linux-kernel - Re: 2nd attempt: help with dma_alloc_coherent() + dma_free

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Message-ID: <CA+55aFyEE6pM2gVfgd3xjQR5rF6ij5pG7BXjkH+C5aHbxAk6mg@mail.gmail.com>
Date:	Tue, 8 Jan 2013 09:24:11 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jeff Chua <jeff.chua.linux@...il.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jonathan Corbet <corbet@....net>
Subject: Re: 2nd attempt: help with dma_alloc_coherent() + dma_free_coherent()

On Tue, Jan 8, 2013 at 9:17 AM, Jeff Chua <jeff.chua.linux@...il.com> wrote:
>
> Interesting, but there are 54 lines under the kernel directories that
> use "dma_alloc_coherent(NULL," followed by "dma_free_coherent(NULL,"

As mentioned, it works on some platforms. That doesn't make it right.

> So, shouldn't they be fixed as well? ... unless they are so old that
> nobody cares anymore ...

Some of the ones I saw are in MIPS or blackfin. Others probably *are*
so old that nobody cares, and happen to work because there's iommu's
or other things that simply don't care about the device.

> # find . -exec grep -H "dma_alloc_coherent(NULL" {} \; | wc -l
> 54
>
> #find . -exec grep -H "dma_free_coherent(NULL" {} \; | wc -l
> 72

Let me tell you about "git grep", so that you never need to do that
disgusting "find -exec grep" ever again.

It does threading, it's fast, and it just works.

                Linus
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