fix(tty): restore B3500000/B4000000 to baud_rate() and tidy constants

C1: B3500000 (0x0000100e) and B4000000 (0x0000100f) were
accidentally dropped from ControlMode::baud_rate() during the
v1→v2 dedup refactor.  Restore them — both speeds are defined in
the bitflags and covered by the CBAUD mask, so baud_rate() must
handle them or the constants should be removed (the former is correct).

L1: Move CIBAUD_SHIFT from between bitflags! and impl ControlMode
to the constant area near NCC / INIT_C_LINE_ABI.

L2: Merge duplicate header comment block in test_tty_termios.c
into a single clean file-level doc.

Author: DragonOS Dev

kernel/src/driver/tty/termios.rs

@@ -363,8 +363,6 @@ bitflags! {
 }
 
 
-/// Shift to extract input baud rate bits from c_cflag (CIBAUD = 0x100f0000).
-pub const CIBAUD_SHIFT: u32 = 16;
 
 impl ControlMode {
     /// 获取波特率
@@ -400,6 +398,8 @@ impl ControlMode {
             Self::B2000000 => Some(2000000),
             Self::B2500000 => Some(2500000),
             Self::B3000000 => Some(3000000),
+            Self::B3500000 => Some(3500000),
+            Self::B4000000 => Some(4000000),
             _ => None,
         }
     }
@@ -417,6 +417,9 @@ impl ControlMode {
 
 pub const NCC: usize = 8;
 
+/// Shift to extract input baud rate bits from c_cflag (CIBAUD = 0x100f0000).
+pub const CIBAUD_SHIFT: u32 = 16;
+
 /// Default c_line ABI value (N_TTY = 0).
 pub const INIT_C_LINE_ABI: u8 = 0;
 

user/apps/c_unitest/test_tty_termios.c

@@ -1,15 +1,13 @@
-// test_tty_termios.c — quick smoke test for TTY termios/termio ioctls.
-//
-// This file intentionally overlaps with dunitest/suites/normal/tty_termios.cc.
-// The C version is a fast, self-contained static binary for QEMU serial-console
-// smoke testing.  The C++ gtest version is the full CI regression suite.
-// Keep both: the C test catches regressions in environments where dunitest
-// (which requires gtest, a runner, and a rootfs) cannot run.
 // test_tty_termios.c — verify TCSAFLUSH / TCSADRAIN and legacy termio ioctls
 // on a valid TTY fd (PTY slave).
 //
 // Regression coverage for: "tcsetattr(0, TCSAFLUSH, &t) fails with ENOTTY"
 // and TCSETA/TCSETAW/TCSETAF/TCGETA returning ENOIOCTLCMD.
+//
+// This file intentionally overlaps with dunitest/suites/normal/tty_termios.cc.
+// The C version is a fast, self-contained static binary for QEMU smoke testing.
+// The C++ gtest version is the full CI regression suite.  Keep both: the C test
+// catches regressions in environments where dunitest cannot run.
 
 #include <errno.h>
 #include <fcntl.h>