Return-path: Received: from mail-bw0-f21.google.com ([209.85.218.21]:43628 "EHLO mail-bw0-f21.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755518AbYLSSRi (ORCPT ); Fri, 19 Dec 2008 13:17:38 -0500 Received: by bwz14 with SMTP id 14so4125445bwz.13 for ; Fri, 19 Dec 2008 10:17:36 -0800 (PST) Message-ID: <45e8e6c40812191017w799e04b7m4815caab94818766@mail.gmail.com> (sfid-20081219_191806_410132_AB04448E) Date: Fri, 19 Dec 2008 10:17:36 -0800 From: "Andrey Yurovsky" To: "Peter Wippich" Subject: Re: [PATCH 3/3] libertas: if_spi, driver for libertas GSPI devices Cc: "Harald Welte" , linux-wireless@vger.kernel.org, "Colin McCabe" , "Stefan Schmidt" , libertas-dev@lists.infradead.org In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 References: <1229398052-27465-1-git-send-email-colin@cozybit.com> <1229398052-27465-2-git-send-email-colin@cozybit.com> <1229398052-27465-3-git-send-email-colin@cozybit.com> <1229398052-27465-4-git-send-email-colin@cozybit.com> <20081219160836.GQ9285@prithivi.gnumonks.org> <45e8e6c40812190831k7796e240w55c47d7ca6417437@mail.gmail.com> Sender: linux-wireless-owner@vger.kernel.org List-ID: Thanks Peter. The Blackfin SPI controller provides built-in Chip Select signals and one can choose to assign one of several CS lines to a device. However we need a GPIO-style CS rather than one generated by the controller and while I see that there's certainly room to implement that in the SPI controller driver, I don't see a way to have both that and the automatically-generated CS as options. That is, if I understand correctly, there's no way to configure spi_board_info with, say, a flag that tells the driver "hey, use this specific GPIO line", instead you can pick between 0 and num_chipselect for your chip_select value and, in Blackfin's case, this would configure one of the automatically-generated lines. We appreciate additional feedback about this. Thanks, On Fri, Dec 19, 2008 at 8:57 AM, Peter Wippich wrote: > > Hi Andrey, > >> The '8686 requires us to assert CS# and then hold it asserted for the >> entire transaction. The transaction is an arbitrary number of SPI >> transfers. Most host controllers cannot do this (they'll toggle CS# >> between individual transactions) and therefore we chose to not use the >> controller CS# line and use a GPIO. Can you suggest a different way >> to do this given the current SPI framework? > > This can be handled by the SPI driver. See pxa2xx_spi.c as an example. > Look for cs_control() to get the picture..... > Perhaps this should go to the general driver and not be handled by the > chip specific code. Seems a problem general enough. > > Chears, > > Peter > -- Andrey Yurovsky cozybit Inc.