[archieval]

Hi,

I am currently developing a low level serial driver to be registered with serial_core.c (in latest 2.6. kernel source), and I have a couple of questions about it.

Should serial_core.c be compiled with my driver? In the Makefile, should there be something like... ?

obj-m := serial_core.o myserial.o

And also, what does the algorithm of this code means (also found in drivers/serial/uart00.c of latest 2.6 kernel source)?

59 static void uart_tx_chars(struct uart_port *port)
 60 {
 61         struct circ_buf *xmit = &port->info->xmit;
 62         int count;
 63 
 64         if (port->x_char) {
 65                 pr_debug("wrote %2x", port->x_char);
 66                 port->icount.tx++;
 67                 port->x_char = 0;
 68                 return;
 69         }
 70         if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
 71                 tiny_stop_tx(port);
 72                 return;
 73         }
 74 
 75         count = port->fifosize >> 1;
 76         do {
 77                 
 78                 xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
 79                 port->icount.tx++;
 80                 if (uart_circ_empty(xmit))
 81                         break;
 82         } while (--count > 0);
 83 
 84         if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
 85                 uart_write_wakeup(port);
 86 
 87         if (uart_circ_empty(xmit))
 88                 tiny_stop_tx(port);
 89 }

what is the purpose of shifting in "count = port->fifosize >> 1"?

Thanks!

[matt_kleviar]

can you please tell what does port->fifosize refer to ?