iwlwifi: add comments to EEPROM stuff

Add comments to EEPROM stuff.

Signed-off-by: Ben Cahill <ben.m.cahill@intel.com>
Signed-off-by: Zhu Yi <yi.zhu@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

4 files changed, 285 insertions, 36 deletions

diff --git a/drivers/net/wireless/iwlwifi/iwl-3945-hw.h b/drivers/net/wireless/iwlwifi/iwl-3945-hw.h
index 8bbaa16442a..2c9f884be03 100644
--- a/drivers/net/wireless/iwlwifi/iwl-3945-hw.h
+++ b/drivers/net/wireless/iwlwifi/iwl-3945-hw.h
@@ -85,24 +85,48 @@
 #define IWL_RSSI_OFFSET 95
 
 /*
- * This file defines EEPROM related constants, enums, and inline functions.
- *
+ * EEPROM related constants, enums, and structures.
  */
 
+/*
+ * EEPROM access time values:
+ *
+ * Driver initiates EEPROM read by writing byte address << 1 to CSR_EEPROM_REG,
+ *   then clearing (with subsequent read/modify/write) CSR_EEPROM_REG bit
+ *   CSR_EEPROM_REG_BIT_CMD (0x2).
+ * Driver then polls CSR_EEPROM_REG for CSR_EEPROM_REG_READ_VALID_MSK (0x1).
+ * When polling, wait 10 uSec between polling loops, up to a maximum 5000 uSec.
+ * Driver reads 16-bit value from bits 31-16 of CSR_EEPROM_REG.
+ */
 #define IWL_EEPROM_ACCESS_TIMEOUT       5000 /* uSec */
 #define IWL_EEPROM_ACCESS_DELAY         10   /* uSec */
+
 /* EEPROM field values */
 #define ANTENNA_SWITCH_NORMAL     0
 #define ANTENNA_SWITCH_INVERSE    1
 
+/*
+ * Regulatory channel usage flags in EEPROM struct iwl_eeprom_channel.flags.
+ *
+ * IBSS and/or AP operation is allowed *only* on those channels with
+ * (VALID && IBSS && ACTIVE && !RADAR).  This restriction is in place because
+ * RADAR detection is not supported by the 3945 driver, but is a
+ * requirement for establishing a new network for legal operation on channels
+ * requiring RADAR detection or restricting ACTIVE scanning.
+ *
+ * NOTE:  "WIDE" flag indicates that 20 MHz channel is supported;
+ *        3945 does not support FAT 40 MHz-wide channels.
+ *
+ * NOTE:  Using a channel inappropriately will result in a uCode error!
+ */
 enum {
         EEPROM_CHANNEL_VALID = (1 << 0),        /* usable for this SKU/geo */
-        EEPROM_CHANNEL_IBSS = (1 << 1), /* usable as an IBSS channel */
+        EEPROM_CHANNEL_IBSS = (1 << 1),         /* usable as an IBSS channel */
         /* Bit 2 Reserved */
         EEPROM_CHANNEL_ACTIVE = (1 << 3),       /* active scanning allowed */
         EEPROM_CHANNEL_RADAR = (1 << 4),        /* radar detection required */
-        EEPROM_CHANNEL_WIDE = (1 << 5),
-        EEPROM_CHANNEL_NARROW = (1 << 6),
+        EEPROM_CHANNEL_WIDE = (1 << 5),         /* 20 MHz channel okay */
+        EEPROM_CHANNEL_NARROW = (1 << 6),       /* 10 MHz channel, not used */
         EEPROM_CHANNEL_DFS = (1 << 7),  /* dynamic freq selection candidate */
 };
 
@@ -147,6 +171,7 @@ struct iwl3945_eeprom_channel {
  *   long packets in normal operation to provide feedback as to proper output
  *   level.
  * Data copied from EEPROM.
+ * DO NOT ALTER THIS STRUCTURE!!!
  */
 struct iwl3945_eeprom_txpower_sample {
         u8 gain_index;          /* index into power (gain) setup table ... */
@@ -163,11 +188,11 @@ struct iwl3945_eeprom_txpower_sample {
  * DO NOT ALTER THIS STRUCTURE!!!
  */
 struct iwl3945_eeprom_txpower_group {
-        struct iwl3945_eeprom_txpower_sample samples[5];        /* 5 power levels */
+        struct iwl3945_eeprom_txpower_sample samples[5];  /* 5 power levels */
         s32 a, b, c, d, e;      /* coefficients for voltage->power
                                  * formula (signed) */
         s32 Fa, Fb, Fc, Fd, Fe; /* these modify coeffs based on
-                                         * frequency (signed) */
+                                 * frequency (signed) */
         s8 saturation_power;    /* highest power possible by h/w in this
                                  * band */
         u8 group_channel;       /* "representative" channel # in this band */
@@ -189,6 +214,9 @@ struct iwl3945_eeprom_temperature_corr {
         u32 Te;
 } __attribute__ ((packed));
 
+/*
+ * EEPROM map
+ */
 struct iwl3945_eeprom {
         u8 reserved0[16];
 #define EEPROM_DEVICE_ID                    (2*0x08)    /* 2 bytes */
@@ -229,29 +257,67 @@ struct iwl3945_eeprom {
         u8 reserved6[42];
 #define EEPROM_REGULATORY_SKU_ID            (2*0x60)    /* 4  bytes */
         u8 sku_id[4];           /* abs.ofs: 192 */
+
+/*
+ * Per-channel regulatory data.
+ *
+ * Each channel that *might* be supported by 3945 or 4965 has a fixed location
+ * in EEPROM containing EEPROM_CHANNEL_* usage flags (LSB) and max regulatory
+ * txpower (MSB).
+ *
+ * Entries immediately below are for 20 MHz channel width.  FAT (40 MHz)
+ * channels (only for 4965, not supported by 3945) appear later in the EEPROM.
+ *
+ * 2.4 GHz channels 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
+ */
 #define EEPROM_REGULATORY_BAND_1            (2*0x62)    /* 2  bytes */
         u16 band_1_count;       /* abs.ofs: 196 */
 #define EEPROM_REGULATORY_BAND_1_CHANNELS   (2*0x63)    /* 28 bytes */
-        struct iwl3945_eeprom_channel band_1_channels[14];      /* abs.ofs: 196 */
+        struct iwl3945_eeprom_channel band_1_channels[14];  /* abs.ofs: 196 */
+
+/*
+ * 4.9 GHz channels 183, 184, 185, 187, 188, 189, 192, 196,
+ * 5.0 GHz channels 7, 8, 11, 12, 16
+ * (4915-5080MHz) (none of these is ever supported)
+ */
 #define EEPROM_REGULATORY_BAND_2            (2*0x71)    /* 2  bytes */
         u16 band_2_count;       /* abs.ofs: 226 */
 #define EEPROM_REGULATORY_BAND_2_CHANNELS   (2*0x72)    /* 26 bytes */
-        struct iwl3945_eeprom_channel band_2_channels[13];      /* abs.ofs: 228 */
+        struct iwl3945_eeprom_channel band_2_channels[13];  /* abs.ofs: 228 */
+
+/*
+ * 5.2 GHz channels 34, 36, 38, 40, 42, 44, 46, 48, 52, 56, 60, 64
+ * (5170-5320MHz)
+ */
 #define EEPROM_REGULATORY_BAND_3            (2*0x7F)    /* 2  bytes */
         u16 band_3_count;       /* abs.ofs: 254 */
 #define EEPROM_REGULATORY_BAND_3_CHANNELS   (2*0x80)    /* 24 bytes */
-        struct iwl3945_eeprom_channel band_3_channels[12];      /* abs.ofs: 256 */
+        struct iwl3945_eeprom_channel band_3_channels[12];  /* abs.ofs: 256 */
+
+/*
+ * 5.5 GHz channels 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140
+ * (5500-5700MHz)
+ */
 #define EEPROM_REGULATORY_BAND_4            (2*0x8C)    /* 2  bytes */
         u16 band_4_count;       /* abs.ofs: 280 */
 #define EEPROM_REGULATORY_BAND_4_CHANNELS   (2*0x8D)    /* 22 bytes */
-        struct iwl3945_eeprom_channel band_4_channels[11];      /* abs.ofs: 282 */
+        struct iwl3945_eeprom_channel band_4_channels[11];  /* abs.ofs: 282 */
+
+/*
+ * 5.7 GHz channels 145, 149, 153, 157, 161, 165
+ * (5725-5825MHz)
+ */
 #define EEPROM_REGULATORY_BAND_5            (2*0x98)    /* 2  bytes */
         u16 band_5_count;       /* abs.ofs: 304 */
 #define EEPROM_REGULATORY_BAND_5_CHANNELS   (2*0x99)    /* 12 bytes */
-        struct iwl3945_eeprom_channel band_5_channels[6];       /* abs.ofs: 306 */
+        struct iwl3945_eeprom_channel band_5_channels[6];  /* abs.ofs: 306 */
 
         u8 reserved9[194];
 
+
+/*
+ * 3945 Txpower calibration data.
+ */
 #define EEPROM_TXPOWER_CALIB_GROUP0 0x200
 #define EEPROM_TXPOWER_CALIB_GROUP1 0x240
 #define EEPROM_TXPOWER_CALIB_GROUP2 0x280
@@ -261,12 +327,14 @@ struct iwl3945_eeprom {
         struct iwl3945_eeprom_txpower_group groups[IWL_NUM_TX_CALIB_GROUPS];
 /* abs.ofs: 512 */
 #define EEPROM_CALIB_TEMPERATURE_CORRECT 0x340
-        struct iwl3945_eeprom_temperature_corr corrections;     /* abs.ofs: 832 */
+        struct iwl3945_eeprom_temperature_corr corrections;  /* abs.ofs: 832 */
         u8 reserved16[172];     /* fill out to full 1024 byte block */
 } __attribute__ ((packed));
 
 #define IWL_EEPROM_IMAGE_SIZE 1024
 
+/* End of EEPROM */
+
 
 #include "iwl-3945-commands.h"
 
diff --git a/drivers/net/wireless/iwlwifi/iwl-3945.c b/drivers/net/wireless/iwlwifi/iwl-3945.c
index 953a9bec063..51b90309ce5 100644
--- a/drivers/net/wireless/iwlwifi/iwl-3945.c
+++ b/drivers/net/wireless/iwlwifi/iwl-3945.c
@@ -2202,6 +2202,7 @@ int iwl3945_init_hw_rate_table(struct iwl3945_priv *priv)
                                 &rate_cmd);
 }
 
+/* Called when initializing driver */
 int iwl3945_hw_set_hw_setting(struct iwl3945_priv *priv)
 {
         memset((void *)&priv->hw_setting, 0,
@@ -2284,6 +2285,14 @@ struct pci_device_id iwl3945_hw_card_ids[] = {
         {0}
 };
 
+/*
+ * Clear the OWNER_MSK, to establish driver (instead of uCode running on
+ * embedded controller) as EEPROM reader; each read is a series of pulses
+ * to/from the EEPROM chip, not a single event, so even reads could conflict
+ * if they weren't arbitrated by some ownership mechanism.  Here, the driver
+ * simply claims ownership, which should be safe when this function is called
+ * (i.e. before loading uCode!).
+ */
 inline int iwl3945_eeprom_acquire_semaphore(struct iwl3945_priv *priv)
 {
         _iwl3945_clear_bit(priv, CSR_EEPROM_GP, CSR_EEPROM_GP_IF_OWNER_MSK);
diff --git a/drivers/net/wireless/iwlwifi/iwl-4965-hw.h b/drivers/net/wireless/iwlwifi/iwl-4965-hw.h
index dfaa6077946..4741fa22831 100644
--- a/drivers/net/wireless/iwlwifi/iwl-4965-hw.h
+++ b/drivers/net/wireless/iwlwifi/iwl-4965-hw.h
@@ -85,24 +85,50 @@
 #define IWL_RSSI_OFFSET 44
 
 /*
- * This file defines EEPROM related constants, enums, and inline functions.
- *
+ * EEPROM related constants, enums, and structures.
  */
 
+/*
+ * EEPROM access time values:
+ *
+ * Driver initiates EEPROM read by writing byte address << 1 to CSR_EEPROM_REG,
+ *   then clearing (with subsequent read/modify/write) CSR_EEPROM_REG bit
+ *   CSR_EEPROM_REG_BIT_CMD (0x2).
+ * Driver then polls CSR_EEPROM_REG for CSR_EEPROM_REG_READ_VALID_MSK (0x1).
+ * When polling, wait 10 uSec between polling loops, up to a maximum 5000 uSec.
+ * Driver reads 16-bit value from bits 31-16 of CSR_EEPROM_REG.
+ */
 #define IWL_EEPROM_ACCESS_TIMEOUT       5000 /* uSec */
 #define IWL_EEPROM_ACCESS_DELAY         10   /* uSec */
+
 /* EEPROM field values */
 #define ANTENNA_SWITCH_NORMAL     0
 #define ANTENNA_SWITCH_INVERSE    1
 
+/*
+ * Regulatory channel usage flags in EEPROM struct iwl4965_eeprom_channel.flags.
+ *
+ * IBSS and/or AP operation is allowed *only* on those channels with
+ * (VALID && IBSS && ACTIVE && !RADAR).  This restriction is in place because
+ * RADAR detection is not supported by the 4965 driver, but is a
+ * requirement for establishing a new network for legal operation on channels
+ * requiring RADAR detection or restricting ACTIVE scanning.
+ *
+ * NOTE:  "WIDE" flag does not indicate anything about "FAT" 40 MHz channels.
+ *        It only indicates that 20 MHz channel use is supported; FAT channel
+ *        usage is indicated by a separate set of regulatory flags for each
+ *        FAT channel pair.
+ *
+ * NOTE:  Using a channel inappropriately will result in a uCode error!
+ */
 enum {
         EEPROM_CHANNEL_VALID = (1 << 0),        /* usable for this SKU/geo */
-        EEPROM_CHANNEL_IBSS = (1 << 1), /* usable as an IBSS channel */
+        EEPROM_CHANNEL_IBSS = (1 << 1),         /* usable as an IBSS channel */
         /* Bit 2 Reserved */
         EEPROM_CHANNEL_ACTIVE = (1 << 3),       /* active scanning allowed */
         EEPROM_CHANNEL_RADAR = (1 << 4),        /* radar detection required */
-        EEPROM_CHANNEL_WIDE = (1 << 5),
-        EEPROM_CHANNEL_NARROW = (1 << 6),
+        EEPROM_CHANNEL_WIDE = (1 << 5),         /* 20 MHz channel okay */
+        EEPROM_CHANNEL_NARROW = (1 << 6),       /* 10 MHz channel, not used */
         EEPROM_CHANNEL_DFS = (1 << 7),  /* dynamic freq selection candidate */
 };
 
@@ -136,9 +162,10 @@ enum {
 #define EEPROM_SKU_CAP_HW_RF_KILL_ENABLE                (1 << 1)
 #define EEPROM_SKU_CAP_OP_MODE_MRC                      (1 << 7)
 
-/* *regulatory* channel data from eeprom, one for each channel */
+/* *regulatory* channel data format in eeprom, one for each channel.
+ * There are separate entries for FAT (40 MHz) vs. normal (20 MHz) channels. */
 struct iwl4965_eeprom_channel {
-        u8 flags;               /* flags copied from EEPROM */
+        u8 flags;               /* EEPROM_CHANNEL_* flags copied from EEPROM */
         s8 max_power_avg;       /* max power (dBm) on this chnl, limit 31 */
 } __attribute__ ((packed));
 
@@ -193,44 +220,112 @@ struct iwl4965_eeprom_temperature_corr {
         u32 Te;
 } __attribute__ ((packed));
 
+/* 4965 has two radio transmitters (and 3 radio receivers) */
 #define EEPROM_TX_POWER_TX_CHAINS      (2)
+
+/* 4965 has room for up to 8 sets of txpower calibration data */
 #define EEPROM_TX_POWER_BANDS          (8)
+
+/* 4965 factory calibration measures txpower gain settings for
+ * each of 3 target output levels */
 #define EEPROM_TX_POWER_MEASUREMENTS   (3)
+
 #define EEPROM_TX_POWER_VERSION        (2)
+
+/* 4965 driver does not work with txpower calibration version < 5.
+ * Look for this in calib_version member of struct iwl4965_eeprom. */
 #define EEPROM_TX_POWER_VERSION_NEW    (5)
 
+
+/*
+ * 4965 factory calibration data for one txpower level, on one channel,
+ * measured on one of the 2 tx chains (radio transmitter and associated
+ * antenna).  EEPROM contains:
+ *
+ * 1)  Temperature (degrees Celsius) of device when measurement was made.
+ *
+ * 2)  Gain table index used to achieve the target measurement power.
+ *     This refers to the "well-known" gain tables (see iwl-4965-hw.h).
+ *
+ * 3)  Actual measured output power, in half-dBm ("34" = 17 dBm).
+ *
+ * 4)  RF power amplifier detector level measurement (not used).
+ */
 struct iwl4965_eeprom_calib_measure {
-        u8 temperature;
-        u8 gain_idx;
-        u8 actual_pow;
-        s8 pa_det;
+        u8 temperature;         /* Device temperature (Celsius) */
+        u8 gain_idx;            /* Index into gain table */
+        u8 actual_pow;          /* Measured RF output power, half-dBm */
+        s8 pa_det;              /* Power amp detector level (not used) */
 } __attribute__ ((packed));
 
+
+/*
+ * 4965 measurement set for one channel.  EEPROM contains:
+ *
+ * 1)  Channel number measured
+ *
+ * 2)  Measurements for each of 3 power levels for each of 2 radio transmitters
+ *     (a.k.a. "tx chains") (6 measurements altogether)
+ */
 struct iwl4965_eeprom_calib_ch_info {
         u8 ch_num;
         struct iwl4965_eeprom_calib_measure measurements[EEPROM_TX_POWER_TX_CHAINS]
                 [EEPROM_TX_POWER_MEASUREMENTS];
 } __attribute__ ((packed));
 
+/*
+ * 4965 txpower subband info.
+ *
+ * For each frequency subband, EEPROM contains the following:
+ *
+ * 1)  First and last channels within range of the subband.  "0" values
+ *     indicate that this sample set is not being used.
+ *
+ * 2)  Sample measurement sets for 2 channels close to the range endpoints.
+ */
 struct iwl4965_eeprom_calib_subband_info {
-        u8 ch_from;
-        u8 ch_to;
+        u8 ch_from;     /* channel number of lowest channel in subband */
+        u8 ch_to;       /* channel number of highest channel in subband */
         struct iwl4965_eeprom_calib_ch_info ch1;
         struct iwl4965_eeprom_calib_ch_info ch2;
 } __attribute__ ((packed));
 
+
+/*
+ * 4965 txpower calibration info.  EEPROM contains:
+ *
+ * 1)  Factory-measured saturation power levels (maximum levels at which
+ *     tx power amplifier can output a signal without too much distortion).
+ *     There is one level for 2.4 GHz band and one for 5 GHz band.  These
+ *     values apply to all channels within each of the bands.
+ *
+ * 2)  Factory-measured power supply voltage level.  This is assumed to be
+ *     constant (i.e. same value applies to all channels/bands) while the
+ *     factory measurements are being made.
+ *
+ * 3)  Up to 8 sets of factory-measured txpower calibration values.
+ *     These are for different frequency ranges, since txpower gain
+ *     characteristics of the analog radio circuitry vary with frequency.
+ *
+ *     Not all sets need to be filled with data;
+ *     struct iwl4965_eeprom_calib_subband_info contains range of channels
+ *     (0 if unused) for each set of data.
+ */
 struct iwl4965_eeprom_calib_info {
-        u8 saturation_power24;
-        u8 saturation_power52;
+        u8 saturation_power24;  /* half-dBm (e.g. "34" = 17 dBm) */
+        u8 saturation_power52;  /* half-dBm */
         s16 voltage;            /* signed */
         struct iwl4965_eeprom_calib_subband_info band_info[EEPROM_TX_POWER_BANDS];
 } __attribute__ ((packed));
 
 
+/*
+ * 4965 EEPROM map
+ */
 struct iwl4965_eeprom {
         u8 reserved0[16];
 #define EEPROM_DEVICE_ID                    (2*0x08)    /* 2 bytes */
-        u16 device_id;  /* abs.ofs: 16 */
+        u16 device_id;          /* abs.ofs: 16 */
         u8 reserved1[2];
 #define EEPROM_PMC                          (2*0x0A)    /* 2 bytes */
         u16 pmc;                /* abs.ofs: 20 */
@@ -273,40 +368,107 @@ struct iwl4965_eeprom {
         u8 reserved8[10];
 #define EEPROM_REGULATORY_SKU_ID            (2*0x60)    /* 4  bytes */
         u8 sku_id[4];           /* abs.ofs: 192 */
+
+/*
+ * Per-channel regulatory data.
+ *
+ * Each channel that *might* be supported by 3945 or 4965 has a fixed location
+ * in EEPROM containing EEPROM_CHANNEL_* usage flags (LSB) and max regulatory
+ * txpower (MSB).
+ *
+ * Entries immediately below are for 20 MHz channel width.  FAT (40 MHz)
+ * channels (only for 4965, not supported by 3945) appear later in the EEPROM.
+ *
+ * 2.4 GHz channels 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14
+ */
 #define EEPROM_REGULATORY_BAND_1            (2*0x62)    /* 2  bytes */
         u16 band_1_count;       /* abs.ofs: 196 */
 #define EEPROM_REGULATORY_BAND_1_CHANNELS   (2*0x63)    /* 28 bytes */
-        struct iwl4965_eeprom_channel band_1_channels[14];      /* abs.ofs: 196 */
+        struct iwl4965_eeprom_channel band_1_channels[14]; /* abs.ofs: 196 */
+
+/*
+ * 4.9 GHz channels 183, 184, 185, 187, 188, 189, 192, 196,
+ * 5.0 GHz channels 7, 8, 11, 12, 16
+ * (4915-5080MHz) (none of these is ever supported)
+ */
 #define EEPROM_REGULATORY_BAND_2            (2*0x71)    /* 2  bytes */
         u16 band_2_count;       /* abs.ofs: 226 */
 #define EEPROM_REGULATORY_BAND_2_CHANNELS   (2*0x72)    /* 26 bytes */
-        struct iwl4965_eeprom_channel band_2_channels[13];      /* abs.ofs: 228 */
+        struct iwl4965_eeprom_channel band_2_channels[13]; /* abs.ofs: 228 */
+
+/*
+ * 5.2 GHz channels 34, 36, 38, 40, 42, 44, 46, 48, 52, 56, 60, 64
+ * (5170-5320MHz)
+ */
 #define EEPROM_REGULATORY_BAND_3            (2*0x7F)    /* 2  bytes */
         u16 band_3_count;       /* abs.ofs: 254 */
 #define EEPROM_REGULATORY_BAND_3_CHANNELS   (2*0x80)    /* 24 bytes */
-        struct iwl4965_eeprom_channel band_3_channels[12];      /* abs.ofs: 256 */
+        struct iwl4965_eeprom_channel band_3_channels[12]; /* abs.ofs: 256 */
+
+/*
+ * 5.5 GHz channels 100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140
+ * (5500-5700MHz)
+ */
 #define EEPROM_REGULATORY_BAND_4            (2*0x8C)    /* 2  bytes */
         u16 band_4_count;       /* abs.ofs: 280 */
 #define EEPROM_REGULATORY_BAND_4_CHANNELS   (2*0x8D)    /* 22 bytes */
-        struct iwl4965_eeprom_channel band_4_channels[11];      /* abs.ofs: 282 */
+        struct iwl4965_eeprom_channel band_4_channels[11]; /* abs.ofs: 282 */
+
+/*
+ * 5.7 GHz channels 145, 149, 153, 157, 161, 165
+ * (5725-5825MHz)
+ */
 #define EEPROM_REGULATORY_BAND_5            (2*0x98)    /* 2  bytes */
         u16 band_5_count;       /* abs.ofs: 304 */
 #define EEPROM_REGULATORY_BAND_5_CHANNELS   (2*0x99)    /* 12 bytes */
-        struct iwl4965_eeprom_channel band_5_channels[6];       /* abs.ofs: 306 */
+        struct iwl4965_eeprom_channel band_5_channels[6]; /* abs.ofs: 306 */
 
         u8 reserved10[2];
+
+
+/*
+ * 2.4 GHz FAT channels 1 (5), 2 (6), 3 (7), 4 (8), 5 (9), 6 (10), 7 (11)
+ *
+ * The channel listed is the center of the lower 20 MHz half of the channel.
+ * The overall center frequency is actually 2 channels (10 MHz) above that,
+ * and the upper half of each FAT channel is centered 4 channels (20 MHz) away
+ * from the lower half; e.g. the upper half of FAT channel 1 is channel 5,
+ * and the overall FAT channel width centers on channel 3.
+ *
+ * NOTE:  The RXON command uses 20 MHz channel numbers to specify the
+ *        control channel to which to tune.  RXON also specifies whether the
+ *        control channel is the upper or lower half of a FAT channel.
+ *
+ * NOTE:  4965 does not support FAT channels on 2.4 GHz.
+ */
 #define EEPROM_REGULATORY_BAND_24_FAT_CHANNELS (2*0xA0) /* 14 bytes */
-        struct iwl4965_eeprom_channel band_24_channels[7];      /* abs.ofs: 320 */
+        struct iwl4965_eeprom_channel band_24_channels[7]; /* abs.ofs: 320 */
         u8 reserved11[2];
+
+/*
+ * 5.2 GHz FAT channels 36 (40), 44 (48), 52 (56), 60 (64),
+ * 100 (104), 108 (112), 116 (120), 124 (128), 132 (136), 149 (153), 157 (161)
+ */
 #define EEPROM_REGULATORY_BAND_52_FAT_CHANNELS (2*0xA8) /* 22 bytes */
-        struct iwl4965_eeprom_channel band_52_channels[11];     /* abs.ofs: 336 */
+        struct iwl4965_eeprom_channel band_52_channels[11]; /* abs.ofs: 336 */
         u8 reserved12[6];
+
+/*
+ * 4965 driver requires txpower calibration format version 5 or greater.
+ * Driver does not work with txpower calibration version < 5.
+ * This value is simply a 16-bit number, no major/minor versions here.
+ */
 #define EEPROM_CALIB_VERSION_OFFSET            (2*0xB6) /* 2 bytes */
         u16 calib_version;      /* abs.ofs: 364 */
         u8 reserved13[2];
+
 #define EEPROM_SATURATION_POWER_OFFSET         (2*0xB8) /* 2 bytes */
         u16 satruation_power;   /* abs.ofs: 368 */
         u8 reserved14[94];
+
+/*
+ * 4965 Txpower calibration data.
+ */
 #define EEPROM_IWL_CALIB_TXPOWER_OFFSET        (2*0xE8) /* 48  bytes */
         struct iwl4965_eeprom_calib_info calib_info;    /* abs.ofs: 464 */
 
@@ -317,6 +479,7 @@ struct iwl4965_eeprom {
 
 #define IWL_EEPROM_IMAGE_SIZE 1024
 
+/* End of EEPROM */
 
 #include "iwl-4965-commands.h"
 
diff --git a/drivers/net/wireless/iwlwifi/iwl-4965.c b/drivers/net/wireless/iwlwifi/iwl-4965.c
index 5dee8e512c7..7d95de9d034 100644
--- a/drivers/net/wireless/iwlwifi/iwl-4965.c
+++ b/drivers/net/wireless/iwlwifi/iwl-4965.c
@@ -4687,14 +4687,23 @@ struct pci_device_id iwl4965_hw_card_ids[] = {
         {0}
 };
 
+/*
+ * The device's EEPROM semaphore prevents conflicts between driver and uCode
+ * when accessing the EEPROM; each access is a series of pulses to/from the
+ * EEPROM chip, not a single event, so even reads could conflict if they
+ * weren't arbitrated by the semaphore.
+ */
 int iwl4965_eeprom_acquire_semaphore(struct iwl4965_priv *priv)
 {
         u16 count;
         int rc;
 
         for (count = 0; count < EEPROM_SEM_RETRY_LIMIT; count++) {
+                /* Request semaphore */
                 iwl4965_set_bit(priv, CSR_HW_IF_CONFIG_REG,
                         CSR_HW_IF_CONFIG_REG_BIT_EEPROM_OWN_SEM);
+
+                /* See if we got it */
                 rc = iwl4965_poll_bit(priv, CSR_HW_IF_CONFIG_REG,
                                         CSR_HW_IF_CONFIG_REG_BIT_EEPROM_OWN_SEM,
                                         CSR_HW_IF_CONFIG_REG_BIT_EEPROM_OWN_SEM,