Subject: [PATCH v5 03/18] ACPI / table: Count matched and successfully parsed entries without specifying max entries

From: [email-masked] (Tomasz Nowicki)
Date: Mon, 24 Nov 2014 09:34:24 +0100

On 24.11.2014 02:45, Rafael J. Wysocki wrote:
> On Friday, October 17, 2014 09:36:59 PM Hanjun Guo wrote:
>> From: Tomasz Nowicki <[email-masked]>
>>
>> It is very useful to traverse all available table entries without max
>> number of expected entries type. Current acpi_parse_entries()
>> implementation gives that feature but it does not count those entries,
>> it returns 0 instead, so fix it to count matched and successfully
>> entries and return it.
>
> Hmm.  I guess that the goal is for count to only be incremented when the
> condition is satisfied entirely, while without the patch it may be incremented
> even if that isn't the case.

That would be our goal if patch would look like:
-		    && (!max_entries || count++ < max_entries))
+		    && (!max_entries && count++ < max_entries)) {
but then we can not walk through all available entries (with max_entries==0)

>
> I'm not sure how that is related to the above paragraph, however.
>

Previous changelog is not clear, let me rewrite it:

acpi_parse_entries() allows to traverse all available table entries (aka 
subtables) by passing max_entries parameter equal to 0. But for that use 
case acpi_parse_entries() does not inform caller how many entries were 
matched and for how many entries handler was run against. That patch is 
going to fix it.

Regards,
Tomasz

>> NOTE: This change has no impact to x86 and ia64 archs since existing code
>> checks for error occurrence only (acpi_parse_entries(...,0) < 0).
>>
>> Acked-by: Grant Likely <[email-masked]>
>> Signed-off-by: Tomasz Nowicki <[email-masked]>
>> Signed-off-by: Hanjun Guo <[email-masked]>
>> ---
>>   drivers/acpi/tables.c |    5 ++++-
>>   1 file changed, 4 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/tables.c b/drivers/acpi/tables.c
>> index 21ae521..b18e45e 100644
>> --- a/drivers/acpi/tables.c
>> +++ b/drivers/acpi/tables.c
>> @@ -225,10 +225,13 @@ acpi_parse_entries(unsigned long table_size,
>>   	while (((unsigned long)entry) + sizeof(struct acpi_subtable_header) <
>>   	       table_end) {
>>   		if (entry->type == entry_id
>> -		    && (!max_entries || count++ < max_entries))
>> +		    && (!max_entries || count < max_entries)) {
>>   			if (handler(entry, table_end))
>>   				return -EINVAL;
>>
>> +			count++;
>> +		}
>> +
>>   		/*
>>   		 * If entry->length is 0, break from this loop to avoid
>>   		 * infinite loop.
>>
>