2010-08-16 23:17:02

by Christian Lamparter

Subject: [PATCH 2/2] 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 <[email protected]>
---
diff --git a/drivers/net/wireless/p54/Kconfig b/drivers/net/wireless/p54/Kconfig
index b0342a5..60a930e 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 d687cb7..32d3f99 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,

2010-08-16 23:51:45

by Larry Finger

Subject: Re: [PATCH 2/2] p54: improve eeprom parser

On 08/16/2010 06:16 PM, Christian Lamparter wrote:
> 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 <[email protected]>

ACK for p54usb.

Larry