143 lines
7.8 KiB
C
143 lines
7.8 KiB
C
/*****************************************************************************/
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/* UART_LOWLEV.C - Example user-defined device. */
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/*****************************************************************************/
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#include <file.h>
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#include "uart_drv.h"
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//#include "uart.h"
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/*****************************************************************************/
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//! //! <h1> Example user-defined device. </h1>
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/* This is a sample implementation of a user-defined device. The device */
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/* must define the seven basic functions (open, close, read, write, lseek, */
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/* unlink, rename). These are expected to behave just like the Unix */
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/* functions of these names. Some devices might not have a reasonable */
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/* action to take for some functions; a UART or TTY device might not be */
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/* lseek-able, but can still be opened and written to. A device is added */
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/* using the add_device() RTS function call (q.v.). */
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/*****************************************************************************/
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/* The low-level interface is based on file names and file descriptors. */
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/* The file names don't need to be valid Unix file names, but must mean */
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/* something to the device. The device must keep track of its own file */
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/* descriptors, which will be used by the calling functions to read and */
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/* write to the device. If there can only be one instance of a "file" on a */
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/* device, the file descriptor doesn't matter much, so just pass a */
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/* non-negative integer such as zero. */
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/*****************************************************************************/
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/*****************************************************************************/
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/* */
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/* UART_open() */
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/* */
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/*****************************************************************************/
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int UART_open(const char *path, unsigned flags, int llv_fd)
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{
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/*-----------------------------------------------------------------------*/
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/* Only one UART device exists (_SSA). For an _SSA device, file names */
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/* are not meaningful, so ignore the file name. */
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/*-----------------------------------------------------------------------*/
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/*-----------------------------------------------------------------------*/
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/* Don't allow attempts to open the UART device that aren't O_WRONLY. */
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/*-----------------------------------------------------------------------*/
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if (!(flags & O_WRONLY)) return -1;
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/*-----------------------------------------------------------------------*/
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/* Set up the UART */
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/*-----------------------------------------------------------------------*/
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UartSetup();
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/*-----------------------------------------------------------------------*/
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/* Arbitrarily give it file descriptor 1. File descriptors are */
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/* device-specific; this file descriptor 1 is not the same as HOST file */
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/* descriptor 1 (stdout). */
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/*-----------------------------------------------------------------------*/
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return 1;
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}
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/*****************************************************************************/
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/* */
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/* UART_close() */
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/* */
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/*****************************************************************************/
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int UART_close(int dev_fd)
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{
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/*-----------------------------------------------------------------------*/
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/* Only one UART device exists, so we don't do anything upon close. */
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/*-----------------------------------------------------------------------*/
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return 0;
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}
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/*****************************************************************************/
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/* */
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/* UART_read() reads *at most* count bytes. */
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/* */
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/*****************************************************************************/
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int UART_read(int dev_fd, char *buf, unsigned count)
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{
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/*-----------------------------------------------------------------------*/
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/* Only one UART device exists, and it is write-only, so return error */
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/*-----------------------------------------------------------------------*/
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return -1;
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}
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/*****************************************************************************/
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/* */
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/* UART_write() */
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/* */
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/*****************************************************************************/
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int UART_write(int dev_fd, const char *buf, unsigned count)
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{
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unsigned i;
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/*-----------------------------------------------------------------------*/
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/* Output character-by-character */
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/*-----------------------------------------------------------------------*/
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for (i=0; i < count; i++)
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UartPutChar(buf[i]);
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return count;
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}
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/*****************************************************************************/
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/* */
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/* UART_lseek() */
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/* */
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/*****************************************************************************/
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off_t UART_lseek(int dev_fd, off_t offset, int origin)
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{
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/*-----------------------------------------------------------------------*/
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/* lseek is not possible on UART. */
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/*-----------------------------------------------------------------------*/
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return -1;
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}
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/*****************************************************************************/
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/* */
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/* UART_unlink() */
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/* */
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/*****************************************************************************/
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int UART_unlink(const char *path)
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{
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/*-----------------------------------------------------------------------*/
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/* unlink is not possible on UART */
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/*-----------------------------------------------------------------------*/
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return -1;
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}
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/*****************************************************************************/
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/* */
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/* UART_rename() */
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/* */
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/*****************************************************************************/
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/* rename is unusual among the low-level functions in that it is also */
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/* specified in the ISO C standard. It has the same prototype and */
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/* semantics, so it's not really an issue. */
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/*****************************************************************************/
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int UART_rename(const char *old_name, const char *new_name)
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{
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/*-----------------------------------------------------------------------*/
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/* rename is not possible on UART */
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/*-----------------------------------------------------------------------*/
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return -1;
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}
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