[PATCH] w1_ds2433: Added crc16 protection and read caching.

The changes to ds2433 to add CRC16 protection and read caching.

Signed-off-by: Ben Gardner <bgardner@wabtec.com>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 111 insertions, 6 deletions

diff --git a/drivers/w1/w1_ds2433.c b/drivers/w1/w1_ds2433.c
index 9ec9163a0a9..b7c24b34d27 100644
--- a/drivers/w1/w1_ds2433.c
+++ b/drivers/w1/w1_ds2433.c
@@ -3,9 +3,8 @@
  *
  * Copyright (c) 2005 Ben Gardner <bgardner@wabtec.com>
  *
- * This program is free software; you can redistribute it and/or modify
- * it under the smems of the GNU General Public License as published by
- * the Free Software Foundation; version 2 of the License.
+ * This source code is licensed under the GNU General Public License,
+ * Version 2. See the file COPYING for more details.
  */
 
 #include <linux/kernel.h>
@@ -14,6 +13,9 @@
 #include <linux/device.h>
 #include <linux/types.h>
 #include <linux/delay.h>
+#ifdef CONFIG_W1_F23_CRC
+#include <linux/crc16.h>
+#endif
 
 #include "w1.h"
 #include "w1_io.h"
@@ -25,18 +27,26 @@ MODULE_AUTHOR("Ben Gardner <bgardner@wabtec.com>");
 MODULE_DESCRIPTION("w1 family 23 driver for DS2433, 4kb EEPROM");
 
 #define W1_EEPROM_SIZE          512
+#define W1_PAGE_COUNT           16
 #define W1_PAGE_SIZE            32
 #define W1_PAGE_BITS            5
 #define W1_PAGE_MASK            0x1F
 
+#define W1_F23_TIME             300
+
 #define W1_F23_READ_EEPROM      0xF0
 #define W1_F23_WRITE_SCRATCH    0x0F
 #define W1_F23_READ_SCRATCH     0xAA
 #define W1_F23_COPY_SCRATCH     0x55
 
+struct w1_f23_data {
+        u8      memory[W1_EEPROM_SIZE];
+        u32     validcrc;
+};
+
 /**
  * Check the file size bounds and adjusts count as needed.
- * This may not be needed if the sysfs layer checks bounds.
+ * This would not be needed if the file size didn't reset to 0 after a write.
  */
 static inline size_t w1_f23_fix_count(loff_t off, size_t count, size_t size)
 {
@@ -49,10 +59,45 @@ static inline size_t w1_f23_fix_count(loff_t off, size_t count, size_t size)
         return count;
 }
 
-static ssize_t w1_f23_read_bin(struct kobject *kobj, char *buf, loff_t off, size_t count)
+#ifdef CONFIG_W1_F23_CRC
+static int w1_f23_refresh_block(struct w1_slave *sl, struct w1_f23_data *data,
+                                int block)
+{
+        u8      wrbuf[3];
+        int     off = block * W1_PAGE_SIZE;
+
+        if (data->validcrc & (1 << block))
+                return 0;
+
+        if (w1_reset_select_slave(sl)) {
+                data->validcrc = 0;
+                return -EIO;
+        }
+
+        wrbuf[0] = W1_F23_READ_EEPROM;
+        wrbuf[1] = off & 0xff;
+        wrbuf[2] = off >> 8;
+        w1_write_block(sl->master, wrbuf, 3);
+        w1_read_block(sl->master, &data->memory[off], W1_PAGE_SIZE);
+
+        /* cache the block if the CRC is valid */
+        if (crc16(CRC16_INIT, &data->memory[off], W1_PAGE_SIZE) == CRC16_VALID)
+                data->validcrc |= (1 << block);
+
+        return 0;
+}
+#endif  /* CONFIG_W1_F23_CRC */
+
+static ssize_t w1_f23_read_bin(struct kobject *kobj, char *buf, loff_t off,
+                               size_t count)
 {
         struct w1_slave *sl = kobj_to_w1_slave(kobj);
+#ifdef CONFIG_W1_F23_CRC
+        struct w1_f23_data *data = sl->family_data;
+        int i, min_page, max_page;
+#else
         u8 wrbuf[3];
+#endif
 
         if ((count = w1_f23_fix_count(off, count, W1_EEPROM_SIZE)) == 0)
                 return 0;
@@ -63,6 +108,20 @@ static ssize_t w1_f23_read_bin(struct kobject *kobj, char *buf, loff_t off, size
                 goto out_dec;
         }
 
+#ifdef CONFIG_W1_F23_CRC
+
+        min_page = (off >> W1_PAGE_BITS);
+        max_page = (off + count - 1) >> W1_PAGE_BITS;
+        for (i = min_page; i <= max_page; i++) {
+                if (w1_f23_refresh_block(sl, data, i)) {
+                        count = -EIO;
+                        goto out_up;
+                }
+        }
+        memcpy(buf, &data->memory[off], count);
+
+#else   /* CONFIG_W1_F23_CRC */
+
         /* read directly from the EEPROM */
         if (w1_reset_select_slave(sl)) {
                 count = -EIO;
@@ -75,6 +134,8 @@ static ssize_t w1_f23_read_bin(struct kobject *kobj, char *buf, loff_t off, size
         w1_write_block(sl->master, wrbuf, 3);
         w1_read_block(sl->master, buf, count);
 
+#endif  /* CONFIG_W1_F23_CRC */
+
 out_up:
         up(&sl->master->mutex);
 out_dec:
@@ -85,6 +146,8 @@ out_dec:
 
 /**
  * Writes to the scratchpad and reads it back for verification.
+ * Then copies the scratchpad to EEPROM.
+ * The data must be on one page.
  * The master must be locked.
  *
  * @param sl    The slave structure
@@ -148,6 +211,23 @@ static ssize_t w1_f23_write_bin(struct kobject *kobj, char *buf, loff_t off,
         if ((count = w1_f23_fix_count(off, count, W1_EEPROM_SIZE)) == 0)
                 return 0;
 
+#ifdef CONFIG_W1_F23_CRC
+        /* can only write full blocks in cached mode */
+        if ((off & W1_PAGE_MASK) || (count & W1_PAGE_MASK)) {
+                dev_err(&sl->dev, "invalid offset/count off=%d cnt=%d\n",
+                        (int)off, count);
+                return -EINVAL;
+        }
+
+        /* make sure the block CRCs are valid */
+        for (idx = 0; idx < count; idx += W1_PAGE_SIZE) {
+                if (crc16(CRC16_INIT, &buf[idx], W1_PAGE_SIZE) != CRC16_VALID) {
+                        dev_err(&sl->dev, "bad CRC at offset %d\n", (int)off);
+                        return -EINVAL;
+                }
+        }
+#endif  /* CONFIG_W1_F23_CRC */
+
         atomic_inc(&sl->refcnt);
         if (down_interruptible(&sl->master->mutex)) {
                 count = 0;
@@ -190,11 +270,36 @@ static struct bin_attribute w1_f23_bin_attr = {
 
 static int w1_f23_add_slave(struct w1_slave *sl)
 {
-        return sysfs_create_bin_file(&sl->dev.kobj, &w1_f23_bin_attr);
+        int err;
+#ifdef CONFIG_W1_F23_CRC
+        struct w1_f23_data *data;
+
+        data = kmalloc(sizeof(struct w1_f23_data), GFP_KERNEL);
+        if (!data)
+                return -ENOMEM;
+        memset(data, 0, sizeof(struct w1_f23_data));
+        sl->family_data = data;
+
+#endif  /* CONFIG_W1_F23_CRC */
+
+        err = sysfs_create_bin_file(&sl->dev.kobj, &w1_f23_bin_attr);
+
+#ifdef CONFIG_W1_F23_CRC
+        if (err)
+                kfree(data);
+#endif  /* CONFIG_W1_F23_CRC */
+
+        return err;
 }
 
 static void w1_f23_remove_slave(struct w1_slave *sl)
 {
+#ifdef CONFIG_W1_F23_CRC
+        if (sl->family_data) {
+                kfree(sl->family_data);
+                sl->family_data = NULL;
+        }
+#endif  /* CONFIG_W1_F23_CRC */
         sysfs_remove_bin_file(&sl->dev.kobj, &w1_f23_bin_attr);
 }