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: Bill Richardson <wfrichar@chromium.org>
Reviewed-by: Olof Johansson <olofj@chromium.org>
Tested-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Tested-by: Gwendal Grignou <gwendal@chromium.org>
Reviewed-by: Gwendal Grignou <gwendal@chromium.org>
Signed-off-by: Olof Johansson <olof@lixom.net>
This commit is contained in:
Bill Richardson
Olof Johansson
parent
71af4b52cc
commit
f3f837e52b
@ -1,6 +1,6 @@
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obj-$(CONFIG_CHROMEOS_LAPTOP) += chromeos_laptop.o
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obj-$(CONFIG_CHROMEOS_PSTORE) += chromeos_pstore.o
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cros_ec_devs-objs := cros_ec_dev.o cros_ec_sysfs.o
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cros_ec_devs-objs := cros_ec_dev.o cros_ec_sysfs.o cros_ec_lightbar.o
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obj-$(CONFIG_CROS_EC_CHARDEV) += cros_ec_devs.o
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obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpc.o
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@ -200,6 +200,7 @@ static int ec_device_probe(struct platform_device *pdev)
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/* Initialize extra interfaces */
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ec_dev_sysfs_init(ec);
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ec_dev_lightbar_init(ec);
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return 0;
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}
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@ -208,6 +209,7 @@ static int ec_device_remove(struct platform_device *pdev)
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{
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struct cros_ec_device *ec = dev_get_drvdata(pdev->dev.parent);
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ec_dev_lightbar_remove(ec);
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ec_dev_sysfs_remove(ec);
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device_destroy(cros_class, MKDEV(ec_major, 0));
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cdev_del(&ec->cdev);
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@ -47,4 +47,7 @@ struct cros_ec_readmem {
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void ec_dev_sysfs_init(struct cros_ec_device *);
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void ec_dev_sysfs_remove(struct cros_ec_device *);
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void ec_dev_lightbar_init(struct cros_ec_device *);
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void ec_dev_lightbar_remove(struct cros_ec_device *);
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#endif /* _CROS_EC_DEV_H_ */
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367
drivers/platform/chrome/cros_ec_lightbar.c
Normal file
367
drivers/platform/chrome/cros_ec_lightbar.c
Normal file
@ -0,0 +1,367 @@
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/*
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* cros_ec_lightbar - expose the Chromebook Pixel lightbar to userspace
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*
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* Copyright (C) 2014 Google, Inc.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#define pr_fmt(fmt) "cros_ec_lightbar: " fmt
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#include <linux/ctype.h>
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#include <linux/delay.h>
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#include <linux/device.h>
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#include <linux/fs.h>
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#include <linux/kobject.h>
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#include <linux/mfd/cros_ec.h>
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#include <linux/mfd/cros_ec_commands.h>
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#include <linux/module.h>
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#include <linux/platform_device.h>
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#include <linux/sched.h>
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#include <linux/types.h>
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#include <linux/uaccess.h>
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#include "cros_ec_dev.h"
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/* Rate-limit the lightbar interface to prevent DoS. */
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static unsigned long lb_interval_jiffies = 50 * HZ / 1000;
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static ssize_t interval_msec_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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unsigned long msec = lb_interval_jiffies * 1000 / HZ;
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return scnprintf(buf, PAGE_SIZE, "%lu\n", msec);
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}
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static ssize_t interval_msec_store(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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unsigned long msec;
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if (kstrtoul(buf, 0, &msec))
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return -EINVAL;
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lb_interval_jiffies = msec * HZ / 1000;
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return count;
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}
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static DEFINE_MUTEX(lb_mutex);
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/* Return 0 if able to throttle correctly, error otherwise */
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static int lb_throttle(void)
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{
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static unsigned long last_access;
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unsigned long now, next_timeslot;
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long delay;
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int ret = 0;
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mutex_lock(&lb_mutex);
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now = jiffies;
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next_timeslot = last_access + lb_interval_jiffies;
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if (time_before(now, next_timeslot)) {
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delay = (long)(next_timeslot) - (long)now;
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set_current_state(TASK_INTERRUPTIBLE);
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if (schedule_timeout(delay) > 0) {
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/* interrupted - just abort */
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ret = -EINTR;
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goto out;
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}
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now = jiffies;
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}
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last_access = now;
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out:
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mutex_unlock(&lb_mutex);
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return ret;
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}
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#define INIT_MSG(P, R) { \
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.command = EC_CMD_LIGHTBAR_CMD, \
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.outsize = sizeof(*P), \
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.insize = sizeof(*R), \
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}
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static int get_lightbar_version(struct cros_ec_device *ec,
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uint32_t *ver_ptr, uint32_t *flg_ptr)
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{
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struct ec_params_lightbar *param;
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struct ec_response_lightbar *resp;
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struct cros_ec_command msg = INIT_MSG(param, resp);
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int ret;
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param = (struct ec_params_lightbar *)msg.outdata;
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param->cmd = LIGHTBAR_CMD_VERSION;
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ret = cros_ec_cmd_xfer(ec, &msg);
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if (ret < 0)
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return 0;
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switch (msg.result) {
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case EC_RES_INVALID_PARAM:
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/* Pixel had no version command. */
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if (ver_ptr)
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*ver_ptr = 0;
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if (flg_ptr)
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*flg_ptr = 0;
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return 1;
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case EC_RES_SUCCESS:
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resp = (struct ec_response_lightbar *)msg.indata;
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/* Future devices w/lightbars should implement this command */
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if (ver_ptr)
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*ver_ptr = resp->version.num;
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if (flg_ptr)
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*flg_ptr = resp->version.flags;
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return 1;
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}
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/* Anything else (ie, EC_RES_INVALID_COMMAND) - no lightbar */
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return 0;
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}
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static ssize_t version_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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uint32_t version, flags;
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struct cros_ec_device *ec = dev_get_drvdata(dev);
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int ret;
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ret = lb_throttle();
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if (ret)
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return ret;
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/* This should always succeed, because we check during init. */
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if (!get_lightbar_version(ec, &version, &flags))
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return -EIO;
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return scnprintf(buf, PAGE_SIZE, "%d %d\n", version, flags);
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}
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static ssize_t brightness_store(struct device *dev,
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struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct ec_params_lightbar *param;
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struct ec_response_lightbar *resp;
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struct cros_ec_command msg = INIT_MSG(param, resp);
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int ret;
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unsigned int val;
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struct cros_ec_device *ec = dev_get_drvdata(dev);
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if (kstrtouint(buf, 0, &val))
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return -EINVAL;
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param = (struct ec_params_lightbar *)msg.outdata;
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param->cmd = LIGHTBAR_CMD_BRIGHTNESS;
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param->brightness.num = val;
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ret = lb_throttle();
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if (ret)
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return ret;
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ret = cros_ec_cmd_xfer(ec, &msg);
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if (ret < 0)
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return ret;
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if (msg.result != EC_RES_SUCCESS)
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return -EINVAL;
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return count;
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}
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/*
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* We expect numbers, and we'll keep reading until we find them, skipping over
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* any whitespace (sysfs guarantees that the input is null-terminated). Every
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* four numbers are sent to the lightbar as <LED,R,G,B>. We fail at the first
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* parsing error, if we don't parse any numbers, or if we have numbers left
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* over.
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*/
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static ssize_t led_rgb_store(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct ec_params_lightbar *param;
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struct ec_response_lightbar *resp;
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struct cros_ec_command msg = INIT_MSG(param, resp);
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struct cros_ec_device *ec = dev_get_drvdata(dev);
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unsigned int val[4];
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int ret, i = 0, j = 0, ok = 0;
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do {
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/* Skip any whitespace */
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while (*buf && isspace(*buf))
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buf++;
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if (!*buf)
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break;
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ret = sscanf(buf, "%i", &val[i++]);
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if (ret == 0)
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return -EINVAL;
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if (i == 4) {
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param = (struct ec_params_lightbar *)msg.outdata;
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param->cmd = LIGHTBAR_CMD_RGB;
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param->rgb.led = val[0];
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param->rgb.red = val[1];
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param->rgb.green = val[2];
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param->rgb.blue = val[3];
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/*
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* Throttle only the first of every four transactions,
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* so that the user can update all four LEDs at once.
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*/
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if ((j++ % 4) == 0) {
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ret = lb_throttle();
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if (ret)
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return ret;
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}
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ret = cros_ec_cmd_xfer(ec, &msg);
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if (ret < 0)
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return ret;
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if (msg.result != EC_RES_SUCCESS)
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return -EINVAL;
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i = 0;
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ok = 1;
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}
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/* Skip over the number we just read */
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while (*buf && !isspace(*buf))
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buf++;
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} while (*buf);
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return (ok && i == 0) ? count : -EINVAL;
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}
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static const char const *seqname[] = {
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"ERROR", "S5", "S3", "S0", "S5S3", "S3S0",
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"S0S3", "S3S5", "STOP", "RUN", "PULSE", "TEST", "KONAMI",
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};
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static ssize_t sequence_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct ec_params_lightbar *param;
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struct ec_response_lightbar *resp;
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struct cros_ec_command msg = INIT_MSG(param, resp);
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int ret;
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struct cros_ec_device *ec = dev_get_drvdata(dev);
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param = (struct ec_params_lightbar *)msg.outdata;
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param->cmd = LIGHTBAR_CMD_GET_SEQ;
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ret = lb_throttle();
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if (ret)
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return ret;
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ret = cros_ec_cmd_xfer(ec, &msg);
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if (ret < 0)
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return ret;
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if (msg.result != EC_RES_SUCCESS)
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return scnprintf(buf, PAGE_SIZE,
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"ERROR: EC returned %d\n", msg.result);
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resp = (struct ec_response_lightbar *)msg.indata;
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if (resp->get_seq.num >= ARRAY_SIZE(seqname))
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return scnprintf(buf, PAGE_SIZE, "%d\n", resp->get_seq.num);
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else
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return scnprintf(buf, PAGE_SIZE, "%s\n",
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seqname[resp->get_seq.num]);
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}
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static ssize_t sequence_store(struct device *dev, struct device_attribute *attr,
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const char *buf, size_t count)
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{
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struct ec_params_lightbar *param;
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struct ec_response_lightbar *resp;
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struct cros_ec_command msg = INIT_MSG(param, resp);
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unsigned int num;
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int ret, len;
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struct cros_ec_device *ec = dev_get_drvdata(dev);
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for (len = 0; len < count; len++)
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if (!isalnum(buf[len]))
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break;
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for (num = 0; num < ARRAY_SIZE(seqname); num++)
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if (!strncasecmp(seqname[num], buf, len))
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break;
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if (num >= ARRAY_SIZE(seqname)) {
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ret = kstrtouint(buf, 0, &num);
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if (ret)
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return ret;
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}
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param = (struct ec_params_lightbar *)msg.outdata;
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param->cmd = LIGHTBAR_CMD_SEQ;
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param->seq.num = num;
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ret = lb_throttle();
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if (ret)
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return ret;
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ret = cros_ec_cmd_xfer(ec, &msg);
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if (ret < 0)
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return ret;
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if (msg.result != EC_RES_SUCCESS)
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return -EINVAL;
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return count;
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}
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/* Module initialization */
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static DEVICE_ATTR_RW(interval_msec);
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static DEVICE_ATTR_RO(version);
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static DEVICE_ATTR_WO(brightness);
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static DEVICE_ATTR_WO(led_rgb);
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static DEVICE_ATTR_RW(sequence);
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static struct attribute *__lb_cmds_attrs[] = {
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&dev_attr_interval_msec.attr,
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&dev_attr_version.attr,
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&dev_attr_brightness.attr,
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&dev_attr_led_rgb.attr,
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&dev_attr_sequence.attr,
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NULL,
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};
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static struct attribute_group lb_cmds_attr_group = {
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.name = "lightbar",
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.attrs = __lb_cmds_attrs,
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};
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void ec_dev_lightbar_init(struct cros_ec_device *ec)
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{
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int ret = 0;
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/* Only instantiate this stuff if the EC has a lightbar */
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if (!get_lightbar_version(ec, NULL, NULL))
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return;
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ret = sysfs_create_group(&ec->vdev->kobj, &lb_cmds_attr_group);
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if (ret)
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pr_warn("sysfs_create_group() failed: %d\n", ret);
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}
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void ec_dev_lightbar_remove(struct cros_ec_device *ec)
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{
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sysfs_remove_group(&ec->vdev->kobj, &lb_cmds_attr_group);
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}
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