Commit c7891884 authored by Armin Wolf's avatar Armin Wolf Committed by Hans de Goede
Browse files

platform/x86: dell-ddv: Warn if ePPID has a suspicious length 



On some systems (like the Dell Inspiron 3505), the acpi operation
region holding the ePPID string is two bytes too short, causing
acpi functions like ToString() to omit the last two bytes.
This does not happen on Windows, supposedly due to their implementation
of ToString() ignoring buffer boundaries.
Inform users if the ePPID length differs from the Dell specification
so they can complain to Dell to fix their BIOS.

Tested on a Dell Inspiron 3505.

Signed-off-by: default avatarArmin Wolf <W_Armin@gmx.de>
Link: https://lore.kernel.org/r/20221102212336.380257-2-W_Armin@gmx.de


Reviewed-by: default avatarHans de Goede <hdegoede@redhat.com>
Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
parent 84fa20c2

drivers/platform/x86/dell/dell-wmi-ddv.c

+9 −0
Original line number Diff line number Diff line
@@ -10,12 +10,14 @@ 
#include <linux/acpi.h>

#include <linux/debugfs.h>

#include <linux/device.h>

#include <linux/dev_printk.h>

#include <linux/kernel.h>

#include <linux/kstrtox.h>

#include <linux/math.h>

#include <linux/module.h>

#include <linux/limits.h>

#include <linux/power_supply.h>

#include <linux/printk.h>

#include <linux/seq_file.h>

#include <linux/sysfs.h>

#include <linux/wmi.h>
@@ -27,6 +29,9 @@ 
#define DELL_DDV_SUPPORTED_INTERFACE 2

#define DELL_DDV_GUID	"8A42EA14-4F2A-FD45-6422-0087F7A7E608"



#define DELL_EPPID_LENGTH	20

#define DELL_EPPID_EXT_LENGTH	23



enum dell_ddv_method {

	DELL_DDV_BATTERY_DESIGN_CAPACITY	= 0x01,

	DELL_DDV_BATTERY_FULL_CHARGE_CAPACITY	= 0x02,
@@ -196,6 +201,10 @@ static ssize_t eppid_show(struct device *dev, struct device_attribute *attr, cha 
	if (ret < 0)

		return ret;



	if (obj->string.length != DELL_EPPID_LENGTH && obj->string.length != DELL_EPPID_EXT_LENGTH)

		dev_info_once(&data->wdev->dev, FW_INFO "Suspicious ePPID length (%d)\n",

			      obj->string.length);



	ret = sysfs_emit(buf, "%s\n", obj->string.pointer);



	kfree(obj);