some questions about uart_port

From: Chen Bin (sunwen_ling_at_tom.com)
Date: 03/07/04 

Date: 7 Mar 2004 05:23:42 -0800

Hi all,

Currently I am porting the old uart driver to linux's new uart
architecture,but I have no idea about some fields of the new uart's
structures.

struct uart_port {
        u_int iobase; /* in/out[bwl]
*/
        void *membase; /*
read/write[bwl] */
        u_int irq;
        u_int uartclk;
        u_char fifosize; /* tx fifo
size */
        u_char x_char;
        u_char regshift; /* reg offset
shift */
        u_char iotype; /* io access
style */
        u_char hub6;
        u_char unused[7];
        u_int read_status_mask;
        u_int ignore_status_mask;
        u_int flags;
        u_int type; /* port type
*/
        struct uart_ops *ops;
        struct uart_icount icount;
        u_int line;
        u_long mapbase; /* for ioremap
*/
};

What is the use of read_status_mask and ignore_status_mask?It is set
in change_speed function,but if I don't set it,what is the result?

And,what is the callout driver,must I provide this interface to the
kernel?

Thank you very much!

Chen Bin