From f3f837e52b14bf84c2db65f622b5c31cd261100c Mon Sep 17 00:00:00 2001 From: Bill Richardson Date: Mon, 2 Feb 2015 12:26:28 +0100 Subject: [PATCH] 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 Reviewed-by: Olof Johansson Tested-by: Doug Anderson Reviewed-by: Benson Leung Signed-off-by: Javier Martinez Canillas Tested-by: Gwendal Grignou Reviewed-by: Gwendal Grignou Signed-off-by: Olof Johansson --- drivers/platform/chrome/Makefile | 2 +- drivers/platform/chrome/cros_ec_dev.c | 2 + drivers/platform/chrome/cros_ec_dev.h | 3 + drivers/platform/chrome/cros_ec_lightbar.c | 367 +++++++++++++++++++++ 4 files changed, 373 insertions(+), 1 deletion(-) create mode 100644 drivers/platform/chrome/cros_ec_lightbar.c diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile index 34b631ceff67..bd8d8601e875 100644 --- a/drivers/platform/chrome/Makefile +++ b/drivers/platform/chrome/Makefile @@ -1,6 +1,6 @@ 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 diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c index 33f37ad36892..ce714317a59e 100644 --- a/drivers/platform/chrome/cros_ec_dev.c +++ b/drivers/platform/chrome/cros_ec_dev.c @@ -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); diff --git a/drivers/platform/chrome/cros_ec_dev.h b/drivers/platform/chrome/cros_ec_dev.h index f03613290ecf..45d67f7e518c 100644 --- a/drivers/platform/chrome/cros_ec_dev.h +++ b/drivers/platform/chrome/cros_ec_dev.h @@ -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_ */ diff --git a/drivers/platform/chrome/cros_ec_lightbar.c b/drivers/platform/chrome/cros_ec_lightbar.c new file mode 100644 index 000000000000..35fc892e4c95 --- /dev/null +++ b/drivers/platform/chrome/cros_ec_lightbar.c @@ -0,0 +1,367 @@ +/* + * 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 . + */ + +#define pr_fmt(fmt) "cros_ec_lightbar: " fmt + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#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 . 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); +} -- 2.39.2