From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752695AbaEBUhS (ORCPT ); Fri, 2 May 2014 16:37:18 -0400 Received: from mail.mev.co.uk ([62.49.15.74]:58933 "EHLO mail.mev.co.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752197AbaEBUhQ (ORCPT ); Fri, 2 May 2014 16:37:16 -0400 Message-ID: <5363FF10.306@mev.co.uk> Date: Fri, 2 May 2014 21:24:48 +0100 From: Ian Abbott Organization: MEV Ltd User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Hartley Sweeten , Brilliantov Kirill Vladimirovich , Greg Kroah-Hartman CC: "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] staging/comedi: fix sparse warning: shift too big References: <1399042624-9441-1-git-send-email-brilliantov@inbox.ru> <5363CCAE.9000006@mev.co.uk> In-Reply-To: Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-ClientProxiedBy: MEVEXCHANGE.mev.local (10.0.0.4) To MEVEXCHANGE.mev.local (10.0.0.4) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 02/05/14 19:28, Hartley Sweeten wrote: > On Friday, May 02, 2014 9:50 AM, Ian Abbott wrote: >> On 2014-05-02 15:57, Brilliantov Kirill Vladimirovich wrote: >>> Signed-off-by: Brilliantov Kirill Vladimirovich >>> --- >>> drivers/staging/comedi/drivers/ni_stc.h | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/drivers/staging/comedi/drivers/ni_stc.h b/drivers/staging/comedi/drivers/ni_stc.h >>> index f0630b78..197b568 100644 >>> --- a/drivers/staging/comedi/drivers/ni_stc.h >>> +++ b/drivers/staging/comedi/drivers/ni_stc.h >>> @@ -717,7 +717,7 @@ enum AI_AO_Select_Bits { >>> static inline unsigned ni_stc_dma_channel_select_bitfield(unsigned channel) >>> { >>> if (channel < 4) >>> - return 1 << channel; >>> + return 1 << (channel & 0x3); >>> if (channel == 4) >>> return 0x3; >>> if (channel == 5) >>> >> >> The warning seems a bit spurious! > > The whole mite.c driver and it's users are all a bit of a mess. > > I did find the information about the "AI AO Select Register" in the National > Instruments PCI E Series manual: > > ----- > > The AI AO Select Register contains 8 bits that control the logical DMA selection for the > analog input and analog output resources. The contents of this register are cleared upon power > up and after a reset condition. > Address: base address + 0x09 > Type: write-only > Word size: 8-bit > > Bit Name Description > 7-4 Reserved Reserved-Always write 0 to these bits (for PCI-6032E > and PCI-6033E only). > 7-4 Output Analog Output Logical Channel D through A-These four > bits select the logical channels of the MITE to be used by > the analog output. You can only set one of these bits at a > time (except for the PCI-6032E and PCI-6033E). > 3-0 Input Analog Input Logical Channel D through A-These four > bits select the logical channels to be used by the analog > input. You can only set one of these bits at a time. > > ----- > > Based on this the ni_stc_dma_channel_select_bitfield() function appears to be > incorrect. The "channel"s should only be in the range 0 to 3 and result in a returned > bitfield of: > > channel bitfield Description > 0 0x01 Analog Input or Output Channel A > 1 0x02 Analog Input or Output Channel B > 2 0x04 Analog Input or Output Channel C > 3 0x08 Analog Input or Output Channel D > > Just my two cents... Apparently, the M-series cards have six DMA channels - two more than the E-series cards. They must have decided to keep the existing bitfield encoding for the first four channels for backwards compatibility, and use special bitfield values for the extra channels. -- -=( Ian Abbott @ MEV Ltd. E-mail: )=- -=( Tel: +44 (0)161 477 1898 FAX: +44 (0)161 718 3587 )=-