linux-kernel - Re: [PATCH 2/2 v2] Driver core: reduce duplicated code

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Date:	Mon, 28 Jun 2010 13:27:25 +0800
From:	Eric Miao <eric.y.miao@...il.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Cc:	Sascha Hauer <s.hauer@...gutronix.de>, Greg KH <greg@...ah.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Dmitry Torokhov <dtor@...l.ru>,
	Anisse Astier <anisse@...ier.eu>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Magnus Damm <damm@...nsource.se>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Paul Mundt <lethal@...ux-sh.org>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2 v2] Driver core: reduce duplicated code

2010/6/28 Uwe Kleine-König <u.kleine-koenig@...gutronix.de>:
> Hi Eric,
>
> On Mon, Jun 28, 2010 at 12:55:45PM +0800, Eric Miao wrote:
>> I suggest you to have a look into arch/arm/mach-mmp/devices.c and
>> arch/arm/mach-mmp/pxa{168,910}.c as well as
>> arch/arm/mach-mmp/include/mach/pxa{168,910}.h, maybe we can find
>> some common practice.
> I think I like this approach in general, I already thought about not
> passing all parameters as function/macro arguments, too.  But maybe this
> becomes too excessive for imx as I would need too many of these device
> desc for the different imx variants?!
>
> Anyhow a few things I thought when looking in the files you suggested:
>
>  - Why not use an array for all uart devdescs, maybe the code for
>   pxa168_add_uart could become a bit smaller then?:
>
>        extern struct pxa_device_desc pxa168_device_uart[2];
>        ...
>        static inline int pxa168_add_uart(int id)
>        {
>                struct pxa_device_desc *d = pxa168_device_uart + id;
>
>                if (id < 0 || id > 2)
>                        return -EINVAL;
>
>                return pxa_register_device(d, NULL, 0);
>        }
>
>   (Ditto for the other types obviously.)

That's a good suggestion, yet it came that way for two reasons:

1. the initial naming mess, uart0 was later renamed to uart1, e.g.
2. and the restrictions of PXA{168,910}_DEVICE() macros, these
   macros are handy to simplify the definition, but may require fancy
   tricks to make it support array

>
>  - shouldn't all these pxa_device_descs and pxa168_add_$device functions
>   be __initdata and __init?
>

pxa{168,910}_add_device() are actually 'static inline' so my assumption
is they will be inlined when referenced, otherwise won't occupy any code
space. The *_descs, however, they are __initdata if you look into the
definitions of PXA{168,910}_DEVICES

>  - pxa_register_device is better than my add_resndata function in (at
>   least) one aspect as it sets coherent_dma_mask, too.  This is
>   something I missed when trying to add mxc-mmc (IIRC) devices.
>
> Thanks
> Uwe
>
> --
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
>
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