linux-kernel - Re: [PATCH v3 1/3] platform/x86: dell-privacy: Add support for Dell hardware privacy

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Message-ID: <31982e8d-3b0d-7187-8798-900f95d876ee@linux.intel.com>
Date:   Tue, 16 Feb 2021 08:56:52 -0600
From:   Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>
To:     Perry Yuan <perry979106@...il.com>,
        Perry Yuan <Perry.Yuan@...l.com>, oder_chiou@...ltek.com,
        perex@...ex.cz, tiwai@...e.com, hdegoede@...hat.com,
        mgross@...ux.intel.com
Cc:     alsa-devel@...a-project.org, Mario.Limonciello@...l.com,
        linux-kernel@...r.kernel.org, lgirdwood@...il.com,
        platform-driver-x86@...r.kernel.org, broonie@...nel.org
Subject: Re: [PATCH v3 1/3] platform/x86: dell-privacy: Add support for Dell
 hardware privacy


>>> +static const struct acpi_device_id privacy_acpi_device_ids[] = {
>>> +    {"PNP0C09", 0},
>>> +    { },
>>> +};
>>> +MODULE_DEVICE_TABLE(acpi, privacy_acpi_device_ids);
>>> +
>>> +static struct platform_driver dell_privacy_platform_drv = {
>>> +    .driver = {
>>> +        .name = PRIVACY_PLATFORM_NAME,
>>> +        .acpi_match_table = ACPI_PTR(privacy_acpi_device_ids),
>>> +    },
>>
>> no .probe?
> Originally i added the probe here, but it cause the driver  .probe 
> called twice. after i use platform_driver_probe to register the driver 
> loading process, the duplicated probe issue resolved.
> 
> I
>>
>>> +    .remove = dell_privacy_acpi_remove,
>>> +};
>>> +
>>> +int __init dell_privacy_acpi_init(void)
>>> +{
>>> +    int err;
>>> +    struct platform_device *pdev;
>>> +    int privacy_capable = wmi_has_guid(DELL_PRIVACY_GUID);
>>> +
>>> +    if (!wmi_has_guid(DELL_PRIVACY_GUID))
>>> +        return -ENODEV;
>>> +
>>> +    privacy_acpi = kzalloc(sizeof(*privacy_acpi), GFP_KERNEL);
>>> +    if (!privacy_acpi)
>>> +        return -ENOMEM;
>>> +
>>> +    pdev = platform_device_register_simple(
>>> +            PRIVACY_PLATFORM_NAME, PLATFORM_DEVID_NONE, NULL, 0);
>>> +    if (IS_ERR(pdev)) {
>>> +        err = PTR_ERR(pdev);
>>> +        goto pdev_err;
>>> +    }
>>> +    err = platform_driver_probe(&dell_privacy_platform_drv,
>>> +            dell_privacy_acpi_probe);
>>> +    if (err)
>>> +        goto pdrv_err;
>>
>> why is the probe done here? Put differently, what prevents you from 
>> using a 'normal' platform driver, and do the leds_setup in the .probe()?
> At first ,I used the normal platform driver framework, however tt cause 
> the driver  .probe called twice. after i use platform_driver_probe to 
> register the driver loading process, the duplicated probe issue resolved.

This sounds very odd...

this looks like a conflict with the ACPI subsystem finding a device and 
probing the driver that's associated with the PNP0C09 HID, and then this 
module __init  creating a device manually which leads to a second probe

Neither the platform_device_register_simple() nor 
platform_driver_probe() seem necessary?