rt2x00: Driver requiring firmware should select crc algo

The driver should select what CRC algorithm is required
when performing a checksum on the firmware.

rt61pci & rt73usb require crc-itu-t
rt2800pci & rt2800usb require crc-ccitt

Legacy 2800pci/usb driver uses crc-itu-t + bit order reversion,
but that is just inefficient especially since the end result is
the same as a different algorithm which is also available as library. ;)

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 32 insertions, 9 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2x00firmware.c b/drivers/net/wireless/rt2x00/rt2x00firmware.c
index 442ff8047dce..4f9fe56f4f2e 100644
--- a/drivers/net/wireless/rt2x00/rt2x00firmware.c
+++ b/drivers/net/wireless/rt2x00/rt2x00firmware.c
@@ -23,6 +23,7 @@
         Abstract: rt2x00 firmware loading routines.
  */
 
+#include <linux/crc-ccitt.h>
 #include <linux/crc-itu-t.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -37,7 +38,6 @@ static int rt2x00lib_request_firmware(struct rt2x00_dev *rt2x00dev)
         char *fw_name;
         int retval;
         u16 crc;
-        u16 tmp;
 
         /*
          * Read correct firmware from harddisk.
@@ -64,17 +64,37 @@ static int rt2x00lib_request_firmware(struct rt2x00_dev *rt2x00dev)
         }
 
         /*
-         * Validate the firmware using 16 bit CRC.
-         * The last 2 bytes of the firmware are the CRC
-         * so substract those 2 bytes from the CRC checksum,
-         * and set those 2 bytes to 0 when calculating CRC.
+         * Perform crc validation on the firmware.
+         * The last 2 bytes in the firmware array are the crc checksum itself,
+         * this means that we should never pass those 2 bytes to the crc
+         * algorithm.
          */
-        tmp = 0;
-        crc = crc_itu_t(0, fw->data, fw->size - 2);
-        crc = crc_itu_t(crc, (u8 *)&tmp, 2);
+        if (test_bit(DRIVER_REQUIRE_FIRMWARE_CRC_ITU_T, &rt2x00dev->flags)) {
+                /*
+                 * Use the crc itu-t algorithm.
+                 * Use 0 for the last 2 bytes to complete the checksum.
+                 */
+                crc = crc_itu_t(0, fw->data, fw->size - 2);
+                crc = crc_itu_t_byte(crc, 0);
+                crc = crc_itu_t_byte(crc, 0);
+        } else if (test_bit(DRIVER_REQUIRE_FIRMWARE_CCITT, &rt2x00dev->flags)) {
+                /*
+                 * Use the crc ccitt algorithm.
+                 * This will return the same value as the legacy driver which
+                 * used bit ordering reversion on the both the firmware bytes
+                 * before input input as well as on the final output.
+                 * Obviously using crc ccitt directly is much more efficient.
+                 */
+                crc = crc_ccitt(~0, fw->data, fw->size - 2);
+        } else {
+                ERROR(rt2x00dev, "No checksum algorithm selected "
+                      "for firmware validation.\n");
+                retval = -ENOENT;
+                goto exit;
+        }
 
         if (crc != (fw->data[fw->size - 2] << 8 | fw->data[fw->size - 1])) {
-                ERROR(rt2x00dev, "Firmware CRC error.\n");
+                ERROR(rt2x00dev, "Firmware checksum error.\n");
                 retval = -ENOENT;
                 goto exit;
         }
@@ -96,6 +116,9 @@ int rt2x00lib_load_firmware(struct rt2x00_dev *rt2x00dev)
 {
         int retval;
 
+        if (!test_bit(DRIVER_REQUIRE_FIRMWARE, &rt2x00dev->flags))
+                return 0;
+
         if (!rt2x00dev->fw) {
                 retval = rt2x00lib_request_firmware(rt2x00dev);
                 if (retval)