linux-kernel - Re: [PATCH] platform/x86: dell-wmi-sysman: work around for BIOS bug

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Message-ID: <06db27af-7387-9343-acd3-d75e8c46b623@redhat.com>
Date:   Wed, 2 Dec 2020 13:21:11 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Divya Bharathi <divya27392@...il.com>, dvhart@...radead.org
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        platform-driver-x86@...r.kernel.org,
        Divya Bharathi <divya.bharathi@...l.com>,
        Mario Limonciello <mario.limonciello@...l.com>,
        Prasanth KSR <prasanth.ksr@...l.com>
Subject: Re: [PATCH] platform/x86: dell-wmi-sysman: work around for BIOS bug

Hi,

On 12/2/20 7:56 AM, Divya Bharathi wrote:
> BIOS sets incorrect value (zero) when SET value passed for integer attribute
> with + sign. Added workaround to remove + sign before passing input to BIOS
> 
> Co-developed-by: Mario Limonciello <mario.limonciello@...l.com>
> Signed-off-by: Mario Limonciello <mario.limonciello@...l.com>
> Co-developed-by: Prasanth KSR <prasanth.ksr@...l.com>
> Signed-off-by: Prasanth KSR <prasanth.ksr@...l.com>
> Signed-off-by: Divya Bharathi <divya.bharathi@...l.com>
> ---
>  drivers/platform/x86/dell-wmi-sysman/int-attributes.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/platform/x86/dell-wmi-sysman/int-attributes.c b/drivers/platform/x86/dell-wmi-sysman/int-attributes.c
> index ea773d8e8d3a..f30d155135c3 100644
> --- a/drivers/platform/x86/dell-wmi-sysman/int-attributes.c
> +++ b/drivers/platform/x86/dell-wmi-sysman/int-attributes.c
> @@ -39,7 +39,7 @@ static ssize_t current_value_show(struct kobject *kobj, struct kobj_attribute *a
>   * @instance_id: The instance on which input is validated
>   * @buf: Input value
>   */
> -static int validate_integer_input(int instance_id, const char *buf)
> +static int validate_integer_input(int instance_id, char *buf)
>  {
>  	int in_val;
>  	int ret;
> @@ -51,6 +51,12 @@ static int validate_integer_input(int instance_id, const char *buf)
>  			in_val > wmi_priv.integer_data[instance_id].max_value)
>  		return -EINVAL;
>  
> +	/* workaround for BIOS error.
> +	 * validate input to avoid setting 0 when integer input passed with + sign
> +	 */
> +	if (*buf == '+')
> +		memmove(buf, (buf + 1), strlen(buf));

Can you please use "strlen(buf + 1) + 1" as last argument to the memmove?

I know the effect is the same but that makes it much clearer that you
are also moving the terminating 0 (which at first I thought you were not).

Otherwise this looks good to me.

Regards,

Hans