Re: [PATCH v4] platform/x86: alienware-wmi-base: Transition to new WMI API

Armin Wolf
2026-04-29T21:19:53Z

Am 29.04.26 um 15:23 schrieb Kurt Borja:

> On Tue Apr 28, 2026 at 2:27 PM -05, Armin Wolf wrote:
>> Am 28.04.26 um 18:37 schrieb Kurt Borja:
>>
>>> Transition to the new wmi_buffer based WMI API.
>>>
>>> Signed-off-by: Kurt Borja <kuurtb@gmail.com>
>>> ---
>>> v4:
>>> - Rebase to use the new wmidev_invoke_method() with size check
>>>
>>> v3: https://patch.msgid.link/20260331-aw-new-api-v3-1-ef03b94529d8@gmail.com
>>> - Use __free() instead of manual cleanup.
>>> - Include <linux/types.h>
>>>
>>> v2: https://patch.msgid.link/20260331-aw-new-api-v2-1-3b0d33bf8d22@gmail.com
>>> - Cast wmi_buffer data to __le32 and then use le32_to_cpu() before
>>> returning
>>>
>>> v1: https://patch.msgid.link/20260330-aw-new-api-v1-1-95910bfa1b38@gmail.com
>>> ---
>>> drivers/platform/x86/dell/alienware-wmi-base.c | 31 ++++++++++++++++----------
>>> 1 file changed, 19 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/drivers/platform/x86/dell/alienware-wmi-base.c b/drivers/platform/x86/dell/alienware-wmi-base.c
>>> index 64562b92314f..21d3acfbd73d 100644
>>> --- a/drivers/platform/x86/dell/alienware-wmi-base.c
>>> +++ b/drivers/platform/x86/dell/alienware-wmi-base.c
>>> @@ -12,8 +12,13 @@
>>> #include <linux/cleanup.h>
>>> #include <linux/module.h>
>>> #include <linux/platform_device.h>
>>> +#include <linux/slab.h>
>>> +#include <linux/types.h>
>>> #include <linux/dmi.h>
>>> #include <linux/leds.h>
>>> +
>>> +#include <asm/byteorder.h>
>>> +
>>> #include "alienware-wmi.h"
>>>
>>> MODULE_AUTHOR("Mario Limonciello <mario.limonciello@outlook.com>");
>>> @@ -150,21 +155,23 @@ u8 alienware_interface;
>>> int alienware_wmi_command(struct wmi_device *wdev, u32 method_id,
>>> void *in_args, size_t in_size, u32 *out_data)
>>> {
>>> - struct acpi_buffer out = {ACPI_ALLOCATE_BUFFER, NULL};
>>> - struct acpi_buffer in = {in_size, in_args};
>>> - acpi_status ret;
>>> + struct wmi_buffer out, in = {
>>> + .data = in_args,
>>> + .length = in_size,
>>> + };
>>> + int ret;
>>>
>>> - ret = wmidev_evaluate_method(wdev, 0, method_id, &in, out_data ? &out : NULL);
>>> - if (ACPI_FAILURE(ret))
>>> - return -EIO;
>>> -
>>> - union acpi_object *obj __free(kfree) = out.pointer;
>>> + if (out_data)
>>> + ret = wmidev_invoke_method(wdev, 0, method_id, &in, &out,
>>> + sizeof(*out_data));
>>> + else
>>> + ret = wmidev_invoke_method(wdev, 0, method_id, &in, NULL, 0);
>>> + if (ret)
>>> + return ret;
>>>
>>> if (out_data) {
>>> - if (obj && obj->type == ACPI_TYPE_INTEGER)
>>> - *out_data = (u32)obj->integer.value;
>>> - else
>>> - return -ENOMSG;
>>> + __le32 *data __free(kfree) = out.data;
>>> + *out_data = le32_to_cpu(*data);
>>> }
>> Hi,
>>
>> calling wmidev_invoke_method() with a NULL output buffer will likely lead to crashes. This happens
>> because wmidev_invoke_method() demands that a valid pointer to a output buffer is provided by the
>> caller. I suggest that you use wmidev_invoke_procedure() instead:
>>
>> __le32 *data __free(kfree) = NULL;
>>
>> if (!out_data)
>> return wmidev_invoke_procedure(wdev, 0, method_id, &in);
>>
>> ret = wmidev_invoke_method(wdev, 0, method_id, &in, &out, sizeof(*data));
>> if (ret < 0)
>> return ret;
>>
>> result = out.data
>> ...
> Hi Armin,
>
> You're right, I thought the only difference between _procedure and
> _method was the size check.
>
> Also, Sashiko [1] reported that out.data might be ZERO_SIZE_PTR even if
> wmidev_invoke_method() succeeds. I thought it was a false positive but I
> looked further and it was actually a bug. I submitted a fix for this.

Thank you, i will take a look at it immediately.

Thanks,
Armin Wolf

>
> [1] https://sashiko.dev/#/patchset/20260428-aw-new-api-v4-1-d2c06241d7ad%40gmail.com
>