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-rw-r--r--drivers/char/tty_ioctl.c45
1 files changed, 30 insertions, 15 deletions
diff --git a/drivers/char/tty_ioctl.c b/drivers/char/tty_ioctl.c
index dee47f40c6a..fd471cb3338 100644
--- a/drivers/char/tty_ioctl.c
+++ b/drivers/char/tty_ioctl.c
@@ -225,7 +225,7 @@ EXPORT_SYMBOL(tty_termios_input_baud_rate);
/**
* tty_termios_encode_baud_rate
- * @termios: termios structure
+ * @termios: ktermios structure holding user requested state
* @ispeed: input speed
* @ospeed: output speed
*
@@ -233,7 +233,10 @@ EXPORT_SYMBOL(tty_termios_input_baud_rate);
* used as a library helper for drivers os that they can report back
* the actual speed selected when it differs from the speed requested
*
- * For now input and output speed must agree.
+ * For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
+ * we need to carefully set the bits when the user does not get the
+ * desired speed. We allow small margins and preserve as much of possible
+ * of the input intent to keep compatiblity.
*
* Locking: Caller should hold termios lock. This is already held
* when calling this function from the driver termios handler.
@@ -242,32 +245,44 @@ EXPORT_SYMBOL(tty_termios_input_baud_rate);
void tty_termios_encode_baud_rate(struct ktermios *termios, speed_t ibaud, speed_t obaud)
{
int i = 0;
- int ifound = 0, ofound = 0;
+ int ifound = -1, ofound = -1;
+ int iclose = ibaud/50, oclose = obaud/50;
+ int ibinput = 0;
termios->c_ispeed = ibaud;
termios->c_ospeed = obaud;
+ /* If the user asked for a precise weird speed give a precise weird
+ answer. If they asked for a Bfoo speed they many have problems
+ digesting non-exact replies so fuzz a bit */
+
+ if ((termios->c_cflag & CBAUD) == BOTHER)
+ oclose = 0;
+ if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
+ iclose = 0;
+ if ((termios->c_cflag >> IBSHIFT) & CBAUD)
+ ibinput = 1; /* An input speed was specified */
+
termios->c_cflag &= ~CBAUD;
- /* Identical speed means no input encoding (ie B0 << IBSHIFT)*/
- if (termios->c_ispeed == termios->c_ospeed)
- ifound = 1;
do {
- if (obaud == baud_table[i]) {
+ if (obaud - oclose >= baud_table[i] && obaud + oclose <= baud_table[i]) {
termios->c_cflag |= baud_bits[i];
- ofound = 1;
- /* So that if ibaud == obaud we don't set it */
- continue;
+ ofound = i;
}
- if (ibaud == baud_table[i]) {
- termios->c_cflag |= (baud_bits[i] << IBSHIFT);
- ifound = 1;
+ if (ibaud - iclose >= baud_table[i] && ibaud + iclose <= baud_table[i]) {
+ /* For the case input == output don't set IBAUD bits if the user didn't do so */
+ if (ofound != i || ibinput)
+ termios->c_cflag |= (baud_bits[i] << IBSHIFT);
+ ifound = i;
}
}
while(++i < n_baud_table);
- if (!ofound)
+ if (ofound == -1)
termios->c_cflag |= BOTHER;
- if (!ifound)
+ /* Set exact input bits only if the input and output differ or the
+ user already did */
+ if (ifound == -1 && (ibaud != obaud || ibinput))
termios->c_cflag |= (BOTHER << IBSHIFT);
}