Re: [PATCH v3 1/9] platform/x86: dell-descriptor: Use new buffer-based WMI API

Armin Wolf
2026-03-31T20:00:43Z

Am 31.03.26 um 11:44 schrieb Ilpo Järvinen:

> On Sat, 14 Mar 2026, Armin Wolf wrote:
>
>> Use the new buffer-based WMI API to also support ACPI firmware
>> implementations that do not use ACPI buffers for the descriptor.
>>
>> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
>> ---
>> .../platform/x86/dell/dell-wmi-descriptor.c | 94 +++++++++----------
>> 1 file changed, 47 insertions(+), 47 deletions(-)
>>
>> diff --git a/drivers/platform/x86/dell/dell-wmi-descriptor.c b/drivers/platform/x86/dell/dell-wmi-descriptor.c
>> index c2a180202719..fe42eb8bbd79 100644
>> --- a/drivers/platform/x86/dell/dell-wmi-descriptor.c
>> +++ b/drivers/platform/x86/dell/dell-wmi-descriptor.c
>> @@ -7,7 +7,7 @@
>>
>> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>>
>> -#include <linux/acpi.h>
>> +#include <linux/compiler_attributes.h>
>> #include <linux/list.h>
>> #include <linux/module.h>
>> #include <linux/wmi.h>
>> @@ -15,6 +15,24 @@
>>
>> #define DELL_WMI_DESCRIPTOR_GUID "8D9DDCBC-A997-11DA-B012-B622A1EF5492"
>>
>> +/*
>> + * Descriptor buffer is 128 byte long and contains:
>> + *
>> + * Name Offset Length Value
>> + * Vendor Signature 0 4 "DELL"
>> + * Object Signature 4 4 " WMI"
>> + * WMI Interface Version 8 4 <version>
>> + * WMI buffer length 12 4 <length>
>> + * WMI hotfix number 16 4 <hotfix>
>> + */
>> +struct descriptor {
>> + char vendor_signature[4];
>> + char object_signature[4];
>> + __le32 interface_version;
>> + __le32 buffer_length;
>> + __le32 hotfix_number;
>> +} __packed;
>> +
>> struct descriptor_priv {
>> struct list_head list;
>> u32 interface_version;
>> @@ -88,76 +106,58 @@ bool dell_wmi_get_hotfix(u32 *hotfix)
>> }
>> EXPORT_SYMBOL_GPL(dell_wmi_get_hotfix);
>>
>> -/*
>> - * Descriptor buffer is 128 byte long and contains:
>> - *
>> - * Name Offset Length Value
>> - * Vendor Signature 0 4 "DELL"
>> - * Object Signature 4 4 " WMI"
>> - * WMI Interface Version 8 4 <version>
>> - * WMI buffer length 12 4 <length>
>> - * WMI hotfix number 16 4 <hotfix>
>> - */
>> -static int dell_wmi_descriptor_probe(struct wmi_device *wdev,
>> - const void *context)
>> +static int dell_wmi_descriptor_probe(struct wmi_device *wdev, const void *context)
>> {
>> - union acpi_object *obj = NULL;
>> struct descriptor_priv *priv;
>> - u32 *buffer;
>> + struct wmi_buffer buffer;
>> + struct descriptor *desc;
>> int ret;
>>
>> - obj = wmidev_block_query(wdev, 0);
>> - if (!obj) {
>> - dev_err(&wdev->dev, "failed to read Dell WMI descriptor\n");
>> - ret = -EIO;
>> - goto out;
>> - }
>> + ret = wmidev_query_block(wdev, 0, &buffer);
>> + if (ret < 0)
>> + return ret;
>>
>> - if (obj->type != ACPI_TYPE_BUFFER) {
>> - dev_err(&wdev->dev, "Dell descriptor has wrong type\n");
>> + if (buffer.length < sizeof(*desc)) {
> Hi again,
>
> Thinking some more of this...
>
> Since many of these drivers will need to do this size check and assign
> into some variable that is different from the one passed to
> wmidev_query_block(), would it make sense to move those into generic code?
> It probably requires a macro so you'd have access to type information.

You mean something like wmidev_block_query_sized(wdev, instance, size)?

Personally i see little benefit in having the assignment handled by a macro.

Thanks,
Armin Wolf