[PATCH] ACPI/IORT: fix IORT Reserved Memory Range node mapping error

[guanghui.fgh]

在 2023/7/17 16:48, Marc Zyngier 写道:
> On 2023-07-17 09:38, Guanghui Feng wrote:
>> In the ARM IORT specifications DEN 0049E.d, the recommended ID mapping 
>> format：
>> Field        Note Description
>> --------------------------------
>> Input base    The lowest value in the input range
>> Number of IDs    The number of IDs in the range "minus" one
>>
>> When there is only one id mapping in the Reserved Memory Range
>> (RMR) node, the node filed: "Number of IDs" is zero and
>> iort_node_get_rmr_info will not analyse id mapping. This is
>> not in compliance with the regulations.
>>
>> Signed-off-by: Guanghui Feng <guanghuifeng at linux.alibaba.com>
>> ---
>>  drivers/acpi/arm64/iort.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/acpi/arm64/iort.c b/drivers/acpi/arm64/iort.c
>> index 3631230..8427cc3 100644
>> --- a/drivers/acpi/arm64/iort.c
>> +++ b/drivers/acpi/arm64/iort.c
>> @@ -1007,7 +1007,7 @@ static void iort_node_get_rmr_info(struct
>> acpi_iort_node *node,
>>      for (i = 0; i < node->mapping_count; i++, map++) {
>>          struct acpi_iort_node *parent;
>>
>> -        if (!map->id_count)
>> +        if (!(map->id_count + 1))
>>              continue;
> 
> struct acpi_iort_id_mapping {
> [...]
>      u32 id_count;        /* Number of IDs */
> [...]
> };
> 
> So the only way for id_count+1 to be 0 is when id_count==~0,
> making the check even more buggy than it currently is.
> 
>          M.
Thanks for your response.

It's true. Maybe we should use (id_count == 0xffffffff) or
(id_count == u32(-1)) to check the mapping count.
How about this?