RE: [PATCH rtw-next] wifi: rtw89: acpi: check for _DSM function support before evaluating it

[Ping-Ke Shih]

Rosen Penev <rosenp@xxxxxxxxx> wrote:
> When the WiFi device has no ACPI companion, or the firmware does not
> implement a given rtw89 _DSM function, rtw89_acpi_evaluate_dsm() calls
> acpi_evaluate_dsm() anyway. ACPI core then warns on every probe:
> 
>   ACPI: \: failed to evaluate _DSM e8c3a8d2-694b-004f-82bd-fe8607803aa7 rev:0 func:10 (0x1001)
>   ACPI: \: failed to evaluate _DSM e8c3a8d2-694b-004f-82bd-fe8607803aa7 rev:0 func:6 (0x1001)
> 
> Here the handle is NULL, and acpi_evaluate_object() returns
> AE_BAD_PARAMETER. All callers already treat failure as "no policy
> provided by the platform", so this is only noise.
> 
> Use acpi_check_dsm() first. It returns false for a NULL handle and for
> functions that are not advertised, so absent functions fail quietly at
> debug level, as rtw89_acpi_evaluate_method() already does.

The acpi_check_dsm() is to evaluate func 0 before actually accessing func. 
I'm not sure if all platforms will implement func 0. Do you know that?

> 
> Seen on an RTL8852BE in a desktop PCIe slot.
> 
> Fixes: e897b0bef38a ("wifi: rtw89: introduce realtek ACPI DSM method")

Does it need a Fixes? As I see, this is not a bug. 

> Signed-off-by: Rosen Penev <rosenp@xxxxxxxxx>