linux-kernel - Re: [PATCH] acpi/battery: fix wrong value of capacity_now reported by few battery types when fully charged (resend)

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Date:	Tue, 17 Jun 2014 22:07:32 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Josef Gajdusek <atx@....name>
Cc:	lenb@...nel.org, linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] acpi/battery: fix wrong value of capacity_now reported by few battery types when fully charged (resend)

On Tuesday, June 17, 2014 06:41:54 PM Josef Gajdusek wrote:
> It seems that some batteries (noticed on DELL JYPJ136) assume 
> capacity_now = design_capacity when fully charged. This causes 
> reported capacity to suddenly jump to >full_charge_capacity (and that 
> means capacity reported to userspace is >100% and incorrect) 
> values after 99%. This patch attempts to detect this bug, notifies 
> userspace and trims the value to full_charge_capacity.
> 
> Signed-off-by: Josef Gajdusek <atx@....name>
> ---
> Relaxed the check as you suggested and added printk_once.
> 
> > Why don't you use the
> >
> >    battery->capacity_now > battery->full_charge_capacity
> >
> > check here?  That would be more robust, wouldn't it?
> 
> To allow userspace to see that there is some unknown bug we do not know yet 
> with the battery. This is taken care of much more elegantly by the printk 
> now.
> 
> diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
> index e48fc98..57a800c 100644
> --- a/drivers/acpi/battery.c
> +++ b/drivers/acpi/battery.c
> @@ -532,6 +532,18 @@ static int acpi_battery_get_state(struct acpi_battery *battery)
>  			" invalid.\n");
>  	}
>  
> +	/* When fully charged, some batteries wrongly report
> +	 * capacity_now = design_capacity instead of = full_charge_capacity
> +	 */
> +	if (battery->capacity_now > battery->full_charge_capacity) {

But it still is necessary to check if battery->full_charge_capacity is
not ACPI_BATTERY_VALUE_UNKNOWN, isn't it?

> +		battery->capacity_now = battery->full_charge_capacity;
> +		printk_once(KERN_WARNING FW_BUG
> +			"battery: reported current charge level (%d) "
> +			"is higher than reported maximum charge level (%d)."
> +			"This is normal on some systems.\n",
> +			battery->capacity_now, battery->full_charge_capacity);
> +	}
> +
>  	if (test_bit(ACPI_BATTERY_QUIRK_PERCENTAGE_CAPACITY, &battery->flags)
>  	    && battery->capacity_now >= 0 && battery->capacity_now <= 100)
>  		battery->capacity_now = (battery->capacity_now *

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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