Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 2953 insertions, 0 deletions

diff --git a/drivers/atm/horizon.c b/drivers/atm/horizon.c
new file mode 100644
index 000000000000..924a2c8988bd
--- /dev/null
+++ b/drivers/atm/horizon.c
@@ -0,0 +1,2953 @@
+/*
+  Madge Horizon ATM Adapter driver.
+  Copyright (C) 1995-1999  Madge Networks Ltd.
+  
+  This program is free software; you can redistribute it and/or modify
+  it under the terms of the GNU General Public License as published by
+  the Free Software Foundation; either version 2 of the License, or
+  (at your option) any later version.
+  
+  This program is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+  GNU General Public License for more details.
+  
+  You should have received a copy of the GNU General Public License
+  along with this program; if not, write to the Free Software
+  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+  
+  The GNU GPL is contained in /usr/doc/copyright/GPL on a Debian
+  system and in the file COPYING in the Linux kernel source.
+*/
+
+/*
+  IMPORTANT NOTE: Madge Networks no longer makes the adapters
+  supported by this driver and makes no commitment to maintain it.
+*/
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/mm.h>
+#include <linux/pci.h>
+#include <linux/errno.h>
+#include <linux/atm.h>
+#include <linux/atmdev.h>
+#include <linux/sonet.h>
+#include <linux/skbuff.h>
+#include <linux/time.h>
+#include <linux/delay.h>
+#include <linux/uio.h>
+#include <linux/init.h>
+#include <linux/ioport.h>
+#include <linux/wait.h>
+
+#include <asm/system.h>
+#include <asm/io.h>
+#include <asm/atomic.h>
+#include <asm/uaccess.h>
+#include <asm/string.h>
+#include <asm/byteorder.h>
+
+#include "horizon.h"
+
+#define maintainer_string "Giuliano Procida at Madge Networks <gprocida@madge.com>"
+#define description_string "Madge ATM Horizon [Ultra] driver"
+#define version_string "1.2.1"
+
+static inline void __init show_version (void) {
+  printk ("%s version %s\n", description_string, version_string);
+}
+
+/*
+  
+  CREDITS
+  
+  Driver and documentation by:
+  
+  Chris Aston        Madge Networks
+  Giuliano Procida   Madge Networks
+  Simon Benham       Madge Networks
+  Simon Johnson      Madge Networks
+  Various Others     Madge Networks
+  
+  Some inspiration taken from other drivers by:
+  
+  Alexandru Cucos    UTBv
+  Kari Mettinen      University of Helsinki
+  Werner Almesberger EPFL LRC
+  
+  Theory of Operation
+  
+  I Hardware, detection, initialisation and shutdown.
+  
+  1. Supported Hardware
+  
+  This driver should handle all variants of the PCI Madge ATM adapters
+  with the Horizon chipset. These are all PCI cards supporting PIO, BM
+  DMA and a form of MMIO (registers only, not internal RAM).
+  
+  The driver is only known to work with SONET and UTP Horizon Ultra
+  cards at 155Mb/s. However, code is in place to deal with both the
+  original Horizon and 25Mb/s operation.
+  
+  There are two revisions of the Horizon ASIC: the original and the
+  Ultra. Details of hardware bugs are in section III.
+  
+  The ASIC version can be distinguished by chip markings but is NOT
+  indicated by the PCI revision (all adapters seem to have PCI rev 1).
+  
+  I believe that:
+  
+  Horizon       => Collage  25 PCI Adapter (UTP and STP)
+  Horizon Ultra => Collage 155 PCI Client (UTP or SONET)
+  Ambassador x  => Collage 155 PCI Server (completely different)
+  
+  Horizon (25Mb/s) is fitted with UTP and STP connectors. It seems to
+  have a Madge B154 plus glue logic serializer. I have also found a
+  really ancient version of this with slightly different glue. It
+  comes with the revision 0 (140-025-01) ASIC.
+  
+  Horizon Ultra (155Mb/s) is fitted with either a Pulse Medialink
+  output (UTP) or an HP HFBR 5205 output (SONET). It has either
+  Madge's SAMBA framer or a SUNI-lite device (early versions). It
+  comes with the revision 1 (140-027-01) ASIC.
+  
+  2. Detection
+  
+  All Horizon-based cards present with the same PCI Vendor and Device
+  IDs. The standard Linux 2.2 PCI API is used to locate any cards and
+  to enable bus-mastering (with appropriate latency).
+  
+  ATM_LAYER_STATUS in the control register distinguishes between the
+  two possible physical layers (25 and 155). It is not clear whether
+  the 155 cards can also operate at 25Mbps. We rely on the fact that a
+  card operates at 155 if and only if it has the newer Horizon Ultra
+  ASIC.
+  
+  For 155 cards the two possible framers are probed for and then set
+  up for loop-timing.
+  
+  3. Initialisation
+  
+  The card is reset and then put into a known state. The physical
+  layer is configured for normal operation at the appropriate speed;
+  in the case of the 155 cards, the framer is initialised with
+  line-based timing; the internal RAM is zeroed and the allocation of
+  buffers for RX and TX is made; the Burnt In Address is read and
+  copied to the ATM ESI; various policy settings for RX (VPI bits,
+  unknown VCs, oam cells) are made. Ideally all policy items should be
+  configurable at module load (if not actually on-demand), however,
+  only the vpi vs vci bit allocation can be specified at insmod.
+  
+  4. Shutdown
+  
+  This is in response to module_cleaup. No VCs are in use and the card
+  should be idle; it is reset.
+  
+  II Driver software (as it should be)
+  
+  0. Traffic Parameters
+  
+  The traffic classes (not an enumeration) are currently: ATM_NONE (no
+  traffic), ATM_UBR, ATM_CBR, ATM_VBR and ATM_ABR, ATM_ANYCLASS
+  (compatible with everything). Together with (perhaps only some of)
+  the following items they make up the traffic specification.
+  
+  struct atm_trafprm {
+    unsigned char traffic_class; traffic class (ATM_UBR, ...)
+    int           max_pcr;       maximum PCR in cells per second
+    int           pcr;           desired PCR in cells per second
+    int           min_pcr;       minimum PCR in cells per second
+    int           max_cdv;       maximum CDV in microseconds
+    int           max_sdu;       maximum SDU in bytes
+  };
+  
+  Note that these denote bandwidth available not bandwidth used; the
+  possibilities according to ATMF are:
+  
+  Real Time (cdv and max CDT given)
+  
+  CBR(pcr)             pcr bandwidth always available
+  rtVBR(pcr,scr,mbs)   scr bandwidth always available, upto pcr at mbs too
+  
+  Non Real Time
+  
+  nrtVBR(pcr,scr,mbs)  scr bandwidth always available, upto pcr at mbs too
+  UBR()
+  ABR(mcr,pcr)         mcr bandwidth always available, upto pcr (depending) too
+  
+  mbs is max burst size (bucket)
+  pcr and scr have associated cdvt values
+  mcr is like scr but has no cdtv
+  cdtv may differ at each hop
+  
+  Some of the above items are qos items (as opposed to traffic
+  parameters). We have nothing to do with qos. All except ABR can have
+  their traffic parameters converted to GCRA parameters. The GCRA may
+  be implemented as a (real-number) leaky bucket. The GCRA can be used
+  in complicated ways by switches and in simpler ways by end-stations.
+  It can be used both to filter incoming cells and shape out-going
+  cells.
+  
+  ATM Linux actually supports:
+  
+  ATM_NONE() (no traffic in this direction)
+  ATM_UBR(max_frame_size)
+  ATM_CBR(max/min_pcr, max_cdv, max_frame_size)
+  
+  0 or ATM_MAX_PCR are used to indicate maximum available PCR
+  
+  A traffic specification consists of the AAL type and separate
+  traffic specifications for either direction. In ATM Linux it is:
+  
+  struct atm_qos {
+  struct atm_trafprm txtp;
+  struct atm_trafprm rxtp;
+  unsigned char aal;
+  };
+  
+  AAL types are:
+  
+  ATM_NO_AAL    AAL not specified
+  ATM_AAL0      "raw" ATM cells
+  ATM_AAL1      AAL1 (CBR)
+  ATM_AAL2      AAL2 (VBR)
+  ATM_AAL34     AAL3/4 (data)
+  ATM_AAL5      AAL5 (data)
+  ATM_SAAL      signaling AAL
+  
+  The Horizon has support for AAL frame types: 0, 3/4 and 5. However,
+  it does not implement AAL 3/4 SAR and it has a different notion of
+  "raw cell" to ATM Linux's (48 bytes vs. 52 bytes) so neither are
+  supported by this driver.
+  
+  The Horizon has limited support for ABR (including UBR), VBR and
+  CBR. Each TX channel has a bucket (containing up to 31 cell units)
+  and two timers (PCR and SCR) associated with it that can be used to
+  govern cell emissions and host notification (in the case of ABR this
+  is presumably so that RM cells may be emitted at appropriate times).
+  The timers may either be disabled or may be set to any of 240 values
+  (determined by the clock crystal, a fixed (?) per-device divider, a
+  configurable divider and a configurable timer preload value).
+  
+  At the moment only UBR and CBR are supported by the driver. VBR will
+  be supported as soon as ATM for Linux supports it. ABR support is
+  very unlikely as RM cell handling is completely up to the driver.
+  
+  1. TX (TX channel setup and TX transfer)
+  
+  The TX half of the driver owns the TX Horizon registers. The TX
+  component in the IRQ handler is the BM completion handler. This can
+  only be entered when tx_busy is true (enforced by hardware). The
+  other TX component can only be entered when tx_busy is false
+  (enforced by driver). So TX is single-threaded.
+  
+  Apart from a minor optimisation to not re-select the last channel,
+  the TX send component works as follows:
+  
+  Atomic test and set tx_busy until we succeed; we should implement
+  some sort of timeout so that tx_busy will never be stuck at true.
+  
+  If no TX channel is set up for this VC we wait for an idle one (if
+  necessary) and set it up.
+  
+  At this point we have a TX channel ready for use. We wait for enough
+  buffers to become available then start a TX transmit (set the TX
+  descriptor, schedule transfer, exit).
+  
+  The IRQ component handles TX completion (stats, free buffer, tx_busy
+  unset, exit). We also re-schedule further transfers for the same
+  frame if needed.
+  
+  TX setup in more detail:
+  
+  TX open is a nop, the relevant information is held in the hrz_vcc
+  (vcc->dev_data) structure and is "cached" on the card.
+  
+  TX close gets the TX lock and clears the channel from the "cache".
+  
+  2. RX (Data Available and RX transfer)
+  
+  The RX half of the driver owns the RX registers. There are two RX
+  components in the IRQ handler: the data available handler deals with
+  fresh data that has arrived on the card, the BM completion handler
+  is very similar to the TX completion handler. The data available
+  handler grabs the rx_lock and it is only released once the data has
+  been discarded or completely transferred to the host. The BM
+  completion handler only runs when the lock is held; the data
+  available handler is locked out over the same period.
+  
+  Data available on the card triggers an interrupt. If the data is not
+  suitable for our existing RX channels or we cannot allocate a buffer
+  it is flushed. Otherwise an RX receive is scheduled. Multiple RX
+  transfers may be scheduled for the same frame.
+  
+  RX setup in more detail:
+  
+  RX open...
+  RX close...
+  
+  III Hardware Bugs
+  
+  0. Byte vs Word addressing of adapter RAM.
+  
+  A design feature; see the .h file (especially the memory map).
+  
+  1. Bus Master Data Transfers (original Horizon only, fixed in Ultra)
+  
+  The host must not start a transmit direction transfer at a
+  non-four-byte boundary in host memory. Instead the host should
+  perform a byte, or a two byte, or one byte followed by two byte
+  transfer in order to start the rest of the transfer on a four byte
+  boundary. RX is OK.
+  
+  Simultaneous transmit and receive direction bus master transfers are
+  not allowed.
+  
+  The simplest solution to these two is to always do PIO (never DMA)
+  in the TX direction on the original Horizon. More complicated
+  solutions are likely to hurt my brain.
+  
+  2. Loss of buffer on close VC
+  
+  When a VC is being closed, the buffer associated with it is not
+  returned to the pool. The host must store the reference to this
+  buffer and when opening a new VC then give it to that new VC.
+  
+  The host intervention currently consists of stacking such a buffer
+  pointer at VC close and checking the stack at VC open.
+  
+  3. Failure to close a VC
+  
+  If a VC is currently receiving a frame then closing the VC may fail
+  and the frame continues to be received.
+  
+  The solution is to make sure any received frames are flushed when
+  ready. This is currently done just before the solution to 2.
+  
+  4. PCI bus (original Horizon only, fixed in Ultra)
+  
+  Reading from the data port prior to initialisation will hang the PCI
+  bus. Just don't do that then! We don't.
+  
+  IV To Do List
+  
+  . Timer code may be broken.
+  
+  . Allow users to specify buffer allocation split for TX and RX.
+  
+  . Deal once and for all with buggy VC close.
+  
+  . Handle interrupted and/or non-blocking operations.
+  
+  . Change some macros to functions and move from .h to .c.
+  
+  . Try to limit the number of TX frames each VC may have queued, in
+    order to reduce the chances of TX buffer exhaustion.
+  
+  . Implement VBR (bucket and timers not understood) and ABR (need to
+    do RM cells manually); also no Linux support for either.
+  
+  . Implement QoS changes on open VCs (involves extracting parts of VC open
+    and close into separate functions and using them to make changes).
+  
+*/
+
+/********** globals **********/
+
+static void do_housekeeping (unsigned long arg);
+
+static unsigned short debug = 0;
+static unsigned short vpi_bits = 0;
+static int max_tx_size = 9000;
+static int max_rx_size = 9000;
+static unsigned char pci_lat = 0;
+
+/********** access functions **********/
+
+/* Read / Write Horizon registers */
+static inline void wr_regl (const hrz_dev * dev, unsigned char reg, u32 data) {
+  outl (cpu_to_le32 (data), dev->iobase + reg);
+}
+
+static inline u32 rd_regl (const hrz_dev * dev, unsigned char reg) {
+  return le32_to_cpu (inl (dev->iobase + reg));
+}
+
+static inline void wr_regw (const hrz_dev * dev, unsigned char reg, u16 data) {
+  outw (cpu_to_le16 (data), dev->iobase + reg);
+}
+
+static inline u16 rd_regw (const hrz_dev * dev, unsigned char reg) {
+  return le16_to_cpu (inw (dev->iobase + reg));
+}
+
+static inline void wrs_regb (const hrz_dev * dev, unsigned char reg, void * addr, u32 len) {
+  outsb (dev->iobase + reg, addr, len);
+}
+
+static inline void rds_regb (const hrz_dev * dev, unsigned char reg, void * addr, u32 len) {
+  insb (dev->iobase + reg, addr, len);
+}
+
+/* Read / Write to a given address in Horizon buffer memory.
+   Interrupts must be disabled between the address register and data
+   port accesses as these must form an atomic operation. */
+static inline void wr_mem (const hrz_dev * dev, HDW * addr, u32 data) {
+  // wr_regl (dev, MEM_WR_ADDR_REG_OFF, (u32) addr);
+  wr_regl (dev, MEM_WR_ADDR_REG_OFF, (addr - (HDW *) 0) * sizeof(HDW));
+  wr_regl (dev, MEMORY_PORT_OFF, data);
+}
+
+static inline u32 rd_mem (const hrz_dev * dev, HDW * addr) {
+  // wr_regl (dev, MEM_RD_ADDR_REG_OFF, (u32) addr);
+  wr_regl (dev, MEM_RD_ADDR_REG_OFF, (addr - (HDW *) 0) * sizeof(HDW));
+  return rd_regl (dev, MEMORY_PORT_OFF);
+}
+
+static inline void wr_framer (const hrz_dev * dev, u32 addr, u32 data) {
+  wr_regl (dev, MEM_WR_ADDR_REG_OFF, (u32) addr | 0x80000000);
+  wr_regl (dev, MEMORY_PORT_OFF, data);
+}
+
+static inline u32 rd_framer (const hrz_dev * dev, u32 addr) {
+  wr_regl (dev, MEM_RD_ADDR_REG_OFF, (u32) addr | 0x80000000);
+  return rd_regl (dev, MEMORY_PORT_OFF);
+}
+
+/********** specialised access functions **********/
+
+/* RX */
+
+static inline void FLUSH_RX_CHANNEL (hrz_dev * dev, u16 channel) {
+  wr_regw (dev, RX_CHANNEL_PORT_OFF, FLUSH_CHANNEL | channel);
+  return;
+}
+
+static inline void WAIT_FLUSH_RX_COMPLETE (hrz_dev * dev) {
+  while (rd_regw (dev, RX_CHANNEL_PORT_OFF) & FLUSH_CHANNEL)
+    ;
+  return;
+}
+
+static inline void SELECT_RX_CHANNEL (hrz_dev * dev, u16 channel) {
+  wr_regw (dev, RX_CHANNEL_PORT_OFF, channel);
+  return;
+}
+
+static inline void WAIT_UPDATE_COMPLETE (hrz_dev * dev) {
+  while (rd_regw (dev, RX_CHANNEL_PORT_OFF) & RX_CHANNEL_UPDATE_IN_PROGRESS)
+    ;
+  return;
+}
+
+/* TX */
+
+static inline void SELECT_TX_CHANNEL (hrz_dev * dev, u16 tx_channel) {
+  wr_regl (dev, TX_CHANNEL_PORT_OFF, tx_channel);
+  return;
+}
+
+/* Update or query one configuration parameter of a particular channel. */
+
+static inline void update_tx_channel_config (hrz_dev * dev, short chan, u8 mode, u16 value) {
+  wr_regw (dev, TX_CHANNEL_CONFIG_COMMAND_OFF,
+	   chan * TX_CHANNEL_CONFIG_MULT | mode);
+    wr_regw (dev, TX_CHANNEL_CONFIG_DATA_OFF, value);
+    return;
+}
+
+static inline u16 query_tx_channel_config (hrz_dev * dev, short chan, u8 mode) {
+  wr_regw (dev, TX_CHANNEL_CONFIG_COMMAND_OFF,
+	   chan * TX_CHANNEL_CONFIG_MULT | mode);
+    return rd_regw (dev, TX_CHANNEL_CONFIG_DATA_OFF);
+}
+
+/********** dump functions **********/
+
+static inline void dump_skb (char * prefix, unsigned int vc, struct sk_buff * skb) {
+#ifdef DEBUG_HORIZON
+  unsigned int i;
+  unsigned char * data = skb->data;
+  PRINTDB (DBG_DATA, "%s(%u) ", prefix, vc);
+  for (i=0; i<skb->len && i < 256;i++)
+    PRINTDM (DBG_DATA, "%02x ", data[i]);
+  PRINTDE (DBG_DATA,"");
+#else
+  (void) prefix;
+  (void) vc;
+  (void) skb;
+#endif
+  return;
+}
+
+static inline void dump_regs (hrz_dev * dev) {
+#ifdef DEBUG_HORIZON
+  PRINTD (DBG_REGS, "CONTROL 0: %#x", rd_regl (dev, CONTROL_0_REG));
+  PRINTD (DBG_REGS, "RX CONFIG: %#x", rd_regw (dev, RX_CONFIG_OFF));
+  PRINTD (DBG_REGS, "TX CONFIG: %#x", rd_regw (dev, TX_CONFIG_OFF));
+  PRINTD (DBG_REGS, "TX STATUS: %#x", rd_regw (dev, TX_STATUS_OFF));
+  PRINTD (DBG_REGS, "IRQ ENBLE: %#x", rd_regl (dev, INT_ENABLE_REG_OFF));
+  PRINTD (DBG_REGS, "IRQ SORCE: %#x", rd_regl (dev, INT_SOURCE_REG_OFF));
+#else
+  (void) dev;
+#endif
+  return;
+}
+
+static inline void dump_framer (hrz_dev * dev) {
+#ifdef DEBUG_HORIZON
+  unsigned int i;
+  PRINTDB (DBG_REGS, "framer registers:");
+  for (i = 0; i < 0x10; ++i)
+    PRINTDM (DBG_REGS, " %02x", rd_framer (dev, i));
+  PRINTDE (DBG_REGS,"");
+#else
+  (void) dev;
+#endif
+  return;
+}
+
+/********** VPI/VCI <-> (RX) channel conversions **********/
+
+/* RX channels are 10 bit integers, these fns are quite paranoid */
+
+static inline int channel_to_vpivci (const u16 channel, short * vpi, int * vci) {
+  unsigned short vci_bits = 10 - vpi_bits;
+  if ((channel & RX_CHANNEL_MASK) == channel) {
+    *vci = channel & ((~0)<<vci_bits);
+    *vpi = channel >> vci_bits;
+    return channel ? 0 : -EINVAL;
+  }
+  return -EINVAL;
+}
+
+static inline int vpivci_to_channel (u16 * channel, const short vpi, const int vci) {
+  unsigned short vci_bits = 10 - vpi_bits;
+  if (0 <= vpi && vpi < 1<<vpi_bits && 0 <= vci && vci < 1<<vci_bits) {
+    *channel = vpi<<vci_bits | vci;
+    return *channel ? 0 : -EINVAL;
+  }
+  return -EINVAL;
+}
+
+/********** decode RX queue entries **********/
+
+static inline u16 rx_q_entry_to_length (u32 x) {
+  return x & RX_Q_ENTRY_LENGTH_MASK;
+}
+
+static inline u16 rx_q_entry_to_rx_channel (u32 x) {
+  return (x>>RX_Q_ENTRY_CHANNEL_SHIFT) & RX_CHANNEL_MASK;
+}
+
+/* Cell Transmit Rate Values
+ *
+ * the cell transmit rate (cells per sec) can be set to a variety of
+ * different values by specifying two parameters: a timer preload from
+ * 1 to 16 (stored as 0 to 15) and a clock divider (2 to the power of
+ * an exponent from 0 to 14; the special value 15 disables the timer).
+ *
+ * cellrate = baserate / (preload * 2^divider)
+ *
+ * The maximum cell rate that can be specified is therefore just the
+ * base rate. Halving the preload is equivalent to adding 1 to the
+ * divider and so values 1 to 8 of the preload are redundant except
+ * in the case of a maximal divider (14).
+ *
+ * Given a desired cell rate, an algorithm to determine the preload
+ * and divider is:
+ * 
+ * a) x = baserate / cellrate, want p * 2^d = x (as far as possible)
+ * b) if x > 16 * 2^14 then set p = 16, d = 14 (min rate), done
+ *    if x <= 16 then set p = x, d = 0 (high rates), done
+ * c) now have 16 < x <= 2^18, or 1 < x/16 <= 2^14 and we want to
+ *    know n such that 2^(n-1) < x/16 <= 2^n, so slide a bit until
+ *    we find the range (n will be between 1 and 14), set d = n
+ * d) Also have 8 < x/2^n <= 16, so set p nearest x/2^n
+ *
+ * The algorithm used below is a minor variant of the above.
+ *
+ * The base rate is derived from the oscillator frequency (Hz) using a
+ * fixed divider:
+ *
+ * baserate = freq / 32 in the case of some Unknown Card
+ * baserate = freq / 8  in the case of the Horizon        25
+ * baserate = freq / 8  in the case of the Horizon Ultra 155
+ *
+ * The Horizon cards have oscillators and base rates as follows:
+ *
+ * Card               Oscillator  Base Rate
+ * Unknown Card       33 MHz      1.03125 MHz (33 MHz = PCI freq)
+ * Horizon        25  32 MHz      4       MHz
+ * Horizon Ultra 155  40 MHz      5       MHz
+ *
+ * The following defines give the base rates in Hz. These were
+ * previously a factor of 100 larger, no doubt someone was using
+ * cps*100.
+ */
+
+#define BR_UKN 1031250l
+#define BR_HRZ 4000000l
+#define BR_ULT 5000000l
+
+// d is an exponent
+#define CR_MIND 0
+#define CR_MAXD 14
+
+// p ranges from 1 to a power of 2
+#define CR_MAXPEXP 4
+ 
+static int make_rate (const hrz_dev * dev, u32 c, rounding r,
+		      u16 * bits, unsigned int * actual)
+{
+	// note: rounding the rate down means rounding 'p' up
+	const unsigned long br = test_bit(ultra, &dev->flags) ? BR_ULT : BR_HRZ;
+  
+	u32 div = CR_MIND;
+	u32 pre;
+  
+	// br_exp and br_man are used to avoid overflowing (c*maxp*2^d) in
+	// the tests below. We could think harder about exact possibilities
+	// of failure...
+  
+	unsigned long br_man = br;
+	unsigned int br_exp = 0;
+  
+	PRINTD (DBG_QOS|DBG_FLOW, "make_rate b=%lu, c=%u, %s", br, c,
+		r == round_up ? "up" : r == round_down ? "down" : "nearest");
+  
+	// avoid div by zero
+	if (!c) {
+		PRINTD (DBG_QOS|DBG_ERR, "zero rate is not allowed!");
+		return -EINVAL;
+	}
+  
+	while (br_exp < CR_MAXPEXP + CR_MIND && (br_man % 2 == 0)) {
+		br_man = br_man >> 1;
+		++br_exp;
+	}
+	// (br >>br_exp) <<br_exp == br and
+	// br_exp <= CR_MAXPEXP+CR_MIND
+  
+	if (br_man <= (c << (CR_MAXPEXP+CR_MIND-br_exp))) {
+		// Equivalent to: B <= (c << (MAXPEXP+MIND))
+		// take care of rounding
+		switch (r) {
+			case round_down:
+				pre = (br+(c<<div)-1)/(c<<div);
+				// but p must be non-zero
+				if (!pre)
+					pre = 1;
+				break;
+			case round_nearest:
+				pre = (br+(c<<div)/2)/(c<<div);
+				// but p must be non-zero
+				if (!pre)
+					pre = 1;
+				break;
+			default:	/* round_up */
+				pre = br/(c<<div);
+				// but p must be non-zero
+				if (!pre)
+					return -EINVAL;
+		}
+		PRINTD (DBG_QOS, "A: p=%u, d=%u", pre, div);
+		goto got_it;
+	}
+  
+	// at this point we have
+	// d == MIND and (c << (MAXPEXP+MIND)) < B
+	while (div < CR_MAXD) {
+		div++;
+		if (br_man <= (c << (CR_MAXPEXP+div-br_exp))) {
+			// Equivalent to: B <= (c << (MAXPEXP+d))
+			// c << (MAXPEXP+d-1) < B <= c << (MAXPEXP+d)
+			// 1 << (MAXPEXP-1) < B/2^d/c <= 1 << MAXPEXP
+			// MAXP/2 < B/c2^d <= MAXP
+			// take care of rounding
+			switch (r) {
+				case round_down:
+					pre = (br+(c<<div)-1)/(c<<div);
+					break;
+				case round_nearest:
+					pre = (br+(c<<div)/2)/(c<<div);
+					break;
+				default: /* round_up */
+					pre = br/(c<<div);
+			}
+			PRINTD (DBG_QOS, "B: p=%u, d=%u", pre, div);
+			goto got_it;
+		}
+	}
+	// at this point we have
+	// d == MAXD and (c << (MAXPEXP+MAXD)) < B
+	// but we cannot go any higher
+	// take care of rounding
+	if (r == round_down)
+		return -EINVAL;
+	pre = 1 << CR_MAXPEXP;
+	PRINTD (DBG_QOS, "C: p=%u, d=%u", pre, div);
+got_it:
+	// paranoia
+	if (div > CR_MAXD || (!pre) || pre > 1<<CR_MAXPEXP) {
+		PRINTD (DBG_QOS, "set_cr internal failure: d=%u p=%u",
+			div, pre);
+		return -EINVAL;
+	} else {
+		if (bits)
+			*bits = (div<<CLOCK_SELECT_SHIFT) | (pre-1);
+		if (actual) {
+			*actual = (br + (pre<<div) - 1) / (pre<<div);
+			PRINTD (DBG_QOS, "actual rate: %u", *actual);
+		}
+		return 0;
+	}
+}
+
+static int make_rate_with_tolerance (const hrz_dev * dev, u32 c, rounding r, unsigned int tol,
+				     u16 * bit_pattern, unsigned int * actual) {
+  unsigned int my_actual;
+  
+  PRINTD (DBG_QOS|DBG_FLOW, "make_rate_with_tolerance c=%u, %s, tol=%u",
+	  c, (r == round_up) ? "up" : (r == round_down) ? "down" : "nearest", tol);
+  
+  if (!actual)
+    // actual rate is not returned
+    actual = &my_actual;
+  
+  if (make_rate (dev, c, round_nearest, bit_pattern, actual))
+    // should never happen as round_nearest always succeeds
+    return -1;
+  
+  if (c - tol <= *actual && *actual <= c + tol)
+    // within tolerance
+    return 0;
+  else
+    // intolerant, try rounding instead
+    return make_rate (dev, c, r, bit_pattern, actual);
+}
+
+/********** Listen on a VC **********/
+
+static int hrz_open_rx (hrz_dev * dev, u16 channel) {
+  // is there any guarantee that we don't get two simulataneous
+  // identical calls of this function from different processes? yes
+  // rate_lock
+  unsigned long flags;
+  u32 channel_type; // u16?
+  
+  u16 buf_ptr = RX_CHANNEL_IDLE;
+  
+  rx_ch_desc * rx_desc = &memmap->rx_descs[channel];
+  
+  PRINTD (DBG_FLOW, "hrz_open_rx %x", channel);
+  
+  spin_lock_irqsave (&dev->mem_lock, flags);
+  channel_type = rd_mem (dev, &rx_desc->wr_buf_type) & BUFFER_PTR_MASK;
+  spin_unlock_irqrestore (&dev->mem_lock, flags);
+  
+  // very serious error, should never occur
+  if (channel_type != RX_CHANNEL_DISABLED) {
+    PRINTD (DBG_ERR|DBG_VCC, "RX channel for VC already open");
+    return -EBUSY; // clean up?
+  }
+  
+  // Give back spare buffer
+  if (dev->noof_spare_buffers) {
+    buf_ptr = dev->spare_buffers[--dev->noof_spare_buffers];
+    PRINTD (DBG_VCC, "using a spare buffer: %u", buf_ptr);
+    // should never occur
+    if (buf_ptr == RX_CHANNEL_DISABLED || buf_ptr == RX_CHANNEL_IDLE) {
+      // but easy to recover from
+      PRINTD (DBG_ERR|DBG_VCC, "bad spare buffer pointer, using IDLE");
+      buf_ptr = RX_CHANNEL_IDLE;
+    }
+  } else {
+    PRINTD (DBG_VCC, "using IDLE buffer pointer");
+  }
+  
+  // Channel is currently disabled so change its status to idle
+  
+  // do we really need to save the flags again?
+  spin_lock_irqsave (&dev->mem_lock, flags);
+  
+  wr_mem (dev, &rx_desc->wr_buf_type,
+	  buf_ptr | CHANNEL_TYPE_AAL5 | FIRST_CELL_OF_AAL5_FRAME);
+  if (buf_ptr != RX_CHANNEL_IDLE)
+    wr_mem (dev, &rx_desc->rd_buf_type, buf_ptr);
+  
+  spin_unlock_irqrestore (&dev->mem_lock, flags);
+  
+  // rxer->rate = make_rate (qos->peak_cells);
+  
+  PRINTD (DBG_FLOW, "hrz_open_rx ok");
+  
+  return 0;
+}
+
+#if 0
+/********** change vc rate for a given vc **********/
+
+static void hrz_change_vc_qos (ATM_RXER * rxer, MAAL_QOS * qos) {
+  rxer->rate = make_rate (qos->peak_cells);
+}
+#endif
+
+/********** free an skb (as per ATM device driver documentation) **********/
+
+static inline void hrz_kfree_skb (struct sk_buff * skb) {
+  if (ATM_SKB(skb)->vcc->pop) {
+    ATM_SKB(skb)->vcc->pop (ATM_SKB(skb)->vcc, skb);
+  } else {
+    dev_kfree_skb_any (skb);
+  }
+}
+
+/********** cancel listen on a VC **********/
+
+static void hrz_close_rx (hrz_dev * dev, u16 vc) {
+  unsigned long flags;
+  
+  u32 value;
+  
+  u32 r1, r2;
+  
+  rx_ch_desc * rx_desc = &memmap->rx_descs[vc];
+  
+  int was_idle = 0;
+  
+  spin_lock_irqsave (&dev->mem_lock, flags);
+  value = rd_mem (dev, &rx_desc->wr_buf_type) & BUFFER_PTR_MASK;
+  spin_unlock_irqrestore (&dev->mem_lock, flags);
+  
+  if (value == RX_CHANNEL_DISABLED) {
+    // I suppose this could happen once we deal with _NONE traffic properly
+    PRINTD (DBG_VCC, "closing VC: RX channel %u already disabled", vc);
+    return;
+  }
+  if (value == RX_CHANNEL_IDLE)
+    was_idle = 1;
+  
+  spin_lock_irqsave (&dev->mem_lock, flags);
+  
+  for (;;) {
+    wr_mem (dev, &rx_desc->wr_buf_type, RX_CHANNEL_DISABLED);
+    
+    if ((rd_mem (dev, &rx_desc->wr_buf_type) & BUFFER_PTR_MASK) == RX_CHANNEL_DISABLED)
+      break;
+    
+    was_idle = 0;
+  }
+  
+  if (was_idle) {
+    spin_unlock_irqrestore (&dev->mem_lock, flags);
+    return;
+  }
+  
+  WAIT_FLUSH_RX_COMPLETE(dev);
+  
+  // XXX Is this all really necessary? We can rely on the rx_data_av
+  // handler to discard frames that remain queued for delivery. If the
+  // worry is that immediately reopening the channel (perhaps by a
+  // different process) may cause some data to be mis-delivered then
+  // there may still be a simpler solution (such as busy-waiting on
+  // rx_busy once the channel is disabled or before a new one is
+  // opened - does this leave any holes?). Arguably setting up and
+  // tearing down the TX and RX halves of each virtual circuit could
+  // most safely be done within ?x_busy protected regions.
+  
+  // OK, current changes are that Simon's marker is disabled and we DO
+  // look for NULL rxer elsewhere. The code here seems flush frames
+  // and then remember the last dead cell belonging to the channel
+  // just disabled - the cell gets relinked at the next vc_open.
+  // However, when all VCs are closed or only a few opened there are a
+  // handful of buffers that are unusable.
+  
+  // Does anyone feel like documenting spare_buffers properly?
+  // Does anyone feel like fixing this in a nicer way?
+  
+  // Flush any data which is left in the channel
+  for (;;) {
+    // Change the rx channel port to something different to the RX
+    // channel we are trying to close to force Horizon to flush the rx
+    // channel read and write pointers.
+    
+    u16 other = vc^(RX_CHANS/2);
+    
+    SELECT_RX_CHANNEL (dev, other);
+    WAIT_UPDATE_COMPLETE (dev);
+    
+    r1 = rd_mem (dev, &rx_desc->rd_buf_type);
+    
+    // Select this RX channel. Flush doesn't seem to work unless we
+    // select an RX channel before hand
+    
+    SELECT_RX_CHANNEL (dev, vc);
+    WAIT_UPDATE_COMPLETE (dev);
+    
+    // Attempt to flush a frame on this RX channel
+    
+    FLUSH_RX_CHANNEL (dev, vc);
+    WAIT_FLUSH_RX_COMPLETE (dev);
+    
+    // Force Horizon to flush rx channel read and write pointers as before
+    
+    SELECT_RX_CHANNEL (dev, other);
+    WAIT_UPDATE_COMPLETE (dev);
+    
+    r2 = rd_mem (dev, &rx_desc->rd_buf_type);
+    
+    PRINTD (DBG_VCC|DBG_RX, "r1 = %u, r2 = %u", r1, r2);
+    
+    if (r1 == r2) {
+      dev->spare_buffers[dev->noof_spare_buffers++] = (u16)r1;
+      break;
+    }
+  }
+  
+#if 0
+  {
+    rx_q_entry * wr_ptr = &memmap->rx_q_entries[rd_regw (dev, RX_QUEUE_WR_PTR_OFF)];
+    rx_q_entry * rd_ptr = dev->rx_q_entry;
+    
+    PRINTD (DBG_VCC|DBG_RX, "rd_ptr = %u, wr_ptr = %u", rd_ptr, wr_ptr);
+    
+    while (rd_ptr != wr_ptr) {
+      u32 x = rd_mem (dev, (HDW *) rd_ptr);
+      
+      if (vc == rx_q_entry_to_rx_channel (x)) {
+	x |= SIMONS_DODGEY_MARKER;
+	
+	PRINTD (DBG_RX|DBG_VCC|DBG_WARN, "marking a frame as dodgey");
+	
+	wr_mem (dev, (HDW *) rd_ptr, x);
+      }
+      
+      if (rd_ptr == dev->rx_q_wrap)
+	rd_ptr = dev->rx_q_reset;
+      else
+	rd_ptr++;
+    }
+  }
+#endif
+  
+  spin_unlock_irqrestore (&dev->mem_lock, flags);
+  
+  return;
+}
+
+/********** schedule RX transfers **********/
+
+// Note on tail recursion: a GCC developer said that it is not likely
+// to be fixed soon, so do not define TAILRECUSRIONWORKS unless you
+// are sure it does as you may otherwise overflow the kernel stack.
+
+// giving this fn a return value would help GCC, alledgedly
+
+static void rx_schedule (hrz_dev * dev, int irq) {
+  unsigned int rx_bytes;
+  
+  int pio_instead = 0;
+#ifndef TAILRECURSIONWORKS
+  pio_instead = 1;
+  while (pio_instead) {
+#endif
+    // bytes waiting for RX transfer
+    rx_bytes = dev->rx_bytes;
+    
+#if 0
+    spin_count = 0;
+    while (rd_regl (dev, MASTER_RX_COUNT_REG_OFF)) {
+      PRINTD (DBG_RX|DBG_WARN, "RX error: other PCI Bus Master RX still in progress!");
+      if (++spin_count > 10) {
+	PRINTD (DBG_RX|DBG_ERR, "spun out waiting PCI Bus Master RX completion");
+	wr_regl (dev, MASTER_RX_COUNT_REG_OFF, 0);
+	clear_bit (rx_busy, &dev->flags);
+	hrz_kfree_skb (dev->rx_skb);
+	return;
+      }
+    }
+#endif
+    
+    // this code follows the TX code but (at the moment) there is only
+    // one region - the skb itself. I don't know if this will change,
+    // but it doesn't hurt to have the code here, disabled.
+    
+    if (rx_bytes) {
+      // start next transfer within same region
+      if (rx_bytes <= MAX_PIO_COUNT) {
+	PRINTD (DBG_RX|DBG_BUS, "(pio)");
+	pio_instead = 1;
+      }
+      if (rx_bytes <= MAX_TRANSFER_COUNT) {
+	PRINTD (DBG_RX|DBG_BUS, "(simple or last multi)");
+	dev->rx_bytes = 0;
+      } else {
+	PRINTD (DBG_RX|DBG_BUS, "(continuing multi)");
+	dev->rx_bytes = rx_bytes - MAX_TRANSFER_COUNT;
+	rx_bytes = MAX_TRANSFER_COUNT;
+      }
+    } else {
+      // rx_bytes == 0 -- we're between regions
+      // regions remaining to transfer
+#if 0
+      unsigned int rx_regions = dev->rx_regions;
+#else
+      unsigned int rx_regions = 0;
+#endif
+      
+      if (rx_regions) {
+#if 0
+	// start a new region
+	dev->rx_addr = dev->rx_iovec->iov_base;
+	rx_bytes = dev->rx_iovec->iov_len;
+	++dev->rx_iovec;
+	dev->rx_regions = rx_regions - 1;
+	
+	if (rx_bytes <= MAX_PIO_COUNT) {
+	  PRINTD (DBG_RX|DBG_BUS, "(pio)");
+	  pio_instead = 1;
+	}
+	if (rx_bytes <= MAX_TRANSFER_COUNT) {
+	  PRINTD (DBG_RX|DBG_BUS, "(full region)");
+	  dev->rx_bytes = 0;
+	} else {
+	  PRINTD (DBG_RX|DBG_BUS, "(start multi region)");
+	  dev->rx_bytes = rx_bytes - MAX_TRANSFER_COUNT;
+	  rx_bytes = MAX_TRANSFER_COUNT;
+	}
+#endif
+      } else {
+	// rx_regions == 0
+	// that's all folks - end of frame
+	struct sk_buff * skb = dev->rx_skb;
+	// dev->rx_iovec = 0;
+	
+	FLUSH_RX_CHANNEL (dev, dev->rx_channel);
+	
+	dump_skb ("<<<", dev->rx_channel, skb);
+	
+	PRINTD (DBG_RX|DBG_SKB, "push %p %u", skb->data, skb->len);
+	
+	{
+	  struct atm_vcc * vcc = ATM_SKB(skb)->vcc;
+	  // VC layer stats
+	  atomic_inc(&vcc->stats->rx);
+	  do_gettimeofday(&skb->stamp);
+	  // end of our responsability
+	  vcc->push (vcc, skb);
+	}
+      }
+    }
+    
+