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Date: Thu, 20 Mar 2008 12:29:22 -0500 (CDT)
From: Mark Tinguely <tinguely@casselton.net>
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To: freebsd-questions@freebsd.org, yonyossef.lists@gmail.com
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Cc: 
Subject: Re: bus_dmamem_alloc
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>  so I'm running:
>
>  err =
>  bus_dmamem_alloc(ring->dma_tag, &ring->buf,
>  BUS_DMA_NOWAIT|BUS_DMA_ALLOCNOW, &ring->dma_map);
>
>  but after calling bus_dmamem_allloc the dma_map variable is still NULL. is
>  this OK?

Sure, you are allocating with BUS_DMA_NOWAIT. err is probably equal to ENOMEM.

If allocation size is larger than a PAGE_SIZE or specific alignment is
require then contigmalloc() is called to satisfy the allocation.
contigmalloc() can fail even when specifying WAITOK.

--Mark Tinguely.