Commit f3f837e5 authored by Bill Richardson's avatar Bill Richardson Committed by Olof Johansson

platform/chrome: Expose Chrome OS Lightbar to users

This adds some sysfs entries to provide userspace control of the
four-element LED "lightbar" on the Chromebook Pixel. This only instantiates
the lightbar controls if the device actually exists.

To prevent DoS attacks, this interface is limited to 20 accesses/second,
although that rate can be adjusted by a privileged user.

On Chromebooks without a lightbar, this should have no effect. On the
Chromebook Pixel, you should be able to do things like this:

    $ cd /sys/devices/virtual/chromeos/cros_ec/lightbar
    $ echo 0x80 > brightness
    $ echo 255 > brightness
    $
    $ cat sequence
    S0
    $ echo konami > sequence
    $ cat sequence
    KONAMI
    $
    $ cat sequence
    S0

And

    $ cd /sys/devices/virtual/chromeos/cros_ec/lightbar
    $ echo stop > sequence
    $ echo "4 255 255 255" > led_rgb
    $ echo "0 255 0 0  1 0 255 0  2 0 0 255  3 255 255 0" > led_rgb
    $ echo run  > sequence

Test the DoS prevention with this:

    $ cd /sys/devices/virtual/chromeos/cros_ec/lightbar
    $ echo 500 > interval_msec
    $ time (cat version version version version version version version)
Signed-off-by: default avatarBill Richardson <wfrichar@chromium.org>
Reviewed-by: default avatarOlof Johansson <olofj@chromium.org>
Tested-by: default avatarDoug Anderson <dianders@chromium.org>
Reviewed-by: default avatarBenson Leung <bleung@chromium.org>
Signed-off-by: default avatarJavier Martinez Canillas <javier.martinez@collabora.co.uk>
Tested-by: default avatarGwendal Grignou <gwendal@chromium.org>
Reviewed-by: default avatarGwendal Grignou <gwendal@chromium.org>
Signed-off-by: default avatarOlof Johansson <olof@lixom.net>
parent 71af4b52
obj-$(CONFIG_CHROMEOS_LAPTOP) += chromeos_laptop.o
obj-$(CONFIG_CHROMEOS_PSTORE) += chromeos_pstore.o
cros_ec_devs-objs := cros_ec_dev.o cros_ec_sysfs.o
cros_ec_devs-objs := cros_ec_dev.o cros_ec_sysfs.o cros_ec_lightbar.o
obj-$(CONFIG_CROS_EC_CHARDEV) += cros_ec_devs.o
obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpc.o
......@@ -200,6 +200,7 @@ static int ec_device_probe(struct platform_device *pdev)
/* Initialize extra interfaces */
ec_dev_sysfs_init(ec);
ec_dev_lightbar_init(ec);
return 0;
}
......@@ -208,6 +209,7 @@ static int ec_device_remove(struct platform_device *pdev)
{
struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
ec_dev_lightbar_remove(ec);
ec_dev_sysfs_remove(ec);
device_destroy(cros_class, MKDEV(ec_major, 0));
cdev_del(&ec->cdev);
......
......@@ -47,4 +47,7 @@ struct cros_ec_readmem {
void ec_dev_sysfs_init(struct cros_ec_device *);
void ec_dev_sysfs_remove(struct cros_ec_device *);
void ec_dev_lightbar_init(struct cros_ec_device *);
void ec_dev_lightbar_remove(struct cros_ec_device *);
#endif /* _CROS_EC_DEV_H_ */
/*
* cros_ec_lightbar - expose the Chromebook Pixel lightbar to userspace
*
* Copyright (C) 2014 Google, Inc.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#define pr_fmt(fmt) "cros_ec_lightbar: " fmt
#include <linux/ctype.h>
#include <linux/delay.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/kobject.h>
#include <linux/mfd/cros_ec.h>
#include <linux/mfd/cros_ec_commands.h>
#include <linux/module.h>
#include <linux/platform_device.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/uaccess.h>
#include "cros_ec_dev.h"
/* Rate-limit the lightbar interface to prevent DoS. */
static unsigned long lb_interval_jiffies = 50 * HZ / 1000;
static ssize_t interval_msec_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
unsigned long msec = lb_interval_jiffies * 1000 / HZ;
return scnprintf(buf, PAGE_SIZE, "%lu\n", msec);
}
static ssize_t interval_msec_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
unsigned long msec;
if (kstrtoul(buf, 0, &msec))
return -EINVAL;
lb_interval_jiffies = msec * HZ / 1000;
return count;
}
static DEFINE_MUTEX(lb_mutex);
/* Return 0 if able to throttle correctly, error otherwise */
static int lb_throttle(void)
{
static unsigned long last_access;
unsigned long now, next_timeslot;
long delay;
int ret = 0;
mutex_lock(&lb_mutex);
now = jiffies;
next_timeslot = last_access + lb_interval_jiffies;
if (time_before(now, next_timeslot)) {
delay = (long)(next_timeslot) - (long)now;
set_current_state(TASK_INTERRUPTIBLE);
if (schedule_timeout(delay) > 0) {
/* interrupted - just abort */
ret = -EINTR;
goto out;
}
now = jiffies;
}
last_access = now;
out:
mutex_unlock(&lb_mutex);
return ret;
}
#define INIT_MSG(P, R) { \
.command = EC_CMD_LIGHTBAR_CMD, \
.outsize = sizeof(*P), \
.insize = sizeof(*R), \
}
static int get_lightbar_version(struct cros_ec_device *ec,
uint32_t *ver_ptr, uint32_t *flg_ptr)
{
struct ec_params_lightbar *param;
struct ec_response_lightbar *resp;
struct cros_ec_command msg = INIT_MSG(param, resp);
int ret;
param = (struct ec_params_lightbar *)msg.outdata;
param->cmd = LIGHTBAR_CMD_VERSION;
ret = cros_ec_cmd_xfer(ec, &msg);
if (ret < 0)
return 0;
switch (msg.result) {
case EC_RES_INVALID_PARAM:
/* Pixel had no version command. */
if (ver_ptr)
*ver_ptr = 0;
if (flg_ptr)
*flg_ptr = 0;
return 1;
case EC_RES_SUCCESS:
resp = (struct ec_response_lightbar *)msg.indata;
/* Future devices w/lightbars should implement this command */
if (ver_ptr)
*ver_ptr = resp->version.num;
if (flg_ptr)
*flg_ptr = resp->version.flags;
return 1;
}
/* Anything else (ie, EC_RES_INVALID_COMMAND) - no lightbar */
return 0;
}
static ssize_t version_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
uint32_t version, flags;
struct cros_ec_device *ec = dev_get_drvdata(dev);
int ret;
ret = lb_throttle();
if (ret)
return ret;
/* This should always succeed, because we check during init. */
if (!get_lightbar_version(ec, &version, &flags))
return -EIO;
return scnprintf(buf, PAGE_SIZE, "%d %d\n", version, flags);
}
static ssize_t brightness_store(struct device *dev,
struct device_attribute *attr,
const char *buf, size_t count)
{
struct ec_params_lightbar *param;
struct ec_response_lightbar *resp;
struct cros_ec_command msg = INIT_MSG(param, resp);
int ret;
unsigned int val;
struct cros_ec_device *ec = dev_get_drvdata(dev);
if (kstrtouint(buf, 0, &val))
return -EINVAL;
param = (struct ec_params_lightbar *)msg.outdata;
param->cmd = LIGHTBAR_CMD_BRIGHTNESS;
param->brightness.num = val;
ret = lb_throttle();
if (ret)
return ret;
ret = cros_ec_cmd_xfer(ec, &msg);
if (ret < 0)
return ret;
if (msg.result != EC_RES_SUCCESS)
return -EINVAL;
return count;
}
/*
* We expect numbers, and we'll keep reading until we find them, skipping over
* any whitespace (sysfs guarantees that the input is null-terminated). Every
* four numbers are sent to the lightbar as <LED,R,G,B>. We fail at the first
* parsing error, if we don't parse any numbers, or if we have numbers left
* over.
*/
static ssize_t led_rgb_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
struct ec_params_lightbar *param;
struct ec_response_lightbar *resp;
struct cros_ec_command msg = INIT_MSG(param, resp);
struct cros_ec_device *ec = dev_get_drvdata(dev);
unsigned int val[4];
int ret, i = 0, j = 0, ok = 0;
do {
/* Skip any whitespace */
while (*buf && isspace(*buf))
buf++;
if (!*buf)
break;
ret = sscanf(buf, "%i", &val[i++]);
if (ret == 0)
return -EINVAL;
if (i == 4) {
param = (struct ec_params_lightbar *)msg.outdata;
param->cmd = LIGHTBAR_CMD_RGB;
param->rgb.led = val[0];
param->rgb.red = val[1];
param->rgb.green = val[2];
param->rgb.blue = val[3];
/*
* Throttle only the first of every four transactions,
* so that the user can update all four LEDs at once.
*/
if ((j++ % 4) == 0) {
ret = lb_throttle();
if (ret)
return ret;
}
ret = cros_ec_cmd_xfer(ec, &msg);
if (ret < 0)
return ret;
if (msg.result != EC_RES_SUCCESS)
return -EINVAL;
i = 0;
ok = 1;
}
/* Skip over the number we just read */
while (*buf && !isspace(*buf))
buf++;
} while (*buf);
return (ok && i == 0) ? count : -EINVAL;
}
static const char const *seqname[] = {
"ERROR", "S5", "S3", "S0", "S5S3", "S3S0",
"S0S3", "S3S5", "STOP", "RUN", "PULSE", "TEST", "KONAMI",
};
static ssize_t sequence_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
struct ec_params_lightbar *param;
struct ec_response_lightbar *resp;
struct cros_ec_command msg = INIT_MSG(param, resp);
int ret;
struct cros_ec_device *ec = dev_get_drvdata(dev);
param = (struct ec_params_lightbar *)msg.outdata;
param->cmd = LIGHTBAR_CMD_GET_SEQ;
ret = lb_throttle();
if (ret)
return ret;
ret = cros_ec_cmd_xfer(ec, &msg);
if (ret < 0)
return ret;
if (msg.result != EC_RES_SUCCESS)
return scnprintf(buf, PAGE_SIZE,
"ERROR: EC returned %d\n", msg.result);
resp = (struct ec_response_lightbar *)msg.indata;
if (resp->get_seq.num >= ARRAY_SIZE(seqname))
return scnprintf(buf, PAGE_SIZE, "%d\n", resp->get_seq.num);
else
return scnprintf(buf, PAGE_SIZE, "%s\n",
seqname[resp->get_seq.num]);
}
static ssize_t sequence_store(struct device *dev, struct device_attribute *attr,
const char *buf, size_t count)
{
struct ec_params_lightbar *param;
struct ec_response_lightbar *resp;
struct cros_ec_command msg = INIT_MSG(param, resp);
unsigned int num;
int ret, len;
struct cros_ec_device *ec = dev_get_drvdata(dev);
for (len = 0; len < count; len++)
if (!isalnum(buf[len]))
break;
for (num = 0; num < ARRAY_SIZE(seqname); num++)
if (!strncasecmp(seqname[num], buf, len))
break;
if (num >= ARRAY_SIZE(seqname)) {
ret = kstrtouint(buf, 0, &num);
if (ret)
return ret;
}
param = (struct ec_params_lightbar *)msg.outdata;
param->cmd = LIGHTBAR_CMD_SEQ;
param->seq.num = num;
ret = lb_throttle();
if (ret)
return ret;
ret = cros_ec_cmd_xfer(ec, &msg);
if (ret < 0)
return ret;
if (msg.result != EC_RES_SUCCESS)
return -EINVAL;
return count;
}
/* Module initialization */
static DEVICE_ATTR_RW(interval_msec);
static DEVICE_ATTR_RO(version);
static DEVICE_ATTR_WO(brightness);
static DEVICE_ATTR_WO(led_rgb);
static DEVICE_ATTR_RW(sequence);
static struct attribute *__lb_cmds_attrs[] = {
&dev_attr_interval_msec.attr,
&dev_attr_version.attr,
&dev_attr_brightness.attr,
&dev_attr_led_rgb.attr,
&dev_attr_sequence.attr,
NULL,
};
static struct attribute_group lb_cmds_attr_group = {
.name = "lightbar",
.attrs = __lb_cmds_attrs,
};
void ec_dev_lightbar_init(struct cros_ec_device *ec)
{
int ret = 0;
/* Only instantiate this stuff if the EC has a lightbar */
if (!get_lightbar_version(ec, NULL, NULL))
return;
ret = sysfs_create_group(&ec->vdev->kobj, &lb_cmds_attr_group);
if (ret)
pr_warn("sysfs_create_group() failed: %d\n", ret);
}
void ec_dev_lightbar_remove(struct cros_ec_device *ec)
{
sysfs_remove_group(&ec->vdev->kobj, &lb_cmds_attr_group);
}
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