drivers/platform/chrome/cros_ec_vbc.c

   1 /*
   2  * cros_ec_vbc - Expose the vboot context nvram to userspace
   3  *
   4  * Copyright (C) 2015 Collabora Ltd.
   5  *
   6  * based on vendor driver,
   7  *
   8  * Copyright (C) 2012 The Chromium OS Authors
   9  *
  10  * This program is free software; you can redistribute it and/or modify
  11  * it under the terms of the GNU General Public License as published by
  12  * the Free Software Foundation; either version 2 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18  * GNU General Public License for more details.
  19  */
  20
  21 #include <linux/of.h>
  22 #include <linux/platform_device.h>
  23 #include <linux/mfd/cros_ec.h>
  24 #include <linux/mfd/cros_ec_commands.h>
  25 #include <linux/slab.h>
  26
  27 static ssize_t vboot_context_read(struct file *filp, struct kobject *kobj,
  28                                   struct bin_attribute *att, char *buf,
  29                                   loff_t pos, size_t count)
  30 {
  31         struct device *dev = container_of(kobj, struct device, kobj);
  32         struct cros_ec_dev *ec = to_cros_ec_dev(dev);
  33         struct cros_ec_device *ecdev = ec->ec_dev;
  34         struct ec_params_vbnvcontext *params;
  35         struct cros_ec_command *msg;
  36         int err;
  37         const size_t para_sz = sizeof(params->op);
  38         const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
  39         const size_t payload = max(para_sz, resp_sz);
  40
  41         msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
  42         if (!msg)
  43                 return -ENOMEM;
  44
  45         /* NB: we only kmalloc()ated enough space for the op field */
  46         params = (struct ec_params_vbnvcontext *)msg->data;
  47         params->op = EC_VBNV_CONTEXT_OP_READ;
  48
  49         msg->version = EC_VER_VBNV_CONTEXT;
  50         msg->command = EC_CMD_VBNV_CONTEXT;
  51         msg->outsize = para_sz;
  52         msg->insize = resp_sz;
  53
  54         err = cros_ec_cmd_xfer(ecdev, msg);
  55         if (err < 0) {
  56                 dev_err(dev, "Error sending read request: %d\n", err);
  57                 kfree(msg);
  58                 return err;
  59         }
  60
  61         memcpy(buf, msg->data, resp_sz);
  62
  63         kfree(msg);
  64         return resp_sz;
  65 }
  66
  67 static ssize_t vboot_context_write(struct file *filp, struct kobject *kobj,
  68                                    struct bin_attribute *attr, char *buf,
  69                                    loff_t pos, size_t count)
  70 {
  71         struct device *dev = container_of(kobj, struct device, kobj);
  72         struct cros_ec_dev *ec = to_cros_ec_dev(dev);
  73         struct cros_ec_device *ecdev = ec->ec_dev;
  74         struct ec_params_vbnvcontext *params;
  75         struct cros_ec_command *msg;
  76         int err;
  77         const size_t para_sz = sizeof(*params);
  78         const size_t data_sz = sizeof(params->block);
  79
  80         /* Only write full values */
  81         if (count != data_sz)
  82                 return -EINVAL;
  83
  84         msg = kmalloc(sizeof(*msg) + para_sz, GFP_KERNEL);
  85         if (!msg)
  86                 return -ENOMEM;
  87
  88         params = (struct ec_params_vbnvcontext *)msg->data;
  89         params->op = EC_VBNV_CONTEXT_OP_WRITE;
  90         memcpy(params->block, buf, data_sz);
  91
  92         msg->version = EC_VER_VBNV_CONTEXT;
  93         msg->command = EC_CMD_VBNV_CONTEXT;
  94         msg->outsize = para_sz;
  95         msg->insize = 0;
  96
  97         err = cros_ec_cmd_xfer(ecdev, msg);
  98         if (err < 0) {
  99                 dev_err(dev, "Error sending write request: %d\n", err);
 100                 kfree(msg);
 101                 return err;
 102         }
 103
 104         kfree(msg);
 105         return data_sz;
 106 }
 107
 108 static umode_t cros_ec_vbc_is_visible(struct kobject *kobj,
 109                                       struct bin_attribute *a, int n)
 110 {
 111         struct device *dev = container_of(kobj, struct device, kobj);
 112         struct cros_ec_dev *ec = to_cros_ec_dev(dev);
 113         struct device_node *np = ec->ec_dev->dev->of_node;
 114
 115         if (IS_ENABLED(CONFIG_OF) && np) {
 116                 if (of_property_read_bool(np, "google,has-vbc-nvram"))
 117                         return a->attr.mode;
 118         }
 119
 120         return 0;
 121 }
 122
 123 static BIN_ATTR_RW(vboot_context, 16);
 124
 125 static struct bin_attribute *cros_ec_vbc_bin_attrs[] = {
 126         &bin_attr_vboot_context,
 127         NULL
 128 };
 129
 130 struct attribute_group cros_ec_vbc_attr_group = {
 131         .name = "vbc",
 132         .bin_attrs = cros_ec_vbc_bin_attrs,
 133         .is_bin_visible = cros_ec_vbc_is_visible,
 134 };
 135 EXPORT_SYMBOL(cros_ec_vbc_attr_group);