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

[Marc Zyngier]

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.
-- 
Who you jivin' with that Cosmik Debris?