Re: [PATCH v2 02/19] ACPI: LPIT: move to use bus_get_dev_root()

[Rafael J. Wysocki]

On Wed, Mar 22, 2023 at 9:36 AM Greg Kroah-Hartman
<gregkh@xxxxxxxxxxxxxxxxxxx> wrote:
>
> Direct access to the struct bus_type dev_root pointer is going away soon
> so replace that with a call to bus_get_dev_root() instead, which is what
> it is there for.
>
> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> Cc: Len Brown <lenb@xxxxxxxxxx>
> Cc: linux-acpi@xxxxxxxxxxxxxxx
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>

> ---
> v2: - change logic to test for dev_root at the beginning of the function
>       and error out then based on review comments from Rafael.
>     - fix error handling for ioremap() call to properly drop the
>       reference on dev_root if it failed.
>
>  drivers/acpi/acpi_lpit.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/acpi/acpi_lpit.c b/drivers/acpi/acpi_lpit.c
> index 3843d2576d3f..c5598b6d5db8 100644
> --- a/drivers/acpi/acpi_lpit.c
> +++ b/drivers/acpi/acpi_lpit.c
> @@ -98,6 +98,12 @@ EXPORT_SYMBOL_GPL(lpit_read_residency_count_address);
>  static void lpit_update_residency(struct lpit_residency_info *info,
>                                  struct acpi_lpit_native *lpit_native)
>  {
> +       struct device *dev_root = bus_get_dev_root(&cpu_subsys);
> +
> +       /* Silently fail, if cpuidle attribute group is not present */
> +       if (!dev_root)
> +               return;
> +
>         info->frequency = lpit_native->counter_frequency ?
>                                 lpit_native->counter_frequency : tsc_khz * 1000;
>         if (!info->frequency)
> @@ -108,18 +114,18 @@ static void lpit_update_residency(struct lpit_residency_info *info,
>                 info->iomem_addr = ioremap(info->gaddr.address,
>                                                    info->gaddr.bit_width / 8);
>                 if (!info->iomem_addr)
> -                       return;
> +                       goto exit;
>
> -               /* Silently fail, if cpuidle attribute group is not present */
> -               sysfs_add_file_to_group(&cpu_subsys.dev_root->kobj,
> +               sysfs_add_file_to_group(&dev_root->kobj,
>                                         &dev_attr_low_power_idle_system_residency_us.attr,
>                                         "cpuidle");
>         } else if (info->gaddr.space_id == ACPI_ADR_SPACE_FIXED_HARDWARE) {
> -               /* Silently fail, if cpuidle attribute group is not present */
> -               sysfs_add_file_to_group(&cpu_subsys.dev_root->kobj,
> +               sysfs_add_file_to_group(&dev_root->kobj,
>                                         &dev_attr_low_power_idle_cpu_residency_us.attr,
>                                         "cpuidle");
>         }
> +exit:
> +       put_device(dev_root);
>  }
>
>  static void lpit_process(u64 begin, u64 end)
> --
> 2.40.0
>