Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754591Ab1FIS6a (ORCPT ); Thu, 9 Jun 2011 14:58:30 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:35015 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751481Ab1FIS61 convert rfc822-to-8bit (ORCPT ); Thu, 9 Jun 2011 14:58:27 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=FL9Wc1Qh/gewFHc3V+EzUTICHTBmlbVDpyWGVXIPOyOete/sgct1v9udzqGnNH+qMM E2U659xkvYRjIvkog58N0JuAbGUisBHqNUsG5yddgeh/g030n2FjYVH+NN+NEHuIgYff 0m8VhQWHgl4nJmJwgZ2xY2CwnItxm8U4ocbwQ= MIME-Version: 1.0 In-Reply-To: References: Date: Fri, 10 Jun 2011 00:28:25 +0530 Message-ID: Subject: Re: [RFC] dmaengine: add new api for preparing simple slave transfer From: Jassi Brar To: "Raju, Sundaram" Cc: "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "davinci-linux-open-source@linux.davincidsp.com" , "linux-omap@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2553 Lines: 44 On Thu, Jun 9, 2011 at 6:09 PM, Raju, Sundaram wrote: > Generic buffer description: > A generic buffer can be split into number of frames which contain number of chunks inside them. The frames need not be contiguous, nor do the chunks inside a frame. > >        ------------------------------------------------------------------- >        | Chunk 0 |ICG| Chunk 1 |ICG| ... |ICG| Chunk n |       Frame 0 >        ------------------------------------------------------------------- >        |                       Inter Frame Gap                     | >        ------------------------------------------------------------------- >        | Chunk 0 |ICG| Chunk 1 |ICG| ... |ICG| Chunk n |       Frame 1 >        ------------------------------------------------------------------- >        |                       Inter Frame Gap                     | >        ------------------------------------------------------------------- >        |                               ........                                    | >        ------------------------------------------------------------------- >        |                       Inter Frame Gap                     | >        ------------------------------------------------------------------- >        | Chunk 0 |ICG| Chunk 1 |ICG| ... |ICG| Chunk n |       Frame m >        ------------------------------------------------------------------- IIUC the above figure, the work done by DMA controller remains the same, either by passing this as a transfer of the new type or as a normal sg-list - unless the DMAC driver attempts to reorder the transfers or the DMAC h/w natively supports some form of sg-list. For DMACs, that have no special support, different representation wouldn't make a difference. And if the DMAC does support the kind of fancy scatter-gather, it should be possible for the dma api driver to analyze the submitted 'normal' sg-list and program the transfers at one go. Besides, it should be possible to have a 'template' sequence of requests prepared already because usually, for above mentioned scenario, the parameters don't change across items in a list. -- 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/