drivers/char/powernv-op-panel.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * OPAL Operator Panel Display Driver
   4  *
   5  * Copyright 2016, Suraj Jitindar Singh, IBM Corporation.
   6  */
   7
   8 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
   9
  10 #include <linux/init.h>
  11 #include <linux/module.h>
  12 #include <linux/kernel.h>
  13 #include <linux/fs.h>
  14 #include <linux/device.h>
  15 #include <linux/errno.h>
  16 #include <linux/mutex.h>
  17 #include <linux/of.h>
  18 #include <linux/slab.h>
  19 #include <linux/platform_device.h>
  20 #include <linux/miscdevice.h>
  21
  22 #include <asm/opal.h>
  23
  24 /*
  25  * This driver creates a character device (/dev/op_panel) which exposes the
  26  * operator panel (character LCD display) on IBM Power Systems machines
  27  * with FSPs.
  28  * A character buffer written to the device will be displayed on the
  29  * operator panel.
  30  */
  31
  32 static DEFINE_MUTEX(oppanel_mutex);
  33
  34 static u32              num_lines, oppanel_size;
  35 static oppanel_line_t   *oppanel_lines;
  36 static char             *oppanel_data;
  37
  38 static loff_t oppanel_llseek(struct file *filp, loff_t offset, int whence)
  39 {
  40         return fixed_size_llseek(filp, offset, whence, oppanel_size);
  41 }
  42
  43 static ssize_t oppanel_read(struct file *filp, char __user *userbuf, size_t len,
  44                             loff_t *f_pos)
  45 {
  46         return simple_read_from_buffer(userbuf, len, f_pos, oppanel_data,
  47                         oppanel_size);
  48 }
  49
  50 static int __op_panel_update_display(void)
  51 {
  52         struct opal_msg msg;
  53         int rc, token;
  54
  55         token = opal_async_get_token_interruptible();
  56         if (token < 0) {
  57                 if (token != -ERESTARTSYS)
  58                         pr_debug("Couldn't get OPAL async token [token=%d]\n",
  59                                 token);
  60                 return token;
  61         }
  62
  63         rc = opal_write_oppanel_async(token, oppanel_lines, num_lines);
  64         switch (rc) {
  65         case OPAL_ASYNC_COMPLETION:
  66                 rc = opal_async_wait_response(token, &msg);
  67                 if (rc) {
  68                         pr_debug("Failed to wait for async response [rc=%d]\n",
  69                                 rc);
  70                         break;
  71                 }
  72                 rc = opal_get_async_rc(msg);
  73                 if (rc != OPAL_SUCCESS) {
  74                         pr_debug("OPAL async call returned failed [rc=%d]\n",
  75                                 rc);
  76                         break;
  77                 }
  78         case OPAL_SUCCESS:
  79                 break;
  80         default:
  81                 pr_debug("OPAL write op-panel call failed [rc=%d]\n", rc);
  82         }
  83
  84         opal_async_release_token(token);
  85         return rc;
  86 }
  87
  88 static ssize_t oppanel_write(struct file *filp, const char __user *userbuf,
  89                              size_t len, loff_t *f_pos)
  90 {
  91         loff_t f_pos_prev = *f_pos;
  92         ssize_t ret;
  93         int rc;
  94
  95         if (!*f_pos)
  96                 memset(oppanel_data, ' ', oppanel_size);
  97         else if (*f_pos >= oppanel_size)
  98                 return -EFBIG;
  99
 100         ret = simple_write_to_buffer(oppanel_data, oppanel_size, f_pos, userbuf,
 101                         len);
 102         if (ret > 0) {
 103                 rc = __op_panel_update_display();
 104                 if (rc != OPAL_SUCCESS) {
 105                         pr_err_ratelimited("OPAL call failed to write to op panel display [rc=%d]\n",
 106                                 rc);
 107                         *f_pos = f_pos_prev;
 108                         return -EIO;
 109                 }
 110         }
 111         return ret;
 112 }
 113
 114 static int oppanel_open(struct inode *inode, struct file *filp)
 115 {
 116         if (!mutex_trylock(&oppanel_mutex)) {
 117                 pr_debug("Device Busy\n");
 118                 return -EBUSY;
 119         }
 120         return 0;
 121 }
 122
 123 static int oppanel_release(struct inode *inode, struct file *filp)
 124 {
 125         mutex_unlock(&oppanel_mutex);
 126         return 0;
 127 }
 128
 129 static const struct file_operations oppanel_fops = {
 130         .owner          = THIS_MODULE,
 131         .llseek         = oppanel_llseek,
 132         .read           = oppanel_read,
 133         .write          = oppanel_write,
 134         .open           = oppanel_open,
 135         .release        = oppanel_release
 136 };
 137
 138 static struct miscdevice oppanel_dev = {
 139         .minor          = MISC_DYNAMIC_MINOR,
 140         .name           = "op_panel",
 141         .fops           = &oppanel_fops
 142 };
 143
 144 static int oppanel_probe(struct platform_device *pdev)
 145 {
 146         struct device_node *np = pdev->dev.of_node;
 147         u32 line_len;
 148         int rc, i;
 149
 150         rc = of_property_read_u32(np, "#length", &line_len);
 151         if (rc) {
 152                 pr_err_ratelimited("Operator panel length property not found\n");
 153                 return rc;
 154         }
 155         rc = of_property_read_u32(np, "#lines", &num_lines);
 156         if (rc) {
 157                 pr_err_ratelimited("Operator panel lines property not found\n");
 158                 return rc;
 159         }
 160         oppanel_size = line_len * num_lines;
 161
 162         pr_devel("Operator panel of size %u found with %u lines of length %u\n",
 163                         oppanel_size, num_lines, line_len);
 164
 165         oppanel_data = kcalloc(oppanel_size, sizeof(*oppanel_data), GFP_KERNEL);
 166         if (!oppanel_data)
 167                 return -ENOMEM;
 168
 169         oppanel_lines = kcalloc(num_lines, sizeof(oppanel_line_t), GFP_KERNEL);
 170         if (!oppanel_lines) {
 171                 rc = -ENOMEM;
 172                 goto free_oppanel_data;
 173         }
 174
 175         memset(oppanel_data, ' ', oppanel_size);
 176         for (i = 0; i < num_lines; i++) {
 177                 oppanel_lines[i].line_len = cpu_to_be64(line_len);
 178                 oppanel_lines[i].line = cpu_to_be64(__pa(&oppanel_data[i *
 179                                                 line_len]));
 180         }
 181
 182         rc = misc_register(&oppanel_dev);
 183         if (rc) {
 184                 pr_err_ratelimited("Failed to register as misc device\n");
 185                 goto free_oppanel;
 186         }
 187
 188         return 0;
 189
 190 free_oppanel:
 191         kfree(oppanel_lines);
 192 free_oppanel_data:
 193         kfree(oppanel_data);
 194         return rc;
 195 }
 196
 197 static int oppanel_remove(struct platform_device *pdev)
 198 {
 199         misc_deregister(&oppanel_dev);
 200         kfree(oppanel_lines);
 201         kfree(oppanel_data);
 202         return 0;
 203 }
 204
 205 static const struct of_device_id oppanel_match[] = {
 206         { .compatible = "ibm,opal-oppanel" },
 207         { },
 208 };
 209
 210 static struct platform_driver oppanel_driver = {
 211         .driver = {
 212                 .name           = "powernv-op-panel",
 213                 .of_match_table = oppanel_match,
 214         },
 215         .probe  = oppanel_probe,
 216         .remove = oppanel_remove,
 217 };
 218
 219 module_platform_driver(oppanel_driver);
 220
 221 MODULE_DEVICE_TABLE(of, oppanel_match);
 222 MODULE_LICENSE("GPL v2");
 223 MODULE_DESCRIPTION("PowerNV Operator Panel LCD Display Driver");
 224 MODULE_AUTHOR("Suraj Jitindar Singh <sjitindarsingh@gmail.com>");