document why you are using it (an ISA device
> on x86 for example) and then let other architectures
> determine if it's necessary for them.
I guess I'm not clear. I was wondering why an API called "dma_alloc_cohere=
nt" (that has the word "dma" in it) needs to be told to allocate DMA-safe m=
emory. When would it make sense to call dma_alloc_cohernet without GFP_DMA=
? If you don't want DMA-able memory, then you shouldn't be calling dma_all=
oc_anything.
--=20
Timur Tabi
Linux kernel developer=
next prev parent reply other threads:[~2011-02-05 2:05 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-05 0:14 minimum guaranteed alignment of dma_alloc_coherent? Timur Tabi
2011-02-05 1:09 ` Dan Malek
2011-02-05 2:04 ` Tabi Timur-B04825 [this message]
2011-02-05 2:56 ` Dan Malek
2011-02-07 15:13 ` Timur Tabi
2011-03-29 0:32 ` Benjamin Herrenschmidt
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