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                 break;
  79         case OPAL_SUCCESS:
  80                 break;
  81         default:
  82                 pr_debug("OPAL write op-panel call failed [rc=%d]\n", rc);
  83         }
  84
  85         opal_async_release_token(token);
  86         return rc;
  87 }
  88
  89 static ssize_t oppanel_write(struct file *filp, const char __user *userbuf,
  90                              size_t len, loff_t *f_pos)
  91 {
  92         loff_t f_pos_prev = *f_pos;
  93         ssize_t ret;
  94         int rc;
  95
  96         if (!*f_pos)
  97                 memset(oppanel_data, ' ', oppanel_size);
  98         else if (*f_pos >= oppanel_size)
  99                 return -EFBIG;
 100
 101         ret = simple_write_to_buffer(oppanel_data, oppanel_size, f_pos, userbuf,
 102                         len);
 103         if (ret > 0) {
 104                 rc = __op_panel_update_display();
 105                 if (rc != OPAL_SUCCESS) {
 106                         pr_err_ratelimited("OPAL call failed to write to op panel display [rc=%d]\n",
 107                                 rc);
 108                         *f_pos = f_pos_prev;
 109                         return -EIO;
 110                 }
 111         }
 112         return ret;
 113 }
 114
 115 static int oppanel_open(struct inode *inode, struct file *filp)
 116 {
 117         if (!mutex_trylock(&oppanel_mutex)) {
 118                 pr_debug("Device Busy\n");
 119                 return -EBUSY;
 120         }
 121         return 0;
 122 }
 123
 124 static int oppanel_release(struct inode *inode, struct file *filp)
 125 {
 126         mutex_unlock(&oppanel_mutex);
 127         return 0;
 128 }
 129
 130 static const struct file_operations oppanel_fops = {
 131         .owner          = THIS_MODULE,
 132         .llseek         = oppanel_llseek,
 133         .read           = oppanel_read,
 134         .write          = oppanel_write,
 135         .open           = oppanel_open,
 136         .release        = oppanel_release
 137 };
 138
 139 static struct miscdevice oppanel_dev = {
 140         .minor          = MISC_DYNAMIC_MINOR,
 141         .name           = "op_panel",
 142         .fops           = &oppanel_fops
 143 };
 144
 145 static int oppanel_probe(struct platform_device *pdev)
 146 {
 147         struct device_node *np = pdev->dev.of_node;
 148         u32 line_len;
 149         int rc, i;
 150
 151         rc = of_property_read_u32(np, "#length", &line_len);
 152         if (rc) {
 153                 pr_err_ratelimited("Operator panel length property not found\n");
 154                 return rc;
 155         }
 156         rc = of_property_read_u32(np, "#lines", &num_lines);
 157         if (rc) {
 158                 pr_err_ratelimited("Operator panel lines property not found\n");
 159                 return rc;
 160         }
 161         oppanel_size = line_len * num_lines;
 162
 163         pr_devel("Operator panel of size %u found with %u lines of length %u\n",
 164                         oppanel_size, num_lines, line_len);
 165
 166         oppanel_data = kcalloc(oppanel_size, sizeof(*oppanel_data), GFP_KERNEL);
 167         if (!oppanel_data)
 168                 return -ENOMEM;
 169
 170         oppanel_lines = kcalloc(num_lines, sizeof(oppanel_line_t), GFP_KERNEL);
 171         if (!oppanel_lines) {
 172                 rc = -ENOMEM;
 173                 goto free_oppanel_data;
 174         }
 175
 176         memset(oppanel_data, ' ', oppanel_size);
 177         for (i = 0; i < num_lines; i++) {
 178                 oppanel_lines[i].line_len = cpu_to_be64(line_len);
 179                 oppanel_lines[i].line = cpu_to_be64(__pa(&oppanel_data[i *
 180                                                 line_len]));
 181         }
 182
 183         rc = misc_register(&oppanel_dev);
 184         if (rc) {
 185                 pr_err_ratelimited("Failed to register as misc device\n");
 186                 goto free_oppanel;
 187         }
 188
 189         return 0;
 190
 191 free_oppanel:
 192         kfree(oppanel_lines);
 193 free_oppanel_data:
 194         kfree(oppanel_data);
 195         return rc;
 196 }
 197
 198 static void oppanel_remove(struct platform_device *pdev)
 199 {
 200         misc_deregister(&oppanel_dev);
 201         kfree(oppanel_lines);
 202         kfree(oppanel_data);
 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_new = 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>");