Don't ingnore errors when setting baud rate

"Don't you think we should tell them that this baud rate is not
supported? Nah. Just smile and wave boys smile, smile and wave." While
this makes great movies, this does not make setting a knowingly
unsupported baud rate a great experience. At least when in comes to
debugging.

Play nice and report this and other errors related to baud rates back.

src/posix/termios.rs

@@ -213,11 +213,12 @@ pub(crate) fn set_stop_bits(termios: &mut Termios, stop_bits: StopBits) {
         ))
     )
 ))]
-pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) {
+pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) -> Result<()> {
     termios.c_cflag &= !nix::libc::CBAUD;
     termios.c_cflag |= nix::libc::BOTHER;
     termios.c_ispeed = baud_rate;
     termios.c_ospeed = baud_rate;
+    Ok(())
 }
 
 // BSDs use the baud rate as the constant value so there's no translation necessary
@@ -227,9 +228,10 @@ pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) {
     target_os = "netbsd",
     target_os = "openbsd"
 ))]
-pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) {
-    // Ignore the return value because this should never fail
-    unsafe { libc::cfsetspeed(termios, baud_rate.into()) };
+pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) -> Result<()> {
+    let res = unsafe { libc::cfsetspeed(termios, baud_rate.into()) };
+    nix::errno::Errno::result(res)?;
+    Ok(())
 }
 
 #[cfg(all(
@@ -240,7 +242,9 @@ pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) {
         target_arch = "powerpc64"
     )
 ))]
-pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) {
+pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) -> Result<()> {
+    use crate::{Error, ErrorKind};
+
     use self::libc::{
         B1000000, B1152000, B1500000, B2000000, B2500000, B3000000, B3500000, B4000000, B460800,
         B500000, B576000, B921600,
@@ -281,8 +285,9 @@ pub(crate) fn set_baud_rate(termios: &mut Termios, baud_rate: u32) {
         3_000_000 => B3000000,
         3_500_000 => B3500000,
         4_000_000 => B4000000,
-        _ => return,
+        _ => return Err(Error::new(ErrorKind::InvalidInput, "Unsupported baud rate")),
     };
     let res = unsafe { libc::cfsetspeed(termios, baud_rate) };
-    nix::errno::Errno::result(res).expect("cfsetspeed failed");
+    nix::errno::Errno::result(res)?;
+    Ok(())
 }

src/posix/tty.rs

@@ -176,7 +176,7 @@ impl TTYPort {
         termios::set_data_bits(&mut termios, builder.data_bits);
         termios::set_stop_bits(&mut termios, builder.stop_bits);
         #[cfg(not(any(target_os = "ios", target_os = "macos")))]
-        termios::set_baud_rate(&mut termios, builder.baud_rate);
+        termios::set_baud_rate(&mut termios, builder.baud_rate)?;
         #[cfg(any(target_os = "ios", target_os = "macos"))]
         termios::set_termios(fd.0, &termios, builder.baud_rate)?;
         #[cfg(not(any(target_os = "ios", target_os = "macos")))]
@@ -630,7 +630,7 @@ impl SerialPort for TTYPort {
     ))]
     fn set_baud_rate(&mut self, baud_rate: u32) -> Result<()> {
         let mut termios = termios::get_termios(self.fd)?;
-        termios::set_baud_rate(&mut termios, baud_rate);
+        termios::set_baud_rate(&mut termios, baud_rate)?;
         termios::set_termios(self.fd, &termios)
     }