linux-kernel - Re: [PATCH] ACPI: DPTF: Fix reading of attributes

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Date:   Wed, 28 Jul 2021 18:42:39 +0200
From:   "Rafael J. Wysocki" <rafael@...nel.org>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI: DPTF: Fix reading of attributes

On Tue, Jul 27, 2021 at 6:18 PM Srinivas Pandruvada
<srinivas.pandruvada@...ux.intel.com> wrote:
>
> The current assumption that methods to read PCH FIVR attributes will
> return integer, is not correct. There is no good way to return integer
> as negative numbers are also valid.
>
> These read methods return a package of integers. The first integer returns
> status, which is 0 on success and any other value for failure. When the
> returned status is zero, then the second integer returns the actual value.
>
> This change fixes this issue by replacing acpi_evaluate_integer() with
> acpi_evaluate_object() and use acpi_extract_package() to extract results.
>
> Fixes: 2ce6324eadb01 ("ACPI: DPTF: Add PCH FIVR participant driver")
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
> Cc: stable@...r.kernel.org # 5.10+

Applied as 5.14-rc material.

I'll apply the [2/2[ when this one is merged.

> ---
>  drivers/acpi/dptf/dptf_pch_fivr.c | 51 ++++++++++++++++++++++++++-----
>  1 file changed, 43 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/acpi/dptf/dptf_pch_fivr.c b/drivers/acpi/dptf/dptf_pch_fivr.c
> index 5fca18296bf6..550b9081fcbc 100644
> --- a/drivers/acpi/dptf/dptf_pch_fivr.c
> +++ b/drivers/acpi/dptf/dptf_pch_fivr.c
> @@ -9,6 +9,42 @@
>  #include <linux/module.h>
>  #include <linux/platform_device.h>
>
> +struct pch_fivr_resp {
> +       u64 status;
> +       u64 result;
> +};
> +
> +static int pch_fivr_read(acpi_handle handle, char *method, struct pch_fivr_resp *fivr_resp)
> +{
> +       struct acpi_buffer resp = { sizeof(struct pch_fivr_resp), fivr_resp};
> +       struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
> +       struct acpi_buffer format = { sizeof("NN"), "NN" };
> +       union acpi_object *obj;
> +       acpi_status status;
> +       int ret = -EFAULT;
> +
> +       status = acpi_evaluate_object(handle, method, NULL, &buffer);
> +       if (ACPI_FAILURE(status))
> +               return ret;
> +
> +       obj = buffer.pointer;
> +       if (!obj || obj->type != ACPI_TYPE_PACKAGE)
> +               goto release_buffer;
> +
> +       status = acpi_extract_package(obj, &format, &resp);
> +       if (ACPI_FAILURE(status))
> +               goto release_buffer;
> +
> +       if (fivr_resp->status)
> +               goto release_buffer;
> +
> +       ret = 0;
> +
> +release_buffer:
> +       kfree(buffer.pointer);
> +       return ret;
> +}
> +
>  /*
>   * Presentation of attributes which are defined for INT1045
>   * They are:
> @@ -23,15 +59,14 @@ static ssize_t name##_show(struct device *dev,\
>                            char *buf)\
>  {\
>         struct acpi_device *acpi_dev = dev_get_drvdata(dev);\
> -       unsigned long long val;\
> -       acpi_status status;\
> +       struct pch_fivr_resp fivr_resp;\
> +       int status;\
>  \
> -       status = acpi_evaluate_integer(acpi_dev->handle, #method,\
> -                                      NULL, &val);\
> -       if (ACPI_SUCCESS(status))\
> -               return sprintf(buf, "%d\n", (int)val);\
> -       else\
> -               return -EINVAL;\
> +       status = pch_fivr_read(acpi_dev->handle, #method, &fivr_resp);\
> +       if (status)\
> +               return status;\
> +\
> +       return sprintf(buf, "%llu\n", fivr_resp.result);\
>  }
>
>  #define PCH_FIVR_STORE(name, method) \
> --
> 2.31.1
>