Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262529AbVCJAD0 (ORCPT ); Wed, 9 Mar 2005 19:03:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262387AbVCIX7g (ORCPT ); Wed, 9 Mar 2005 18:59:36 -0500 Received: from mail0.lsil.com ([147.145.40.20]:3794 "EHLO mail0.lsil.com") by vger.kernel.org with ESMTP id S262065AbVCIX4w (ORCPT ); Wed, 9 Mar 2005 18:56:52 -0500 Message-ID: <0E3FA95632D6D047BA649F95DAB60E570230CC23@exa-atlanta> From: "Bagalkote, Sreenivas" To: "'Christoph Hellwig'" Cc: "'Arjan van de Ven'" , "'linux-kernel@vger.kernel.org'" , "'linux-scsi@vger.kernel.org'" , "'James Bottomley'" , "'Matt_Domsch@Dell.com'" , Andrew Morton Subject: RE: [ANNOUNCE][PATCH 2.6.11 2/3] megaraid_sas: Announcing new mod ule for LSI Logic's SAS based MegaRAID controllers Date: Wed, 9 Mar 2005 18:56:02 -0500 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2657.72) Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1259 Lines: 33 >> > >> >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. > Okay. I understood. Thanks. But please consider this also: Arjan pointed out that by basing my 32/64 SGL decision solely on #define IS_DMA64 sizeof(dma_addr_t)==8, I can rely on gcc to optimize the unused portion of the code away. If I take pci_set_dma_mask also into account, I can't do that, can I? Thanks, Sreenivas - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/