netdev - Re: [Uclinux-dist-devel] [PATCH v3] add the driver for Analog Devices Blackfin on-chip CAN controllers

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Date:	Thu, 10 Dec 2009 05:45:52 -0500
From:	Mike Frysinger <vapier.adi@...il.com>
To:	Wolfgang Grandegger <wg@...ndegger.com>
Cc:	Barry Song <21cnbao@...il.com>, socketcan-core@...ts.berlios.de,
	uclinux-dist-devel@...ckfin.uclinux.org, davem@...emloft.net,
	"H.J. Oertel" <oe@...t.de>, netdev@...r.kernel.org
Subject: Re: [Uclinux-dist-devel] [PATCH v3] add the driver for Analog Devices 
	Blackfin on-chip CAN controllers

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 <linux/module.h>
>>>> +#include <linux/init.h>
>>>> +#include <linux/kernel.h>
>>>> +#include <linux/types.h>
>>> 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

>>> 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.

at any rate, the common Blackfin I/O accessor functions force a lot of
useless overhead when used here as they're designed for async memory,
not MMRs.  the driver needs to be switched to the bfin_read/bfin_write
MMR functions.
-mike
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