libbb/speed_table.c: expand comments

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/libbb/speed_table.c b/libbb/speed_table.c
index 13dc9c73a54c13eb76aa6c4b001c455d389110f6..11ced01d0ce00b2e8cfde62dd53e8c448d0d5f1c 100644 (file)
--- a/libbb/speed_table.c
+++ b/libbb/speed_table.c
@@ -103,8 +103,23 @@ static const struct speed_map speeds[] = {
        {B4000000, 4000000/200 + 0x8000u},
 #endif
 /* 4000000/200 = 0x4e20, bit#15 still does not interfere with the value */
+/* (can use /800 if higher speeds would appear, /1600 won't work for B500000) */
 };
 
+/*
+ * TODO: maybe we can just bite the bullet, ditch the table and use termios2
+ * Linux API (supports arbitrary baud rates, no Bxxxx mess needed)? Example:
+ *
+ * #include <asm/termios.h>
+ * #include <asm/ioctls.h>
+ * struct termios2 t;
+ * ioctl(fd, TCGETS2, &t);
+ * t.c_ospeed = t.c_ispeed = 543210;
+ * t.c_cflag &= ~CBAUD;
+ * t.c_cflag |= BOTHER;
+ * ioctl(fd, TCSETS2, &t);
+ */
+
 enum { NUM_SPEEDS = ARRAY_SIZE(speeds) };
 
 unsigned FAST_FUNC tty_baud_to_value(speed_t speed)
@@ -114,7 +129,7 @@ unsigned FAST_FUNC tty_baud_to_value(speed_t speed)
        do {
                if (speed == speeds[i].speed) {
                        if (speeds[i].value & 0x8000u) {
-                               return ((unsigned long) (speeds[i].value) & 0x7fffU) * 200;
+                               return ((unsigned)(speeds[i].value) & 0x7fffU) * 200;
                        }
                        return speeds[i].value;
                }