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

[Armin Wolf <W_Armin@gmx.de>]

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