doc/016-serial-ports/Serial.tex

61 CPU drivers use serial port access for printing debug information,
65 Each CPU driver implements a serial port subsystem which provides a
89 Each port must be initialized before it can be used:
91   extern errval\_t serial\_init(unsigned port);
94 the port cannot be initialized, or the port number is out of range.
96 Initializing a serial port more than once, however, is permissible:
97 subsequent attempts to initialize an initialized port are silently
99 console and debug logical ports share the same physical port.
106   extern errval\_t serial\_early\_init(unsigned port);
110 bug to call this function more than once with the same port number,
115 Each serial port provides polled, blocking, single-character
118   extern void serial\_putchar(unsigned port, char c);
119   extern char serial\_getchar(unsigned port);
121 It is a bug to call these with a port number that is out of range
125 these functions on a serial port which has not yet been initialized
137 \item The \emph{console} port is used for general logging and debug
141 \item The \emph{debug} port can be used to attach an external debugger
146 the serial port implementation, but they can be changed by writing
154 the same physical port.
157 physical port is currently assigned to a logical port:
164 \texttt{serial\_getchar()} with the appropriate port number:
177 \section{Implementing a serial port subsystem}
182 The serial port subsystem for a CPU driver must implement all the
187   errval_t serial_init(unsigned port);
188   errval_t serial_early_init(unsigned port);
189   void serial_putchar(unsigned port, char c);
190   char serial_getchar(unsigned port);
198 Initializing a serial port typically consists of configuring the UART
202 Examples of serial port implementations at time of writing include: