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    Subject[PATCH v2 2/3] platform/chrome: Support reading/writing the vboot context
    Date
    Some EC implementations include a small nvram space used to store
    verified boot context data. This patch offers a way to expose this
    data to userspace.

    Signed-off-by: Emilio López <emilio.lopez@collabora.co.uk>
    ---
    Changes from v1:
    - Use is_bin_visible instead of is_visible

    Documentation/devicetree/bindings/mfd/cros-ec.txt | 4 +
    drivers/platform/chrome/Makefile | 5 +-
    drivers/platform/chrome/cros_ec_dev.c | 1 +
    drivers/platform/chrome/cros_ec_vbc.c | 137 ++++++++++++++++++++++
    include/linux/mfd/cros_ec.h | 1 +
    5 files changed, 147 insertions(+), 1 deletion(-)
    create mode 100644 drivers/platform/chrome/cros_ec_vbc.c

    diff --git a/Documentation/devicetree/bindings/mfd/cros-ec.txt b/Documentation/devicetree/bindings/mfd/cros-ec.txt
    index 1777916..136e0c2 100644
    --- a/Documentation/devicetree/bindings/mfd/cros-ec.txt
    +++ b/Documentation/devicetree/bindings/mfd/cros-ec.txt
    @@ -34,6 +34,10 @@ Required properties (LPC):
    - compatible: "google,cros-ec-lpc"
    - reg: List of (IO address, size) pairs defining the interface uses

    +Optional properties (all):
    +- google,has-vbc-nvram: Some implementations of the EC include a small
    + nvram space used to store verified boot context data. This boolean flag
    + is used to specify whether this nvram is present or not.

    Example for I2C:

    diff --git a/drivers/platform/chrome/Makefile b/drivers/platform/chrome/Makefile
    index 4a11b01..787be61 100644
    --- a/drivers/platform/chrome/Makefile
    +++ b/drivers/platform/chrome/Makefile
    @@ -1,7 +1,10 @@

    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_lightbar.o
    +cros_ec_devs-objs := cros_ec_dev.o
    +cros_ec_devs-objs += cros_ec_lightbar.o
    +cros_ec_devs-objs += cros_ec_sysfs.o
    +cros_ec_devs-objs += cros_ec_vbc.o
    obj-$(CONFIG_CROS_EC_CHARDEV) += cros_ec_devs.o
    obj-$(CONFIG_CROS_EC_LPC) += cros_ec_lpc.o
    obj-$(CONFIG_CROS_EC_PROTO) += cros_ec_proto.o
    diff --git a/drivers/platform/chrome/cros_ec_dev.c b/drivers/platform/chrome/cros_ec_dev.c
    index e8fcdc2..d19263f 100644
    --- a/drivers/platform/chrome/cros_ec_dev.c
    +++ b/drivers/platform/chrome/cros_ec_dev.c
    @@ -32,6 +32,7 @@ static int ec_major;
    static const struct attribute_group *cros_ec_groups[] = {
    &cros_ec_attr_group,
    &cros_ec_lightbar_attr_group,
    + &cros_ec_vbc_attr_group,
    NULL,
    };

    diff --git a/drivers/platform/chrome/cros_ec_vbc.c b/drivers/platform/chrome/cros_ec_vbc.c
    new file mode 100644
    index 0000000..a0e8d38
    --- /dev/null
    +++ b/drivers/platform/chrome/cros_ec_vbc.c
    @@ -0,0 +1,137 @@
    +/*
    + * cros_ec_vbc - Expose the vboot context nvram to userspace
    + *
    + * Copyright (C) 2015 Collabora Ltd.
    + *
    + * based on vendor driver,
    + *
    + * Copyright (C) 2012 The Chromium OS Authors
    + *
    + * 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.
    + */
    +
    +#include <linux/of.h>
    +#include <linux/platform_device.h>
    +#include <linux/mfd/cros_ec.h>
    +#include <linux/mfd/cros_ec_commands.h>
    +#include <linux/slab.h>
    +
    +static ssize_t vboot_context_read(struct file *filp, struct kobject *kobj,
    + struct bin_attribute *att, char *buf,
    + loff_t pos, size_t count)
    +{
    + struct device *dev = container_of(kobj, struct device, kobj);
    + struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
    + class_dev);
    + struct cros_ec_device *ecdev = ec->ec_dev;
    + struct ec_params_vbnvcontext *params;
    + struct cros_ec_command *msg;
    + int err;
    + const size_t para_sz = sizeof(struct ec_params_vbnvcontext);
    + const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
    + const size_t payload = max(para_sz, resp_sz);
    +
    + msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
    + if (!msg)
    + return -ENOMEM;
    +
    + params = (struct ec_params_vbnvcontext *)msg->data;
    + params->op = EC_VBNV_CONTEXT_OP_READ;
    +
    + msg->version = EC_VER_VBNV_CONTEXT;
    + msg->command = EC_CMD_VBNV_CONTEXT;
    + msg->outsize = sizeof(params->op);
    + msg->insize = resp_sz;
    +
    + err = cros_ec_cmd_xfer(ecdev, msg);
    + if (err < 0) {
    + dev_err(dev, "Error sending read request: %d\n", err);
    + kfree(msg);
    + return err;
    + }
    +
    + BUILD_BUG_ON(resp_sz > PAGE_SIZE);
    + memcpy(buf, msg->data, resp_sz);
    +
    + kfree(msg);
    + return resp_sz;
    +}
    +
    +static ssize_t vboot_context_write(struct file *filp, struct kobject *kobj,
    + struct bin_attribute *attr, char *buf,
    + loff_t pos, size_t count)
    +{
    + struct device *dev = container_of(kobj, struct device, kobj);
    + struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
    + class_dev);
    + struct cros_ec_device *ecdev = ec->ec_dev;
    + struct ec_params_vbnvcontext *params;
    + struct cros_ec_command *msg;
    + int err;
    + const size_t para_sz = sizeof(*params);
    + const size_t data_sz = sizeof(params->block);
    +
    + /* Only write full values */
    + if (count != data_sz)
    + return -EINVAL;
    +
    + msg = kmalloc(sizeof(*msg) + para_sz, GFP_KERNEL);
    + if (!msg)
    + return -ENOMEM;
    +
    + params = (struct ec_params_vbnvcontext *)msg->data;
    + params->op = EC_VBNV_CONTEXT_OP_WRITE;
    + memcpy(params->block, buf, data_sz);
    +
    + msg->version = EC_VER_VBNV_CONTEXT;
    + msg->command = EC_CMD_VBNV_CONTEXT;
    + msg->outsize = para_sz;
    + msg->insize = 0;
    +
    + err = cros_ec_cmd_xfer(ecdev, msg);
    + if (err < 0) {
    + dev_err(dev, "Error sending write request: %d\n", err);
    + kfree(msg);
    + return err;
    + }
    +
    + kfree(msg);
    + return data_sz;
    +}
    +
    +static umode_t cros_ec_vbc_is_visible(struct kobject *kobj,
    + struct bin_attribute *a, int n)
    +{
    + struct device *dev = container_of(kobj, struct device, kobj);
    + struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
    + class_dev);
    + struct device_node *np = ec->ec_dev->dev->of_node;
    +
    + if (IS_ENABLED(CONFIG_OF) && np) {
    + if (of_property_read_bool(np, "google,has-vbc-nvram"))
    + return a->attr.mode;
    + }
    +
    + return 0;
    +}
    +
    +static BIN_ATTR_RW(vboot_context, 16);
    +
    +static struct bin_attribute *cros_ec_vbc_bin_attrs[] = {
    + &bin_attr_vboot_context,
    + NULL
    +};
    +
    +struct attribute_group cros_ec_vbc_attr_group = {
    + .name = "vbc",
    + .bin_attrs = cros_ec_vbc_bin_attrs,
    + .is_bin_visible = cros_ec_vbc_is_visible,
    +};
    diff --git a/include/linux/mfd/cros_ec.h b/include/linux/mfd/cros_ec.h
    index da72671..494682c 100644
    --- a/include/linux/mfd/cros_ec.h
    +++ b/include/linux/mfd/cros_ec.h
    @@ -255,5 +255,6 @@ int cros_ec_query_all(struct cros_ec_device *ec_dev);
    /* sysfs stuff */
    extern struct attribute_group cros_ec_attr_group;
    extern struct attribute_group cros_ec_lightbar_attr_group;
    +extern struct attribute_group cros_ec_vbc_attr_group;

    #endif /* __LINUX_MFD_CROS_EC_H */
    --
    2.1.4


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