[PATCH] zd1211rw: consistent handling of ZD1211 specific rates

As pointed out by Daniel Drake, the zd1211rw driver used several
different rate values and names throughout the driver. He has
written a patch to change it and tweaked it after some pretty wild
ideas from my side. But the discussion helped me to understand the
problem better and I think I have nailed it down with this patch.

A zd-rate will consist from now on of a four-bit "pure" rate value
and a modulation type flag as used in the ZD1211 control set used
for packet transmission. This is consistent with the usage in the
zd_rates table. If possible these zd-rates should be used in the
code.

Signed-off-by: Ulrich Kunitz <kune@deine-taler.de>
Signed-off-by: Daniel Drake <dsd@gentoo.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

4 files changed, 126 insertions, 132 deletions

diff --git a/drivers/net/wireless/zd1211rw/zd_chip.c b/drivers/net/wireless/zd1211rw/zd_chip.c
index 7e3c0625129b..495904218b1b 100644
--- a/drivers/net/wireless/zd1211rw/zd_chip.c
+++ b/drivers/net/wireless/zd1211rw/zd_chip.c
@@ -1009,19 +1009,19 @@ int zd_chip_set_rts_cts_rate_locked(struct zd_chip *chip,
         u32 value = 0;
 
         /* Modulation bit */
-        if (ZD_CS_TYPE(rts_rate) == ZD_CS_OFDM)
+        if (ZD_MODULATION_TYPE(rts_rate) == ZD_OFDM)
                 rts_mod = ZD_RX_OFDM;
 
         dev_dbg_f(zd_chip_dev(chip), "rts_rate=%x preamble=%x\n",
                 rts_rate, preamble);
 
-        value |= rts_rate << RTSCTS_SH_RTS_RATE;
+        value |= ZD_PURE_RATE(rts_rate) << RTSCTS_SH_RTS_RATE;
         value |= rts_mod << RTSCTS_SH_RTS_MOD_TYPE;
         value |= preamble << RTSCTS_SH_RTS_PMB_TYPE;
         value |= preamble << RTSCTS_SH_CTS_PMB_TYPE;
 
         /* We always send 11M self-CTS messages, like the vendor driver. */
-        value |= ZD_CCK_RATE_11M << RTSCTS_SH_CTS_RATE;
+        value |= ZD_PURE_RATE(ZD_CCK_RATE_11M) << RTSCTS_SH_CTS_RATE;
         value |= ZD_RX_CCK << RTSCTS_SH_CTS_MOD_TYPE;
 
         return zd_iowrite32_locked(chip, value, CR_RTS_CTS_RATE);
@@ -1328,7 +1328,7 @@ int zd_chip_set_basic_rates_locked(struct zd_chip *chip, u16 cr_rates)
         return zd_iowrite32_locked(chip, cr_rates, CR_BASIC_RATE_TBL);
 }
 
-static int ofdm_qual_db(u8 status_quality, u8 rate, unsigned int size)
+static int ofdm_qual_db(u8 status_quality, u8 zd_rate, unsigned int size)
 {
         static const u16 constants[] = {
                 715, 655, 585, 540, 470, 410, 360, 315,
@@ -1342,7 +1342,7 @@ static int ofdm_qual_db(u8 status_quality, u8 rate, unsigned int size)
         /* It seems that their quality parameter is somehow per signal
          * and is now transferred per bit.
          */
-        switch (rate) {
+        switch (zd_rate) {
         case ZD_OFDM_RATE_6M:
         case ZD_OFDM_RATE_12M:
         case ZD_OFDM_RATE_24M:
@@ -1369,7 +1369,7 @@ static int ofdm_qual_db(u8 status_quality, u8 rate, unsigned int size)
                         break;
         }
 
-        switch (rate) {
+        switch (zd_rate) {
         case ZD_OFDM_RATE_6M:
         case ZD_OFDM_RATE_9M:
                 i += 3;
@@ -1393,11 +1393,11 @@ static int ofdm_qual_db(u8 status_quality, u8 rate, unsigned int size)
         return i;
 }
 
-static int ofdm_qual_percent(u8 status_quality, u8 rate, unsigned int size)
+static int ofdm_qual_percent(u8 status_quality, u8 zd_rate, unsigned int size)
 {
         int r;
 
-        r = ofdm_qual_db(status_quality, rate, size);
+        r = ofdm_qual_db(status_quality, zd_rate, size);
         ZD_ASSERT(r >= 0);
         if (r < 0)
                 r = 0;
@@ -1458,12 +1458,17 @@ static int cck_qual_percent(u8 status_quality)
         return r <= 100 ? r : 100;
 }
 
+static inline u8 zd_rate_from_ofdm_plcp_header(const void *rx_frame)
+{
+        return ZD_OFDM | zd_ofdm_plcp_header_rate(rx_frame);
+}
+
 u8 zd_rx_qual_percent(const void *rx_frame, unsigned int size,
                       const struct rx_status *status)
 {
         return (status->frame_status&ZD_RX_OFDM) ?
                 ofdm_qual_percent(status->signal_quality_ofdm,
-                                  zd_ofdm_plcp_header_rate(rx_frame),
+                                          zd_rate_from_ofdm_plcp_header(rx_frame),
                                   size) :
                 cck_qual_percent(status->signal_quality_cck);
 }
@@ -1479,32 +1484,32 @@ u8 zd_rx_strength_percent(u8 rssi)
 u16 zd_rx_rate(const void *rx_frame, const struct rx_status *status)
 {
         static const u16 ofdm_rates[] = {
-                [ZD_OFDM_RATE_6M]  = 60,
-                [ZD_OFDM_RATE_9M]  = 90,
-                [ZD_OFDM_RATE_12M] = 120,
-                [ZD_OFDM_RATE_18M] = 180,
-                [ZD_OFDM_RATE_24M] = 240,
-                [ZD_OFDM_RATE_36M] = 360,
-                [ZD_OFDM_RATE_48M] = 480,
-                [ZD_OFDM_RATE_54M] = 540,
+                [ZD_OFDM_PLCP_RATE_6M]  = 60,
+                [ZD_OFDM_PLCP_RATE_9M]  = 90,
+                [ZD_OFDM_PLCP_RATE_12M] = 120,
+                [ZD_OFDM_PLCP_RATE_18M] = 180,
+                [ZD_OFDM_PLCP_RATE_24M] = 240,
+                [ZD_OFDM_PLCP_RATE_36M] = 360,
+                [ZD_OFDM_PLCP_RATE_48M] = 480,
+                [ZD_OFDM_PLCP_RATE_54M] = 540,
         };
         u16 rate;
         if (status->frame_status & ZD_RX_OFDM) {
+                /* Deals with PLCP OFDM rate (not zd_rates) */
                 u8 ofdm_rate = zd_ofdm_plcp_header_rate(rx_frame);
                 rate = ofdm_rates[ofdm_rate & 0xf];
         } else {
-                u8 cck_rate = zd_cck_plcp_header_rate(rx_frame);
-                switch (cck_rate) {
-                case ZD_CCK_SIGNAL_1M:
+                switch (zd_cck_plcp_header_signal(rx_frame)) {
+                case ZD_CCK_PLCP_SIGNAL_1M:
                         rate = 10;
                         break;
-                case ZD_CCK_SIGNAL_2M:
+                case ZD_CCK_PLCP_SIGNAL_2M:
                         rate = 20;
                         break;
-                case ZD_CCK_SIGNAL_5M5:
+                case ZD_CCK_PLCP_SIGNAL_5M5:
                         rate = 55;
                         break;
-                case ZD_CCK_SIGNAL_11M:
+                case ZD_CCK_PLCP_SIGNAL_11M:
                         rate = 110;
                         break;
                 default:
diff --git a/drivers/net/wireless/zd1211rw/zd_ieee80211.h b/drivers/net/wireless/zd1211rw/zd_ieee80211.h
index c4f36d39642b..fbf6491dce7e 100644
--- a/drivers/net/wireless/zd1211rw/zd_ieee80211.h
+++ b/drivers/net/wireless/zd1211rw/zd_ieee80211.h
@@ -43,21 +43,25 @@ struct ofdm_plcp_header {
         __le16 service;
 } __attribute__((packed));
 
-static inline u8 zd_ofdm_plcp_header_rate(
-        const struct ofdm_plcp_header *header)
+static inline u8 zd_ofdm_plcp_header_rate(const struct ofdm_plcp_header *header)
 {
         return header->prefix[0] & 0xf;
 }
 
-/* These are referred to as zd_rates */
-#define ZD_OFDM_RATE_6M         0xb
-#define ZD_OFDM_RATE_9M         0xf
-#define ZD_OFDM_RATE_12M        0xa
-#define ZD_OFDM_RATE_18M        0xe
-#define ZD_OFDM_RATE_24M        0x9
-#define ZD_OFDM_RATE_36M        0xd
-#define ZD_OFDM_RATE_48M        0x8
-#define ZD_OFDM_RATE_54M        0xc
+/* The following defines give the encoding of the 4-bit rate field in the
+ * OFDM (802.11a/802.11g) PLCP header. Notify that these values are used to
+ * define the zd-rate values for OFDM.
+ *
+ * See the struct zd_ctrlset definition in zd_mac.h.
+ */
+#define ZD_OFDM_PLCP_RATE_6M            0xb
+#define ZD_OFDM_PLCP_RATE_9M            0xf
+#define ZD_OFDM_PLCP_RATE_12M   0xa
+#define ZD_OFDM_PLCP_RATE_18M   0xe
+#define ZD_OFDM_PLCP_RATE_24M   0x9
+#define ZD_OFDM_PLCP_RATE_36M   0xd
+#define ZD_OFDM_PLCP_RATE_48M   0x8
+#define ZD_OFDM_PLCP_RATE_54M   0xc
 
 struct cck_plcp_header {
         u8 signal;
@@ -66,15 +70,22 @@ struct cck_plcp_header {
         __le16 crc16;
 } __attribute__((packed));
 
-static inline u8 zd_cck_plcp_header_rate(const struct cck_plcp_header *header)
+static inline u8 zd_cck_plcp_header_signal(const struct cck_plcp_header *header)
 {
         return header->signal;
 }
 
-#define ZD_CCK_SIGNAL_1M        0x0a
-#define ZD_CCK_SIGNAL_2M        0x14
-#define ZD_CCK_SIGNAL_5M5       0x37
-#define ZD_CCK_SIGNAL_11M       0x6e
+/* These defines give the encodings of the signal field in the 802.11b PLCP
+ * header. The signal field gives the bit rate of the following packet. Even
+ * if technically wrong we use CCK here also for the 1 MBit/s and 2 MBit/s
+ * rate to stay consistent with Zydas and our use of the term.
+ *
+ * Notify that these values are *not* used in the zd-rates.
+ */
+#define ZD_CCK_PLCP_SIGNAL_1M   0x0a
+#define ZD_CCK_PLCP_SIGNAL_2M   0x14
+#define ZD_CCK_PLCP_SIGNAL_5M5  0x37
+#define ZD_CCK_PLCP_SIGNAL_11M  0x6e
 
 enum ieee80211_std {
         IEEE80211B = 0x01,
diff --git a/drivers/net/wireless/zd1211rw/zd_mac.c b/drivers/net/wireless/zd1211rw/zd_mac.c
index 7ec1fcf37fc3..451308d7095d 100644
--- a/drivers/net/wireless/zd1211rw/zd_mac.c
+++ b/drivers/net/wireless/zd1211rw/zd_mac.c
@@ -610,28 +610,6 @@ u8 zd_mac_get_channel(struct zd_mac *mac)
         return channel;
 }
 
-/* If wrong rate is given, we are falling back to the slowest rate: 1MBit/s */
-static u8 zd_rate_typed(u8 zd_rate)
-{
-        static const u8 typed_rates[16] = {
-                [ZD_CCK_RATE_1M]        = ZD_CS_CCK|ZD_CCK_RATE_1M,
-                [ZD_CCK_RATE_2M]        = ZD_CS_CCK|ZD_CCK_RATE_2M,
-                [ZD_CCK_RATE_5_5M]      = ZD_CS_CCK|ZD_CCK_RATE_5_5M,
-                [ZD_CCK_RATE_11M]       = ZD_CS_CCK|ZD_CCK_RATE_11M,
-                [ZD_OFDM_RATE_6M]       = ZD_CS_OFDM|ZD_OFDM_RATE_6M,
-                [ZD_OFDM_RATE_9M]       = ZD_CS_OFDM|ZD_OFDM_RATE_9M,
-                [ZD_OFDM_RATE_12M]      = ZD_CS_OFDM|ZD_OFDM_RATE_12M,
-                [ZD_OFDM_RATE_18M]      = ZD_CS_OFDM|ZD_OFDM_RATE_18M,
-                [ZD_OFDM_RATE_24M]      = ZD_CS_OFDM|ZD_OFDM_RATE_24M,
-                [ZD_OFDM_RATE_36M]      = ZD_CS_OFDM|ZD_OFDM_RATE_36M,
-                [ZD_OFDM_RATE_48M]      = ZD_CS_OFDM|ZD_OFDM_RATE_48M,
-                [ZD_OFDM_RATE_54M]      = ZD_CS_OFDM|ZD_OFDM_RATE_54M,
-        };
-
-        ZD_ASSERT(ZD_CS_RATE_MASK == 0x0f);
-        return typed_rates[zd_rate & ZD_CS_RATE_MASK];
-}
-
 int zd_mac_set_mode(struct zd_mac *mac, u32 mode)
 {
         struct ieee80211_device *ieee;
@@ -739,25 +717,30 @@ int zd_mac_get_range(struct zd_mac *mac, struct iw_range *range)
 
 static int zd_calc_tx_length_us(u8 *service, u8 zd_rate, u16 tx_length)
 {
+        /* ZD_PURE_RATE() must be used to remove the modulation type flag of
+         * the zd-rate values. */
         static const u8 rate_divisor[] = {
-                [ZD_CCK_RATE_1M]        =  1,
-                [ZD_CCK_RATE_2M]        =  2,
-                [ZD_CCK_RATE_5_5M]      = 11, /* bits must be doubled */
-                [ZD_CCK_RATE_11M]       = 11,
-                [ZD_OFDM_RATE_6M]       =  6,
-                [ZD_OFDM_RATE_9M]       =  9,
-                [ZD_OFDM_RATE_12M]      = 12,
-                [ZD_OFDM_RATE_18M]      = 18,
-                [ZD_OFDM_RATE_24M]      = 24,
-                [ZD_OFDM_RATE_36M]      = 36,
-                [ZD_OFDM_RATE_48M]      = 48,
-                [ZD_OFDM_RATE_54M]      = 54,
+                [ZD_PURE_RATE(ZD_CCK_RATE_1M)]          =  1,
+                [ZD_PURE_RATE(ZD_CCK_RATE_2M)]          =  2,
+
+                /* bits must be doubled */
+                [ZD_PURE_RATE(ZD_CCK_RATE_5_5M)]        = 11,
+
+                [ZD_PURE_RATE(ZD_CCK_RATE_11M)]         = 11,
+                [ZD_PURE_RATE(ZD_OFDM_RATE_6M)]         =  6,
+                [ZD_PURE_RATE(ZD_OFDM_RATE_9M)]         =  9,
+                [ZD_PURE_RATE(ZD_OFDM_RATE_12M)]        = 12,
+                [ZD_PURE_RATE(ZD_OFDM_RATE_18M)]        = 18,
+                [ZD_PURE_RATE(ZD_OFDM_RATE_24M)]        = 24,
+                [ZD_PURE_RATE(ZD_OFDM_RATE_36M)]        = 36,
+                [ZD_PURE_RATE(ZD_OFDM_RATE_48M)]        = 48,
+                [ZD_PURE_RATE(ZD_OFDM_RATE_54M)]        = 54,
         };
 
         u32 bits = (u32)tx_length * 8;
         u32 divisor;
 
-        divisor = rate_divisor[zd_rate];
+        divisor = rate_divisor[ZD_PURE_RATE(zd_rate)];
         if (divisor == 0)
                 return -EINVAL;
 
@@ -780,52 +763,24 @@ static int zd_calc_tx_length_us(u8 *service, u8 zd_rate, u16 tx_length)
         return bits/divisor;
 }
 
-enum {
-        R2M_SHORT_PREAMBLE = 0x01,
-        R2M_11A            = 0x02,
-};
-
-static u8 zd_rate_to_modulation(u8 zd_rate, int flags)
-{
-        u8 modulation;
-
-        modulation = zd_rate_typed(zd_rate);
-        if (flags & R2M_SHORT_PREAMBLE) {
-                switch (ZD_CS_RATE(modulation)) {
-                case ZD_CCK_RATE_2M:
-                case ZD_CCK_RATE_5_5M:
-                case ZD_CCK_RATE_11M:
-                        modulation |= ZD_CS_CCK_PREA_SHORT;
-                        return modulation;
-                }
-        }
-        if (flags & R2M_11A) {
-                if (ZD_CS_TYPE(modulation) == ZD_CS_OFDM)
-                        modulation |= ZD_CS_OFDM_MODE_11A;
-        }
-        return modulation;
-}
-
 static void cs_set_modulation(struct zd_mac *mac, struct zd_ctrlset *cs,
                               struct ieee80211_hdr_4addr *hdr)
 {
         struct ieee80211softmac_device *softmac = ieee80211_priv(mac->netdev);
         u16 ftype = WLAN_FC_GET_TYPE(le16_to_cpu(hdr->frame_ctl));
-        u8 rate, zd_rate;
+        u8 rate;
         int is_mgt = (ftype == IEEE80211_FTYPE_MGMT) != 0;
         int is_multicast = is_multicast_ether_addr(hdr->addr1);
         int short_preamble = ieee80211softmac_short_preamble_ok(softmac,
                 is_multicast, is_mgt);
-        int flags = 0;
 
-        /* FIXME: 802.11a? */
         rate = ieee80211softmac_suggest_txrate(softmac, is_multicast, is_mgt);
+        cs->modulation = rate_to_zd_rate(rate);
 
-        if (short_preamble)
-                flags |= R2M_SHORT_PREAMBLE;
-
-        zd_rate = rate_to_zd_rate(rate);
-        cs->modulation = zd_rate_to_modulation(zd_rate, flags);
+        /* Set short preamble bit when appropriate */
+        if (short_preamble && ZD_MODULATION_TYPE(cs->modulation) == ZD_CCK
+            && cs->modulation != ZD_CCK_RATE_1M)
+                cs->modulation |= ZD_CCK_PREA_SHORT;
 }
 
 static void cs_set_control(struct zd_mac *mac, struct zd_ctrlset *cs,
@@ -864,7 +819,7 @@ static void cs_set_control(struct zd_mac *mac, struct zd_ctrlset *cs,
                 cs->control |= ZD_CS_RTS;
 
         /* Use CTS-to-self protection if required */
-        if (ZD_CS_TYPE(cs->modulation) == ZD_CS_OFDM &&
+        if (ZD_MODULATION_TYPE(cs->modulation) == ZD_OFDM &&
                         ieee80211softmac_protection_needed(softmac)) {
                 /* FIXME: avoid sending RTS *and* self-CTS, is that correct? */
                 cs->control &= ~ZD_CS_RTS;
@@ -925,7 +880,7 @@ static int fill_ctrlset(struct zd_mac *mac,
          * - see line 53 of zdinlinef.h
          */
         cs->service = 0;
-        r = zd_calc_tx_length_us(&cs->service, ZD_CS_RATE(cs->modulation),
+        r = zd_calc_tx_length_us(&cs->service, ZD_RATE(cs->modulation),
                                  le16_to_cpu(cs->tx_length));
         if (r < 0)
                 return r;
@@ -934,7 +889,7 @@ static int fill_ctrlset(struct zd_mac *mac,
         if (next_frag_len == 0) {
                 cs->next_frame_length = 0;
         } else {
-                r = zd_calc_tx_length_us(NULL, ZD_CS_RATE(cs->modulation),
+                r = zd_calc_tx_length_us(NULL, ZD_RATE(cs->modulation),
                                          next_frag_len);
                 if (r < 0)
                         return r;
diff --git a/drivers/net/wireless/zd1211rw/zd_mac.h b/drivers/net/wireless/zd1211rw/zd_mac.h
index 9f9344eb50f9..1b15bde3ff60 100644
--- a/drivers/net/wireless/zd1211rw/zd_mac.h
+++ b/drivers/net/wireless/zd1211rw/zd_mac.h
@@ -40,28 +40,51 @@ struct zd_ctrlset {
 
 #define ZD_CS_RESERVED_SIZE     25
 
-/* zd_crtlset field modulation */
-#define ZD_CS_RATE_MASK         0x0f
-#define ZD_CS_TYPE_MASK         0x10
-#define ZD_CS_RATE(modulation) ((modulation) & ZD_CS_RATE_MASK)
-#define ZD_CS_TYPE(modulation) ((modulation) & ZD_CS_TYPE_MASK)
-
-#define ZD_CS_CCK               0x00
-#define ZD_CS_OFDM              0x10
-
-/* These are referred to as zd_rates */
-#define ZD_CCK_RATE_1M  0x00
-#define ZD_CCK_RATE_2M  0x01
-#define ZD_CCK_RATE_5_5M        0x02
-#define ZD_CCK_RATE_11M 0x03
-/* The rates for OFDM are encoded as in the PLCP header. Use ZD_OFDM_RATE_*.
+/* The field modulation of struct zd_ctrlset controls the bit rate, the use
+ * of short or long preambles in 802.11b (CCK mode) or the use of 802.11a or
+ * 802.11g in OFDM mode.
+ *
+ * The term zd-rate is used for the combination of the modulation type flag
+ * and the "pure" rate value.
  */
-
-/* bit 5 is preamble (when in CCK mode), or a/g selection (when in OFDM mode) */
-#define ZD_CS_CCK_PREA_LONG     0x00
-#define ZD_CS_CCK_PREA_SHORT    0x20
-#define ZD_CS_OFDM_MODE_11G     0x00
-#define ZD_CS_OFDM_MODE_11A     0x20
+#define ZD_PURE_RATE_MASK       0x0f
+#define ZD_MODULATION_TYPE_MASK 0x10
+#define ZD_RATE_MASK            (ZD_PURE_RATE_MASK|ZD_MODULATION_TYPE_MASK)
+#define ZD_PURE_RATE(modulation) ((modulation) & ZD_PURE_RATE_MASK)
+#define ZD_MODULATION_TYPE(modulation) ((modulation) & ZD_MODULATION_TYPE_MASK)
+#define ZD_RATE(modulation) ((modulation) & ZD_RATE_MASK)
+
+/* The two possible modulation types. Notify that 802.11b doesn't use the CCK
+ * codeing for the 1 and 2 MBit/s rate. We stay with the term here to remain
+ * consistent with uses the term at other places.
+  */
+#define ZD_CCK                  0x00
+#define ZD_OFDM                 0x10
+
+/* The ZD1211 firmware uses proprietary encodings of the 802.11b (CCK) rates.
+ * For OFDM the PLCP rate encodings are used. We combine these "pure" rates
+ * with the modulation type flag and call the resulting values zd-rates.
+ */
+#define ZD_CCK_RATE_1M          (ZD_CCK|0x00)
+#define ZD_CCK_RATE_2M          (ZD_CCK|0x01)
+#define ZD_CCK_RATE_5_5M        (ZD_CCK|0x02)
+#define ZD_CCK_RATE_11M         (ZD_CCK|0x03)
+#define ZD_OFDM_RATE_6M         (ZD_OFDM|ZD_OFDM_PLCP_RATE_6M)
+#define ZD_OFDM_RATE_9M         (ZD_OFDM|ZD_OFDM_PLCP_RATE_9M)
+#define ZD_OFDM_RATE_12M        (ZD_OFDM|ZD_OFDM_PLCP_RATE_12M)
+#define ZD_OFDM_RATE_18M        (ZD_OFDM|ZD_OFDM_PLCP_RATE_18M)
+#define ZD_OFDM_RATE_24M        (ZD_OFDM|ZD_OFDM_PLCP_RATE_24M)
+#define ZD_OFDM_RATE_36M        (ZD_OFDM|ZD_OFDM_PLCP_RATE_36M)
+#define ZD_OFDM_RATE_48M        (ZD_OFDM|ZD_OFDM_PLCP_RATE_48M)
+#define ZD_OFDM_RATE_54M        (ZD_OFDM|ZD_OFDM_PLCP_RATE_54M)
+
+/* The bit 5 of the zd_ctrlset modulation field controls the preamble in CCK
+ * mode or the 802.11a/802.11g selection in OFDM mode.
+ */
+#define ZD_CCK_PREA_LONG        0x00
+#define ZD_CCK_PREA_SHORT       0x20
+#define ZD_OFDM_MODE_11G        0x00
+#define ZD_OFDM_MODE_11A        0x20
 
 /* zd_ctrlset control field */
 #define ZD_CS_NEED_RANDOM_BACKOFF       0x01