drivers/tty/tty_baudrate.c

   1 /*
   2  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
   3  */
   4
   5 #include <linux/types.h>
   6 #include <linux/kernel.h>
   7 #include <linux/termios.h>
   8 #include <linux/tty.h>
   9 #include <linux/export.h>
  10
  11
  12 /*
  13  * Routine which returns the baud rate of the tty
  14  *
  15  * Note that the baud_table needs to be kept in sync with the
  16  * include/asm/termbits.h file.
  17  */
  18 static const speed_t baud_table[] = {
  19         0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
  20         9600, 19200, 38400, 57600, 115200, 230400, 460800,
  21 #ifdef __sparc__
  22         76800, 153600, 307200, 614400, 921600
  23 #else
  24         500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
  25         2500000, 3000000, 3500000, 4000000
  26 #endif
  27 };
  28
  29 #ifndef __sparc__
  30 static const tcflag_t baud_bits[] = {
  31         B0, B50, B75, B110, B134, B150, B200, B300, B600,
  32         B1200, B1800, B2400, B4800, B9600, B19200, B38400,
  33         B57600, B115200, B230400, B460800, B500000, B576000,
  34         B921600, B1000000, B1152000, B1500000, B2000000, B2500000,
  35         B3000000, B3500000, B4000000
  36 };
  37 #else
  38 static const tcflag_t baud_bits[] = {
  39         B0, B50, B75, B110, B134, B150, B200, B300, B600,
  40         B1200, B1800, B2400, B4800, B9600, B19200, B38400,
  41         B57600, B115200, B230400, B460800, B76800, B153600,
  42         B307200, B614400, B921600
  43 };
  44 #endif
  45
  46 static int n_baud_table = ARRAY_SIZE(baud_table);
  47
  48 /**
  49  *      tty_termios_baud_rate
  50  *      @termios: termios structure
  51  *
  52  *      Convert termios baud rate data into a speed. This should be called
  53  *      with the termios lock held if this termios is a terminal termios
  54  *      structure. May change the termios data. Device drivers can call this
  55  *      function but should use ->c_[io]speed directly as they are updated.
  56  *
  57  *      Locking: none
  58  */
  59
  60 speed_t tty_termios_baud_rate(struct ktermios *termios)
  61 {
  62         unsigned int cbaud;
  63
  64         cbaud = termios->c_cflag & CBAUD;
  65
  66 #ifdef BOTHER
  67         /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
  68         if (cbaud == BOTHER)
  69                 return termios->c_ospeed;
  70 #endif
  71         if (cbaud & CBAUDEX) {
  72                 cbaud &= ~CBAUDEX;
  73
  74                 if (cbaud < 1 || cbaud + 15 > n_baud_table)
  75                         termios->c_cflag &= ~CBAUDEX;
  76                 else
  77                         cbaud += 15;
  78         }
  79         return baud_table[cbaud];
  80 }
  81 EXPORT_SYMBOL(tty_termios_baud_rate);
  82
  83 /**
  84  *      tty_termios_input_baud_rate
  85  *      @termios: termios structure
  86  *
  87  *      Convert termios baud rate data into a speed. This should be called
  88  *      with the termios lock held if this termios is a terminal termios
  89  *      structure. May change the termios data. Device drivers can call this
  90  *      function but should use ->c_[io]speed directly as they are updated.
  91  *
  92  *      Locking: none
  93  */
  94
  95 speed_t tty_termios_input_baud_rate(struct ktermios *termios)
  96 {
  97 #ifdef IBSHIFT
  98         unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
  99
 100         if (cbaud == B0)
 101                 return tty_termios_baud_rate(termios);
 102
 103         /* Magic token for arbitrary speed via c_ispeed*/
 104         if (cbaud == BOTHER)
 105                 return termios->c_ispeed;
 106
 107         if (cbaud & CBAUDEX) {
 108                 cbaud &= ~CBAUDEX;
 109
 110                 if (cbaud < 1 || cbaud + 15 > n_baud_table)
 111                         termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
 112                 else
 113                         cbaud += 15;
 114         }
 115         return baud_table[cbaud];
 116 #else
 117         return tty_termios_baud_rate(termios);
 118 #endif
 119 }
 120 EXPORT_SYMBOL(tty_termios_input_baud_rate);
 121
 122 /**
 123  *      tty_termios_encode_baud_rate
 124  *      @termios: ktermios structure holding user requested state
 125  *      @ispeed: input speed
 126  *      @ospeed: output speed
 127  *
 128  *      Encode the speeds set into the passed termios structure. This is
 129  *      used as a library helper for drivers so that they can report back
 130  *      the actual speed selected when it differs from the speed requested
 131  *
 132  *      For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
 133  *      we need to carefully set the bits when the user does not get the
 134  *      desired speed. We allow small margins and preserve as much of possible
 135  *      of the input intent to keep compatibility.
 136  *
 137  *      Locking: Caller should hold termios lock. This is already held
 138  *      when calling this function from the driver termios handler.
 139  *
 140  *      The ifdefs deal with platforms whose owners have yet to update them
 141  *      and will all go away once this is done.
 142  */
 143
 144 void tty_termios_encode_baud_rate(struct ktermios *termios,
 145                                   speed_t ibaud, speed_t obaud)
 146 {
 147         int i = 0;
 148         int ifound = -1, ofound = -1;
 149         int iclose = ibaud/50, oclose = obaud/50;
 150         int ibinput = 0;
 151
 152         if (obaud == 0)                 /* CD dropped             */
 153                 ibaud = 0;              /* Clear ibaud to be sure */
 154
 155         termios->c_ispeed = ibaud;
 156         termios->c_ospeed = obaud;
 157
 158 #ifdef BOTHER
 159         /* If the user asked for a precise weird speed give a precise weird
 160            answer. If they asked for a Bfoo speed they may have problems
 161            digesting non-exact replies so fuzz a bit */
 162
 163         if ((termios->c_cflag & CBAUD) == BOTHER)
 164                 oclose = 0;
 165         if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
 166                 iclose = 0;
 167         if ((termios->c_cflag >> IBSHIFT) & CBAUD)
 168                 ibinput = 1;    /* An input speed was specified */
 169 #endif
 170         termios->c_cflag &= ~CBAUD;
 171
 172         /*
 173          *      Our goal is to find a close match to the standard baud rate
 174          *      returned. Walk the baud rate table and if we get a very close
 175          *      match then report back the speed as a POSIX Bxxxx value by
 176          *      preference
 177          */
 178
 179         do {
 180                 if (obaud - oclose <= baud_table[i] &&
 181                     obaud + oclose >= baud_table[i]) {
 182                         termios->c_cflag |= baud_bits[i];
 183                         ofound = i;
 184                 }
 185                 if (ibaud - iclose <= baud_table[i] &&
 186                     ibaud + iclose >= baud_table[i]) {
 187                         /* For the case input == output don't set IBAUD bits
 188                            if the user didn't do so */
 189                         if (ofound == i && !ibinput)
 190                                 ifound  = i;
 191 #ifdef IBSHIFT
 192                         else {
 193                                 ifound = i;
 194                                 termios->c_cflag |= (baud_bits[i] << IBSHIFT);
 195                         }
 196 #endif
 197                 }
 198         } while (++i < n_baud_table);
 199
 200         /*
 201          *      If we found no match then use BOTHER if provided or warn
 202          *      the user their platform maintainer needs to wake up if not.
 203          */
 204 #ifdef BOTHER
 205         if (ofound == -1)
 206                 termios->c_cflag |= BOTHER;
 207         /* Set exact input bits only if the input and output differ or the
 208            user already did */
 209         if (ifound == -1 && (ibaud != obaud || ibinput))
 210                 termios->c_cflag |= (BOTHER << IBSHIFT);
 211 #else
 212         if (ifound == -1 || ofound == -1)
 213                 pr_warn_once("tty: Unable to return correct speed data as your architecture needs updating.\n");
 214 #endif
 215 }
 216 EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
 217
 218 /**
 219  *      tty_encode_baud_rate            -       set baud rate of the tty
 220  *      @ibaud: input baud rate
 221  *      @obad: output baud rate
 222  *
 223  *      Update the current termios data for the tty with the new speed
 224  *      settings. The caller must hold the termios_rwsem for the tty in
 225  *      question.
 226  */
 227
 228 void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
 229 {
 230         tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
 231 }
 232 EXPORT_SYMBOL_GPL(tty_encode_baud_rate);