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SubjectRe: [PATCH v5 03/18] ACPI / table: Count matched and successfully parsed entries without specifying max entries
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 <tomasz.nowicki@linaro.org>
>>
>> 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 <grant.likely@linaro.org>
>> Signed-off-by: Tomasz Nowicki <tomasz.nowicki@linaro.org>
>> Signed-off-by: Hanjun Guo <hanjun.guo@linaro.org>
>> ---
>> 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.
>>
>


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