linux-kernel - Re: [PATCH 2.6.20] isdn-capi: Use ARRAY

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Date:	Thu, 08 Feb 2007 10:53:10 -0500
From:	Bill Davidsen <davidsen@....com>
To:	Philippe De Muyter <phdm@...qel.be>
CC:	"Ahmed S. Darwish" <darwish.07@...il.com>,
	Joe Perches <joe@...ches.com>, kkeil@...e.de,
	kai.germaschewski@....de, linux-kernel@...r.kernel.org,
	isdn4linux@...tserv.isdn4linux.de
Subject: Re: [PATCH 2.6.20] isdn-capi: Use ARRAY_SIZE macro when appropriate

Philippe De Muyter wrote:
> On Tue, Feb 06, 2007 at 10:41:30PM +0200, Ahmed S. Darwish wrote:
>> On Tue, Feb 06, 2007 at 09:52:17AM -0800, Joe Perches wrote:
>>> On Tue, 2007-02-06 at 18:04 +0200, Ahmed S. Darwish wrote:
>>>> A patch to use ARRAY_SIZE macro already defined in kernel.h
>>>> Signed-off-by: Ahmed S. Darwish <darwish.07@...il.com>
>> [...]
>>>> -    int nelem = sizeof(procfsentries)/sizeof(procfsentries[0]);
>>>> +    int nelem = ARRAY_SIZE(procfsentries);
>>>>      int i;
>>>>  
>>>>      for (i=0; i < nelem; i++) {
>>> For these patches, perhaps you can eliminate the temporary
>>> variable and change the loop to the more common form of
>>>
>>> 	for (i = 0; i < ARRAY_SIZE(array); i++) {
>> Thanks, I think it's better too. Here's the modified patch.
>>
>> A patch to use ARRAY_SIZE macro when appropriate.
>>
>> Signed-off-by: Ahmed S. Darwish <darwish.07@...il.com>
>> ---
>> diff --git a/drivers/isdn/capi/capi.c b/drivers/isdn/capi/capi.c
>> index d22c022..87fe89c 100644
>> --- a/drivers/isdn/capi/capi.c
>> +++ b/drivers/isdn/capi/capi.c
>> @@ -1456,10 +1456,9 @@ static struct procfsentries {
>>  
>>  static void __init proc_init(void)
>>  {
>> -    int nelem = sizeof(procfsentries)/sizeof(procfsentries[0]);
>>      int i;
>>  
>> -    for (i=0; i < nelem; i++) {
>> +    for (i = 0; i < ARRAY_SIZE(procfsentries); i++) {
>>          struct procfsentries *p = procfsentries + i;
>>  	p->procent = create_proc_entry(p->name, p->mode, NULL);
>>  	if (p->procent) p->procent->read_proc = p->read_proc;
>> @@ -1468,10 +1467,9 @@ static void __init proc_init(void)
>>  
>>  static void __exit proc_exit(void)
>>  {
>> -    int nelem = sizeof(procfsentries)/sizeof(procfsentries[0]);
>>      int i;
>>  
>> -    for (i=nelem-1; i >= 0; i--) {
>> +    for (i = ARRAY_SIZE(procfsentries) - 1; i >= 0; i--) {
> 
> I would write such decrementing loops as :
> 
>        for (i = ARRAY_SIZE(procfsentries); --i >= 0; ) {
> 
> Long time ago, that produced better code.  I did not check recently though.

Why would you write "--i >= 0" instead of just "i--"? The size of an 
array can't be negative.

-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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