Message-ID: <f163ef7e-41ee-cfa4-67c5-4325d1381110@redhat.com>
Date:   Mon, 30 Jan 2023 16:09:52 +0100
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Subject: Re: [PATCH 4/5] platform/x86: dell-ddv: Add "force" module param
Content-Language: en-US
To:     Armin Wolf <W_Armin@gmx.de>, markgross@kernel.org
Cc:     jdelvare@suse.com, linux@roeck-us.net,
        platform-driver-x86@vger.kernel.org, linux-hwmon@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20230126194021.381092-1-W_Armin@gmx.de>
 <20230126194021.381092-5-W_Armin@gmx.de>
From:   Hans de Goede <hdegoede@redhat.com>
In-Reply-To: <20230126194021.381092-5-W_Armin@gmx.de>
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Precedence: bulk

Hi again,

On 1/26/23 20:40, Armin Wolf wrote:
> Until now, the dell-wmi-ddv driver needs to be manually
> patched and compiled to test compatibility with unknown
> DDV WMI interface versions.
> Add a module param to allow users to force loading even
> when a unknown interface version was detected. Since this
> might cause various unwanted side effects, the module param
> is marked as unsafe.
> Also update kernel-parameters.txt.
> 
> Signed-off-by: Armin Wolf <W_Armin@gmx.de>
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  3 +++
>  drivers/platform/x86/dell/dell-wmi-ddv.c        | 13 +++++++++++--
>  2 files changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
> index 6cfa6e3996cf..9bbff5113427 100644
> --- a/Documentation/admin-guide/kernel-parameters.txt
> +++ b/Documentation/admin-guide/kernel-parameters.txt
> @@ -1024,6 +1024,9 @@
>  	dell_smm_hwmon.fan_max=
>  			[HW] Maximum configurable fan speed.
> 
> +	dell_wmi_ddv.force=
> +			[HW] Do not check for supported WMI interface versions.
> +
>  	dfltcc=		[HW,S390]
>  			Format: { on | off | def_only | inf_only | always }
>  			on:       s390 zlib hardware support for compression on

In my previous email I forgot to add that I have dropped this bit. I appreciate
the effort to document this parameter, but if we add documentation for all
existing parameters to Documentation/admin-guide/kernel-parameters.txt then
the file will become quite unyielding / unusable.

So in general we only add new parameters which we expect to be important for
a large group of users or necessary to debug serious problems like machines
not booting.

I realize that a bunch of parameters in there do not match this, like
e.g. dell_smm_hwmon.fan_max, these are just from older times when
there were just less parameters, so listing them all was still ok.

So I have merged this patch, but with the Documentation/admin-guide/kernel-parameters.txt
bit dropped.

Regards,

Hans


> diff --git a/drivers/platform/x86/dell/dell-wmi-ddv.c b/drivers/platform/x86/dell/dell-wmi-ddv.c
> index 58fadb74e86a..9695bf493ea6 100644
> --- a/drivers/platform/x86/dell/dell-wmi-ddv.c
> +++ b/drivers/platform/x86/dell/dell-wmi-ddv.c
> @@ -34,6 +34,10 @@
>  #define DELL_EPPID_LENGTH	20
>  #define DELL_EPPID_EXT_LENGTH	23
> 
> +static bool force;
> +module_param_unsafe(force, bool, 0);
> +MODULE_PARM_DESC(force, "Force loading without checking for supported WMI interface versions");
> +
>  enum dell_ddv_method {
>  	DELL_DDV_BATTERY_DESIGN_CAPACITY	= 0x01,
>  	DELL_DDV_BATTERY_FULL_CHARGE_CAPACITY	= 0x02,
> @@ -349,8 +353,13 @@ static int dell_wmi_ddv_probe(struct wmi_device *wdev, const void *context)
>  		return ret;
> 
>  	dev_dbg(&wdev->dev, "WMI interface version: %d\n", version);
> -	if (version < DELL_DDV_SUPPORTED_VERSION_MIN || version > DELL_DDV_SUPPORTED_VERSION_MAX)
> -		return -ENODEV;
> +	if (version < DELL_DDV_SUPPORTED_VERSION_MIN || version > DELL_DDV_SUPPORTED_VERSION_MAX) {
> +		if (!force)
> +			return -ENODEV;
> +
> +		dev_warn(&wdev->dev, "Loading despite unsupported WMI interface version (%u)\n",
> +			 version);
> +	}
> 
>  	data = devm_kzalloc(&wdev->dev, sizeof(*data), GFP_KERNEL);
>  	if (!data)
> --
> 2.30.2
>