[PATCH stable v2 2/2] termios, tty/tty_baudrate.c: simplify, auto-generate baud table
From: H. Peter Anvin
Date: Mon Oct 08 2018 - 00:07:30 EST
From: "H. Peter Anvin (Intel)" <hpa@xxxxxxxxx>
Now when all architectures define BOTHER and IBSHIFT, we can
unconditionally rely on these constants. Furthermore, the code can be
significantly simplified in a number of places.
Rather than having two tables and needing to be able to keep them in
sync at all times, have one auto-generated table. This also lets us
avoid the fact that architectures that have CBAUDEX == 0 have BOTHER
in a different location that those that don't.
The code for masking CBAUDEX as a fallback is never exercised on any
architecture, because for all architectures, either the baud rate
table is completely defined for all CBAUD values, or CBAUDEX == 0, so
we can just remove it.
Finally, this patch avoids overrunning the baud_table[] for
architectures with CBAUDEX == 0.
Signed-off-by: H. Peter Anvin (Intel) <hpa@xxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Jiri Slaby <jslaby@xxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Richard Henderson <rth@xxxxxxxxxxx>
Cc: Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>
Cc: Matt Turner <mattst88@xxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Kate Stewart <kstewart@xxxxxxxxxxxxxxxxxxx>
Cc: Philippe Ombredanne <pombredanne@xxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Eugene Syromiatnikov <esyr@xxxxxxxxxx>
Cc: <linux-alpha@xxxxxxxxxxxxxxx>
Cc: <linux-serial@xxxxxxxxxxxxxxx>
Cc: Johan Hovold <johan@xxxxxxxxxx>
Cc: Alan Cox <alan@xxxxxxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
---
drivers/tty/.gitignore | 1 +
drivers/tty/Makefile | 16 ++++
drivers/tty/bmacros.c | 2 +
drivers/tty/tty_baudrate.c | 182 ++++++++++++++-----------------------
4 files changed, 85 insertions(+), 116 deletions(-)
create mode 100644 drivers/tty/.gitignore
create mode 100644 drivers/tty/bmacros.c
diff --git a/drivers/tty/.gitignore b/drivers/tty/.gitignore
new file mode 100644
index 000000000000..d436c18a912c
--- /dev/null
+++ b/drivers/tty/.gitignore
@@ -0,0 +1 @@
+bmacros.h
diff --git a/drivers/tty/Makefile b/drivers/tty/Makefile
index c72cafdf32b4..489b222ab1ce 100644
--- a/drivers/tty/Makefile
+++ b/drivers/tty/Makefile
@@ -35,3 +35,19 @@ obj-$(CONFIG_MIPS_EJTAG_FDC_TTY) += mips_ejtag_fdc.o
obj-$(CONFIG_VCC) += vcc.o
obj-y += ipwireless/
+
+#
+# Rules for generating the baud rate table
+#
+CFLAGS_bmacros.o += -Wp,-dM
+
+$(obj)/tty_baudrate.o: $(obj)/bmacros.h
+
+quiet_cmd_bmacros = BMACROS $@
+ cmd_bmacros = ( \
+ sed -nr -e 's/^.define B([0-9]+) .*$$/BTBL(B\1,\1)/p' $< \
+ | sort -n -k1.7 > $@ ) || (rm -f $@ ; echo false)
+
+targets += bmacros.h
+$(obj)/bmacros.h: $(obj)/bmacros.i FORCE
+ $(call if_changed,bmacros)
diff --git a/drivers/tty/bmacros.c b/drivers/tty/bmacros.c
new file mode 100644
index 000000000000..0af865ff00de
--- /dev/null
+++ b/drivers/tty/bmacros.c
@@ -0,0 +1,2 @@
+/* This file is used to extract the B... macros from header files */
+#include <linux/termios.h>
diff --git a/drivers/tty/tty_baudrate.c b/drivers/tty/tty_baudrate.c
index 7576ceace571..ec6d3d93ffac 100644
--- a/drivers/tty/tty_baudrate.c
+++ b/drivers/tty/tty_baudrate.c
@@ -9,43 +9,48 @@
#include <linux/tty.h>
#include <linux/export.h>
-
/*
- * Routine which returns the baud rate of the tty
- *
- * Note that the baud_table needs to be kept in sync with the
- * include/asm/termbits.h file.
+ * Routine which returns the baud rate of the tty. The B... constants
+ * are extracted from the appropriate header files via
+ * bmacros.c -> bmacros.h.
*/
-static const speed_t baud_table[] = {
- 0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
- 9600, 19200, 38400, 57600, 115200, 230400, 460800,
-#ifdef __sparc__
- 76800, 153600, 307200, 614400, 921600
-#else
- 500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
- 2500000, 3000000, 3500000, 4000000
+
+/* CBAUD mask with CBAUDEX removed */
+#define CBAUDNX (CBAUD & ~CBAUDEX)
+
+/* Lowest bit in CBAUDEX, if any. CBAUDEX is assumed contiguous. */
+#define CBAUDEL (CBAUDEX & ~(CBAUDEX << 1))
+#if CBAUDEL & (CBAUDEL-1)
+# error "CBAUDEX is not contiguous"
#endif
-};
-#ifndef __sparc__
-static const tcflag_t baud_bits[] = {
- B0, B50, B75, B110, B134, B150, B200, B300, B600,
- B1200, B1800, B2400, B4800, B9600, B19200, B38400,
- B57600, B115200, B230400, B460800, B500000, B576000,
- B921600, B1000000, B1152000, B1500000, B2000000, B2500000,
- B3000000, B3500000, B4000000
-};
-#else
-static const tcflag_t baud_bits[] = {
- B0, B50, B75, B110, B134, B150, B200, B300, B600,
- B1200, B1800, B2400, B4800, B9600, B19200, B38400,
- B57600, B115200, B230400, B460800, B76800, B153600,
- B307200, B614400, B921600
+/* Convert from B... constant to table position */
+#define BPOS(x) (((x) & CBAUDNX) + \
+ (CBAUDEX ? ((x) & CBAUDEX)/CBAUDEL*(CBAUDNX+1) : 0))
+
+/* Convert from table position to B... constant */
+#define BVAL(x) (((x) & CBAUDNX) + (((x)/(CBAUDNX+1)*CBAUDEX) & CBAUDEX))
+
+/* Entry into the baud_table */
+#define BTBL(b,v) [BPOS(b)] = (v),
+
+static const speed_t baud_table[] = {
+#include "bmacros.h"
};
-#endif
static int n_baud_table = ARRAY_SIZE(baud_table);
+/* Helper function; will be called with cbaud already masked */
+static speed_t _tty_termios_baud_rate(unsigned int cbaud, speed_t bother_speed)
+{
+ /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
+ if (cbaud == BOTHER)
+ return bother_speed;
+
+ cbaud = BPOS(cbaud);
+ return (cbaud >= n_baud_table) ? 0 : baud_table[cbaud];
+}
+
/**
* tty_termios_baud_rate
* @termios: termios structure
@@ -60,24 +65,8 @@ static int n_baud_table = ARRAY_SIZE(baud_table);
speed_t tty_termios_baud_rate(struct ktermios *termios)
{
- unsigned int cbaud;
-
- cbaud = termios->c_cflag & CBAUD;
-
-#ifdef BOTHER
- /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
- if (cbaud == BOTHER)
- return termios->c_ospeed;
-#endif
- if (cbaud & CBAUDEX) {
- cbaud &= ~CBAUDEX;
-
- if (cbaud < 1 || cbaud + 15 > n_baud_table)
- termios->c_cflag &= ~CBAUDEX;
- else
- cbaud += 15;
- }
- return baud_table[cbaud];
+ return _tty_termios_baud_rate(termios->c_cflag & CBAUD,
+ termios->c_ospeed);
}
EXPORT_SYMBOL(tty_termios_baud_rate);
@@ -95,28 +84,15 @@ EXPORT_SYMBOL(tty_termios_baud_rate);
speed_t tty_termios_input_baud_rate(struct ktermios *termios)
{
-#ifdef IBSHIFT
- unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
-
- if (cbaud == B0)
- return tty_termios_baud_rate(termios);
-#ifdef BOTHER
- /* Magic token for arbitrary speed via c_ispeed*/
- if (cbaud == BOTHER)
- return termios->c_ispeed;
-#endif
- if (cbaud & CBAUDEX) {
- cbaud &= ~CBAUDEX;
+ unsigned int cbaud;
+ speed_t bother_speed = termios->c_ispeed;
- if (cbaud < 1 || cbaud + 15 > n_baud_table)
- termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
- else
- cbaud += 15;
+ cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;
+ if (cbaud == B0) {
+ cbaud = termios->c_cflag & CBAUD;
+ bother_speed = termios->c_ospeed;
}
- return baud_table[cbaud];
-#else /* IBSHIFT */
- return tty_termios_baud_rate(termios);
-#endif /* IBSHIFT */
+ return _tty_termios_baud_rate(cbaud, bother_speed);
}
EXPORT_SYMBOL(tty_termios_input_baud_rate);
@@ -145,38 +121,27 @@ 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 = -1, ofound = -1;
+ int i;
+ unsigned int ifound, ofound;
int iclose = ibaud/50, oclose = obaud/50;
- int ibinput = 0;
+ bool ibinput = false;
- if (obaud == 0) /* CD dropped */
+ if (obaud == 0) /* CD dropped */
ibaud = 0; /* Clear ibaud to be sure */
termios->c_ispeed = ibaud;
termios->c_ospeed = obaud;
-#ifdef IBSHIFT
- if ((termios->c_cflag >> IBSHIFT) & CBAUD)
- ibinput = 1; /* An input speed was specified */
-#endif
-#ifdef BOTHER
+ ibinput = ((termios->c_cflag >> IBSHIFT) & CBAUD) != B0;
+
/* If the user asked for a precise weird speed give a precise weird
answer. If they asked for a Bfoo speed they may have problems
digesting non-exact replies so fuzz a bit */
- if ((termios->c_cflag & CBAUD) == BOTHER) {
+ if ((termios->c_cflag & CBAUD) == BOTHER)
oclose = 0;
- if (!ibinput)
- iclose = 0;
- }
if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
iclose = 0;
-#endif
- termios->c_cflag &= ~CBAUD;
-#ifdef IBSHIFT
- termios->c_cflag &= ~(CBAUD << IBSHIFT);
-#endif
/*
* Our goal is to find a close match to the standard baud rate
@@ -184,43 +149,28 @@ void tty_termios_encode_baud_rate(struct ktermios *termios,
* match then report back the speed as a POSIX Bxxxx value by
* preference
*/
-
- do {
+ ofound = ifound = BOTHER;
+ for (i = 0; i < n_baud_table; i++) {
if (obaud - oclose <= baud_table[i] &&
obaud + oclose >= baud_table[i]) {
- termios->c_cflag |= baud_bits[i];
- ofound = i;
+ ofound = BVAL(i);
+ break;
}
- 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)
- ifound = i;
-#ifdef IBSHIFT
- else {
- ifound = i;
- termios->c_cflag |= (baud_bits[i] << IBSHIFT);
+ }
+ if (!ibinput) {
+ ifound = 0;
+ } else {
+ for (i = 0; i < n_baud_table; i++) {
+ if (ibaud - iclose <= baud_table[i] &&
+ ibaud + iclose >= baud_table[i]) {
+ ifound = BVAL(i);
+ break;
}
-#endif
}
- } while (++i < n_baud_table);
+ }
- /*
- * If we found no match then use BOTHER if provided or warn
- * the user their platform maintainer needs to wake up if not.
- */
-#ifdef BOTHER
- if (ofound == -1)
- termios->c_cflag |= BOTHER;
- /* 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);
-#else
- if (ifound == -1 || ofound == -1)
- pr_warn_once("tty: Unable to return correct speed data as your architecture needs updating.\n");
-#endif
+ termios->c_cflag &= ~(CBAUD | (CBAUD << IBSHIFT));
+ termios->c_cflag |= ofound | (ifound << IBSHIFT);
}
EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);
--
2.17.1