From: Robert Hancock <hancockr@shaw.ca>
To: linux-kernel@vger.kernel.org
Cc: linux-usb@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] USB: use stack allocation for struct usb_ctrlrequest
Date: Wed, 10 Dec 2008 18:59:34 -0600 [thread overview]
Message-ID: <494065F6.3010602@shaw.ca> (raw)
In-Reply-To: <20081210142301.GA11490@localhost>
Wu Fengguang wrote:
>> In many cases there is no problem to DMA high memory. If you happen to
>> be working with a device that does have problems with full 32 bit
>> addresses then GFP_DMA would be the right flag, not GFP_NOIO.
>
> For 64bit systems, we can easily go beyond 4GB physical memory.
> So at least we should add GFP_DMA32 in addition to GFP_NOIO?
No. The DMA mapping API handles either setting up the IOMMU or doing
software bounce buffering to handle the DMA transfer regardless of where
the memory is located, so drivers don't need to mess with GFP_DMA32.
prev parent reply other threads:[~2008-12-11 1:00 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-12-10 7:32 [PATCH] USB: use stack allocation for struct usb_ctrlrequest Wu Fengguang
2008-12-10 9:40 ` Laurent Pinchart
2008-12-10 12:43 ` Wu Fengguang
2008-12-10 14:07 ` Gilad Ben-Yossef
2008-12-10 14:23 ` Wu Fengguang
2008-12-10 14:31 ` Gilad Ben-Yossef
2008-12-11 0:01 ` Pete Zaitcev
2008-12-11 0:57 ` Robert Hancock
2008-12-11 0:59 ` Robert Hancock [this message]
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