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 = container_of(dev, struct cros_ec_dev,
  33                                               class_dev);
  34         struct cros_ec_device *ecdev = ec->ec_dev;
  35         struct ec_params_vbnvcontext *params;
  36         struct cros_ec_command *msg;
  37         int err;
  38         const size_t para_sz = sizeof(params->op);
  39         const size_t resp_sz = sizeof(struct ec_response_vbnvcontext);
  40         const size_t payload = max(para_sz, resp_sz);
  41
  42         msg = kmalloc(sizeof(*msg) + payload, GFP_KERNEL);
  43         if (!msg)
  44                 return -ENOMEM;
  45
  46         /* NB: we only kmalloc()ated enough space for the op field */
  47         params = (struct ec_params_vbnvcontext *)msg->data;
  48         params->op = EC_VBNV_CONTEXT_OP_READ;
  49
  50         msg->version = EC_VER_VBNV_CONTEXT;
  51         msg->command = EC_CMD_VBNV_CONTEXT;
  52         msg->outsize = para_sz;
  53         msg->insize = resp_sz;
  54
  55         err = cros_ec_cmd_xfer(ecdev, msg);
  56         if (err < 0) {
  57                 dev_err(dev, "Error sending read request: %d\n", err);
  58                 kfree(msg);
  59                 return err;
  60         }
  61
  62         memcpy(buf, msg->data, resp_sz);
  63
  64         kfree(msg);
  65         return resp_sz;
  66 }
  67
  68 static ssize_t vboot_context_write(struct file *filp, struct kobject *kobj,
  69                                    struct bin_attribute *attr, char *buf,
  70                                    loff_t pos, size_t count)
  71 {
  72         struct device *dev = container_of(kobj, struct device, kobj);
  73         struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
  74                                               class_dev);
  75         struct cros_ec_device *ecdev = ec->ec_dev;
  76         struct ec_params_vbnvcontext *params;
  77         struct cros_ec_command *msg;
  78         int err;
  79         const size_t para_sz = sizeof(*params);
  80         const size_t data_sz = sizeof(params->block);
  81
  82         /* Only write full values */
  83         if (count != data_sz)
  84                 return -EINVAL;
  85
  86         msg = kmalloc(sizeof(*msg) + para_sz, GFP_KERNEL);
  87         if (!msg)
  88                 return -ENOMEM;
  89
  90         params = (struct ec_params_vbnvcontext *)msg->data;
  91         params->op = EC_VBNV_CONTEXT_OP_WRITE;
  92         memcpy(params->block, buf, data_sz);
  93
  94         msg->version = EC_VER_VBNV_CONTEXT;
  95         msg->command = EC_CMD_VBNV_CONTEXT;
  96         msg->outsize = para_sz;
  97         msg->insize = 0;
  98
  99         err = cros_ec_cmd_xfer(ecdev, msg);
 100         if (err < 0) {
 101                 dev_err(dev, "Error sending write request: %d\n", err);
 102                 kfree(msg);
 103                 return err;
 104         }
 105
 106         kfree(msg);
 107         return data_sz;
 108 }
 109
 110 static umode_t cros_ec_vbc_is_visible(struct kobject *kobj,
 111                                       struct bin_attribute *a, int n)
 112 {
 113         struct device *dev = container_of(kobj, struct device, kobj);
 114         struct cros_ec_dev *ec = container_of(dev, struct cros_ec_dev,
 115                                               class_dev);
 116         struct device_node *np = ec->ec_dev->dev->of_node;
 117
 118         if (IS_ENABLED(CONFIG_OF) && np) {
 119                 if (of_property_read_bool(np, "google,has-vbc-nvram"))
 120                         return a->attr.mode;
 121         }
 122
 123         return 0;
 124 }
 125
 126 static BIN_ATTR_RW(vboot_context, 16);
 127
 128 static struct bin_attribute *cros_ec_vbc_bin_attrs[] = {
 129         &bin_attr_vboot_context,
 130         NULL
 131 };
 132
 133 struct attribute_group cros_ec_vbc_attr_group = {
 134         .name = "vbc",
 135         .bin_attrs = cros_ec_vbc_bin_attrs,
 136         .is_bin_visible = cros_ec_vbc_is_visible,
 137 };