Re: [PATCH 1/9] cpuidle: psci: Transition to the faux device interface

[Rafael J. Wysocki]

On Mon, Mar 17, 2025 at 11:13 AM Sudeep Holla <sudeep.holla@xxxxxxx> wrote:
>
> The PSCI cpuidle driver does not require the creation of a platform
> device. Originally, this approach was chosen for simplicity when the
> driver was first implemented.
>
> With the introduction of the lightweight faux device interface, we now
> have a more appropriate alternative. Migrate the driver to utilize the
> faux bus, given that the platform device it previously created was not
> a real one anyway. This will simplify the code, reducing its footprint
> while maintaining functionality.
>
> Cc: Lorenzo Pieralisi <lpieralisi@xxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rafael@xxxxxxxxxx>
> Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
> Cc: linux-pm@xxxxxxxxxxxxxxx
> Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>

Do you want me to pick up this one?

> ---
>  drivers/cpuidle/cpuidle-psci.c | 26 +++++++++-----------------
>  1 file changed, 9 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/cpuidle/cpuidle-psci.c b/drivers/cpuidle/cpuidle-psci.c
> index 2562dc001fc1de69732ef28f383d2809262a3d96..3e38f712dab3785d5caa8d103fd0146156005921 100644
> --- a/drivers/cpuidle/cpuidle-psci.c
> +++ b/drivers/cpuidle/cpuidle-psci.c
> @@ -16,7 +16,7 @@
>  #include <linux/kernel.h>
>  #include <linux/module.h>
>  #include <linux/of.h>
> -#include <linux/platform_device.h>
> +#include <linux/device/faux.h>
>  #include <linux/psci.h>
>  #include <linux/pm_domain.h>
>  #include <linux/pm_runtime.h>
> @@ -404,14 +404,14 @@ static int psci_idle_init_cpu(struct device *dev, int cpu)
>   * to register cpuidle driver then rollback to cancel all CPUs
>   * registration.
>   */
> -static int psci_cpuidle_probe(struct platform_device *pdev)
> +static int psci_cpuidle_probe(struct faux_device *fdev)
>  {
>         int cpu, ret;
>         struct cpuidle_driver *drv;
>         struct cpuidle_device *dev;
>
>         for_each_possible_cpu(cpu) {
> -               ret = psci_idle_init_cpu(&pdev->dev, cpu);
> +               ret = psci_idle_init_cpu(&fdev->dev, cpu);
>                 if (ret)
>                         goto out_fail;
>         }
> @@ -431,26 +431,18 @@ static int psci_cpuidle_probe(struct platform_device *pdev)
>         return ret;
>  }
>
> -static struct platform_driver psci_cpuidle_driver = {
> +static struct faux_device_ops psci_cpuidle_ops = {
>         .probe = psci_cpuidle_probe,
> -       .driver = {
> -               .name = "psci-cpuidle",
> -       },
>  };
>
>  static int __init psci_idle_init(void)
>  {
> -       struct platform_device *pdev;
> -       int ret;
> +       struct faux_device *fdev;
>
> -       ret = platform_driver_register(&psci_cpuidle_driver);
> -       if (ret)
> -               return ret;
> -
> -       pdev = platform_device_register_simple("psci-cpuidle", -1, NULL, 0);
> -       if (IS_ERR(pdev)) {
> -               platform_driver_unregister(&psci_cpuidle_driver);
> -               return PTR_ERR(pdev);
> +       fdev = faux_device_create("psci-cpuidle", NULL, &psci_cpuidle_ops);
> +       if (!fdev) {
> +               pr_err("Failed to create psci-cpuidle device\n");
> +               return -ENODEV;
>         }
>
>         return 0;
>
> --
> 2.34.1
>