Re: [PATCH v5 6/9] hwmon: (dell-smm) Use new buffer-based WMI API
From: Ilpo Järvinen
Date: Tue Jun 09 2026 - 07:40:39 EST
On Fri, 5 Jun 2026, Armin Wolf wrote:
> Use the new buffer-based WMI API to also support ACPI firmware
> implementations that do not use ACPI buffers for returning the
> results of a SMM call.
>
> Acked-by: Guenter Roeck <linux@xxxxxxxxxxxx>
> Signed-off-by: Armin Wolf <W_Armin@xxxxxx>
> ---
> drivers/hwmon/dell-smm-hwmon.c | 47 ++++++++++++----------------------
> 1 file changed, 16 insertions(+), 31 deletions(-)
>
> diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
> index 038edffc1ac7..0dbee562220b 100644
> --- a/drivers/hwmon/dell-smm-hwmon.c
> +++ b/drivers/hwmon/dell-smm-hwmon.c
> @@ -12,8 +12,9 @@
>
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> -#include <linux/acpi.h>
> +#include <linux/align.h>
> #include <linux/capability.h>
> +#include <linux/compiler_attributes.h>
> #include <linux/cpu.h>
> #include <linux/ctype.h>
> #include <linux/delay.h>
> @@ -36,10 +37,10 @@
> #include <linux/thermal.h>
> #include <linux/types.h>
> #include <linux/uaccess.h>
> +#include <linux/unaligned.h>
> #include <linux/wmi.h>
>
> #include <linux/i8k.h>
> -#include <linux/unaligned.h>
>
> #define I8K_SMM_FN_STATUS 0x0025
> #define I8K_SMM_POWER_STATUS 0x0069
> @@ -232,7 +233,7 @@ static const struct dell_smm_ops i8k_smm_ops = {
> /*
> * Call the System Management Mode BIOS over WMI.
> */
> -static ssize_t wmi_parse_register(u8 *buffer, u32 length, unsigned int *reg)
> +static ssize_t wmi_parse_register(u8 *buffer, size_t length, unsigned int *reg)
> {
> __le32 value;
> u32 reg_size;
> @@ -253,7 +254,7 @@ static ssize_t wmi_parse_register(u8 *buffer, u32 length, unsigned int *reg)
> return reg_size + sizeof(reg_size);
> }
>
> -static int wmi_parse_response(u8 *buffer, u32 length, struct smm_regs *regs)
> +static int wmi_parse_response(u8 *buffer, size_t length, struct smm_regs *regs)
> {
> unsigned int *registers[] = {
> ®s->eax,
> @@ -261,7 +262,7 @@ static int wmi_parse_response(u8 *buffer, u32 length, struct smm_regs *regs)
> ®s->ecx,
> ®s->edx
> };
> - u32 offset = 0;
> + size_t offset = 0;
> ssize_t ret;
> int i;
>
> @@ -273,19 +274,16 @@ static int wmi_parse_response(u8 *buffer, u32 length, struct smm_regs *regs)
> if (ret < 0)
> return ret;
>
> - offset += ret;
> + /* WMI aligns u32 integers on a 4 byte boundary */
> + offset = ALIGN(offset + ret, 4);
> }
>
> - if (offset != length)
> - return -ENOMSG;
> -
> return 0;
> }
>
> static int wmi_smm_call(struct device *dev, struct smm_regs *regs)
> {
> struct wmi_device *wdev = container_of(dev, struct wmi_device, dev);
> - struct acpi_buffer out = { ACPI_ALLOCATE_BUFFER, NULL };
> u32 wmi_payload[] = {
> sizeof(regs->eax),
> regs->eax,
> @@ -296,32 +294,19 @@ static int wmi_smm_call(struct device *dev, struct smm_regs *regs)
> sizeof(regs->edx),
> regs->edx
> };
> - const struct acpi_buffer in = {
> + const struct wmi_buffer in = {
> .length = sizeof(wmi_payload),
> - .pointer = &wmi_payload,
> + .data = &wmi_payload,
> };
> - union acpi_object *obj;
> - acpi_status status;
> + struct wmi_buffer out;
> int ret;
>
> - status = wmidev_evaluate_method(wdev, 0x0, DELL_SMM_LEGACY_EXECUTE, &in, &out);
> - if (ACPI_FAILURE(status))
> - return -EIO;
> -
> - obj = out.pointer;
> - if (!obj)
> - return -ENODATA;
> -
> - if (obj->type != ACPI_TYPE_BUFFER) {
> - ret = -ENOMSG;
> -
> - goto err_free;
> - }
> -
> - ret = wmi_parse_response(obj->buffer.pointer, obj->buffer.length, regs);
> + ret = wmidev_invoke_method(wdev, 0x0, DELL_SMM_LEGACY_EXECUTE, &in, &out, sizeof(__le32));
> + if (ret < 0)
> + return ret;
>
> -err_free:
> - kfree(obj);
> + ret = wmi_parse_response(out.data, out.length, regs);
> + kfree(out.data);
>
> return ret;
If you used __free() here, you could do just:
return wmi_parse_response(out.data, out.length, regs);
> }
>
--
i.