From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wolfgang Grandegger Subject: Re: [Uclinux-dist-devel] [PATCH v3] add the driver for Analog Devices Blackfin on-chip CAN controllers Date: Thu, 10 Dec 2009 12:16:17 +0100 Message-ID: <4B20D881.3090003@grandegger.com> References: <1260430072-21106-1-git-send-email-21cnbao@gmail.com> <4B20BB36.50509@grandegger.com> <8bd0f97a0912100204gd2b09f6r2799d9f951d6b9e1@mail.gmail.com> <4B20CB82.6060702@grandegger.com> <8bd0f97a0912100245k9930c90ke4b184da68a9f958@mail.gmail.com> <4B20D39C.6030103@grandegger.com> <8bd0f97a0912100304p16087688q681710ba6b152c0c@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Barry Song <21cnbao@gmail.com>, socketcan-core@lists.berlios.de, uclinux-dist-devel@blackfin.uclinux.org, davem@davemloft.net, "H.J. Oertel" , netdev@vger.kernel.org To: Mike Frysinger Return-path: Received: from mail-out.m-online.net ([212.18.0.9]:39625 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760631AbZLJLQ5 (ORCPT ); Thu, 10 Dec 2009 06:16:57 -0500 In-Reply-To: <8bd0f97a0912100304p16087688q681710ba6b152c0c@mail.gmail.com> Sender: netdev-owner@vger.kernel.org List-ID: Mike Frysinger wrote: > On Thu, Dec 10, 2009 at 05:55, Wolfgang Grandegger wrote: >> Mike Frysinger wrote: >>> On Thu, Dec 10, 2009 at 05:20, Wolfgang Grandegger wrote: >>>> Mike Frysinger wrote: >>>>> On Thu, Dec 10, 2009 at 04:11, Wolfgang Grandegger wrote: >>>>>> Barry Song wrote: >>>>>>> +#include >>>>>>> +#include >>>>>>> +#include >>>>>>> +#include >>>>>> I think you don't need "types.h" as the code no longer uses "uint*_t". >>>>> linux/types.h declares all types, like u* which this driver still uses >>>> I just remember that "linux/types.h" needs to be added for the uint*_t >>>> types. At a first glance I do not see __u8/u8 being defined in that >>>> header file but I might have missed something. >>> you need to follow the include paths >> I thought I did. Could you point me to the relevant location? > > make kernel/printk.i > sed -n -e '/^#/p' -e '/ u64;/{p;q}' kernel/printk.i > linux/types.h -> asm/types.h -> asm-generic/types.h -> asm-generic/int-ll64.h Thanks. >>>>>> Well, I'm still not a friend of the following inline functions, >>>>>> especially the *one-liners* which are called just *once*. With the usage >>>>>> of structs they seem even more useless. >>>>> seems like it would make more sense to not even use the read/write >>>>> functions either. just declare the regs as volatile and assign/read >>>>> the struct directly. >>>> Two times no. Don't use volatile and proper accessor functions. See: >>>> >>>> http://lxr.linux.no/#linux+v2.6.32/Documentation/volatile-considered-harmful.txt >>> too bad the document is largely irrelevant (all but one paragraph) >>> because this is how volatiles were designed in the first place -- >>> hardware I/O registers. the CAN implementation here is Blackfin >>> specific and not going to be use elsewhere, so other architectures are >>> irrelevant. the resulting C code would certainly look a hell of a lot >>> more natural without the useless I/O accessor functions, and be much >>> tighter. >> Well, so far *no* volatiles have been used in the BFIN CAN driver. But >> if you tell me that they are really required for blackfin... I can't >> really judge. > > i'm not saying they're needed all the time, i'm saying volatile > produces more natural coding style than I/O accessors. but after > reviewing the bfin_read/bfin_write functions, we still need to use > those to workaround a simple anomaly on older parts. I believe that it's good practice to hide such details by using proper accessor functions. Wolfgang.