Re: [ANNOUNCE][PATCH 2.6.11 2/3] megaraid_sas: Announcing new mod ule for LSI Logic's SAS based MegaRAID controllers

From: 'Christoph Hellwig' (hch_at_infradead.org)
Date: 03/09/05

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    Date:	Wed, 9 Mar 2005 22:59:27 +0000
To: "Bagalkote, Sreenivas" <sreenib@lsil.com>

    On Wed, Mar 09, 2005 at 05:47:27PM -0500, Bagalkote, Sreenivas wrote:
    > >
    > >Even for kernels with a 64bit dma_addr_t you can get 32bit dma
    > >addresses
    > >only. As a start check whether the pci_set_dma_mask for the 64bit mask
    > >failed - in that case you can always use 32bit SGLs.
    > >
    >
    > Please help me understand: If dma_addr_t is 64 bit, I will get 64bit
    > addresses in scatterlist regardless the outcome of pci_set_dma_mask,
    > won't I? These addresses may have valid or null high addresses. My idea
    > was to have 32(64) bit SGLs for 32(64) bit dma_addr_t.

    if pci_set_dma_mask for the 64bit mask fails the upper 32bit bit of
    dma_addr_t will guaranteed to be zero, so you don't need to take them
    into account for your hardware SGL.

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