linux-kernel - Re: [PATCH v5 1/3] platform/x86: intel_pmc_core: Convert to a platform

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Date:   Thu, 11 Apr 2019 16:44:40 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Rajat Jain <rajatja@...gle.com>
Cc:     Rajneesh Bhardwaj <rajneesh.bhardwaj@...el.com>,
        Vishwanath Somayaji <vishwanath.somayaji@...el.com>,
        Darren Hart <dvhart@...radead.org>,
        Andy Shevchenko <andy@...radead.org>,
        Platform Driver <platform-driver-x86@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Rafael J Wysocki <rafael.j.wysocki@...el.com>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        Furquan Shaikh <furquan@...gle.com>,
        Evan Green <evgreen@...gle.com>,
        Rajat Jain <rajatxjain@...il.com>
Subject: Re: [PATCH v5 1/3] platform/x86: intel_pmc_core: Convert to a platform_driver

On Thu, Apr 11, 2019 at 3:37 AM Rajat Jain <rajatja@...gle.com> wrote:
>
> Convert the intel_pmc_core driver to a platform driver, and attach using
> the ACPI enumeration method (via the ACPI device "INT33A1").

>         cpu_id = x86_match_cpu(intel_pmc_core_ids);
>         if (!cpu_id)
>                 return -ENODEV;
> @@ -888,28 +893,49 @@ static int __init pmc_core_probe(void)
>         mutex_init(&pmcdev->lock);
>         pmcdev->pmc_xram_read_bit = pmc_core_check_read_lock_bit();
>
> +       dmi_check_system(pmc_core_dmi_table);
> +       platform_set_drvdata(pdev, pmcdev);
> +
>         err = pmc_core_dbgfs_register(pmcdev);
>         if (err < 0) {
> -               pr_warn(" debugfs register failed.\n");
> +               dev_warn(&pdev->dev, "debugfs register failed.\n");
>                 iounmap(pmcdev->regbase);
>                 return err;
>         }
>
> -       dmi_check_system(pmc_core_dmi_table);
> -       pr_info(" initialized\n");

> +       dev_info(&pdev->dev, " initialized\n");
> +       device_initialized = true;

First you do something, then print it's done, and not other way around.

> +
>         return 0;
>  }
> -module_init(pmc_core_probe)
>
> -static void __exit pmc_core_remove(void)
> +static int pmc_core_remove(struct platform_device *pdev)
>  {
> -       struct pmc_dev *pmcdev = &pmc;
> +       struct pmc_dev *pmcdev = platform_get_drvdata(pdev);
>
> +       platform_set_drvdata(pdev, NULL);
>         pmc_core_dbgfs_unregister(pmcdev);
>         mutex_destroy(&pmcdev->lock);
>         iounmap(pmcdev->regbase);
> +       return 0;
>  }
> -module_exit(pmc_core_remove)
> +
> +static const struct acpi_device_id pmc_core_acpi_ids[] = {
> +       {"INT33A1", 0}, /* _HID for Intel Power Engine, _CID PNP0D80*/
> +       { }
> +};
> +MODULE_DEVICE_TABLE(acpi, pmc_core_acpi_ids);
> +
> +static struct platform_driver pmc_core_driver = {
> +       .driver = {
> +               .name = "pmc_core",
> +               .acpi_match_table = ACPI_PTR(pmc_core_acpi_ids),
> +       },
> +       .probe = pmc_core_probe,
> +       .remove = pmc_core_remove,
> +};
> +
> +module_platform_driver(pmc_core_driver);

So, this patch has a bisectability issue. After it AFAIU some
platforms will not be able to enumerate the device.

To avoid such you have to reconsider logic behind this conversion, i.e.
1. Split the driver to core part and current initialization mechanism
2. Add platform driver as a separate module.

-- 
With Best Regards,
Andy Shevchenko