p54: improve eeprom parser

Like other vendors, p54* devices have a checksum for
the EEPROM descriptor data. This patch enhances the
parser code to generate and verify the data fields,
before initializing the radio-chip on the card.

Note:
	If you have to bootstrap an alternative EEPROM image
	for your device and you don't know how to generate a
	valid crc ccitt checksum, you should take a look at:
	http://git.kernel.org/?p=linux/kernel/git/chr/p54tools.git

	The "checksum" utility loads a binary p54 EEPROM blob
	(use the -f switch, to skip the check) and applies
	the correct crc automatically.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

2 files changed, 19 insertions, 3 deletions

diff --git a/drivers/net/wireless/p54/Kconfig b/drivers/net/wireless/p54/Kconfig
index b0342a520bf1..60a930e45a8b 100644
--- a/drivers/net/wireless/p54/Kconfig
+++ b/drivers/net/wireless/p54/Kconfig
@@ -2,6 +2,7 @@ config P54_COMMON
         tristate "Softmac Prism54 support"
         depends on MAC80211 && EXPERIMENTAL
         select FW_LOADER
+        select CRC_CCITT
         ---help---
           This is common code for isl38xx/stlc45xx based modules.
           This module does nothing by itself - the USB/PCI/SPI front-ends
diff --git a/drivers/net/wireless/p54/eeprom.c b/drivers/net/wireless/p54/eeprom.c
index d687cb7f2a59..32d3f99b0844 100644
--- a/drivers/net/wireless/p54/eeprom.c
+++ b/drivers/net/wireless/p54/eeprom.c
@@ -23,6 +23,7 @@
 #include <linux/slab.h>
 
 #include <net/mac80211.h>
+#include <linux/crc-ccitt.h>
 
 #include "p54.h"
 #include "eeprom.h"
@@ -540,6 +541,7 @@ int p54_parse_eeprom(struct ieee80211_hw *dev, void *eeprom, int len)
         int err;
         u8 *end = (u8 *)eeprom + len;
         u16 synth = 0;
+        u16 crc16 = ~0;
 
         wrap = (struct eeprom_pda_wrap *) eeprom;
         entry = (void *)wrap->data + le16_to_cpu(wrap->len);
@@ -655,16 +657,29 @@ int p54_parse_eeprom(struct ieee80211_hw *dev, void *eeprom, int len)
                         }
                         break;
                 case PDR_END:
-                        /* make it overrun */
-                        entry_len = len;
+                        crc16 = ~crc_ccitt(crc16, (u8 *) entry, sizeof(*entry));
+                        if (crc16 != le16_to_cpup((__le16 *)entry->data)) {
+                                wiphy_err(dev->wiphy, "eeprom failed checksum "
+                                         "test!\n");
+                                err = -ENOMSG;
+                                goto err;
+                        } else {
+                                goto good_eeprom;
+                        }
                         break;
                 default:
                         break;
                 }
 
-                entry = (void *)entry + (entry_len + 1)*2;
+                crc16 = crc_ccitt(crc16, (u8 *)entry, (entry_len + 1) * 2);
+                entry = (void *)entry + (entry_len + 1) * 2;
         }
 
+        wiphy_err(dev->wiphy, "unexpected end of eeprom data.\n");
+        err = -ENODATA;
+        goto err;
+
+good_eeprom:
         if (!synth || !priv->iq_autocal || !priv->output_limit ||
             !priv->curve_data) {
                 wiphy_err(dev->wiphy,