Date: Wed, 1 Feb 2006 17:32:54 +1100 From: Peter Jeremy <peterjeremy@optushome.com.au> To: Ian Dowse <iedowse@iedowse.com> Cc: Juergen Lock <nox@jelal.kn-bremen.de>, freebsd-usb@freebsd.org Subject: Re: cvs commit: src/sys/dev/usb ehci.c ehci_pci.c ehcivar.h Message-ID: <20060201063254.GD678@turion.vk2pj.dyndns.org> In-Reply-To: <200601312200.aa58422@nowhere.iedowse.com> References: <20060131194244.GA75983@saturn.kn-bremen.de> <200601312200.aa58422@nowhere.iedowse.com>
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On Tue, 2006-Jan-31 22:00:21 +0000, Ian Dowse wrote: >In the case of USB, there is actually no need for it to perform >large contiguous allocations because the host controllers all support >some limited scatter-gather functionality so they can mostly access >the caller's memory buffer directly via bus_dmamap_load(). This is >something I implemented a year or to ago but I haven't got around >to finishing the last few details of the patch yet. I'd looked into the specs far enough to determine that this was possible but haven't looked at how difficult it would be to implement it. I think this is a preferable solution and would be interested in helping you finish your patch. Whilst it's desirable that contigmalloc() not panic, making contigmalloc() return NULL when asked to allocate a large block of memory without waiting doesn't actually help get the data from the physical device into the driver. -- Peter Jeremy
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