Re: LDD3: tiny_serial and tiny_tty

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Thank you Anuz,
this link helped a lot. At least now I can compile the modules.
Anyway I still couldn't get anything from the devices.
I'm going now to investigate further. Any help is appreciated

regards

- Luca


Anuz Pratap Singh Tomar wrote:
hi there,
Since API have changed so much, you need to change the code in accordance.
I was having some problem for all drivers i was compiling with my .23 kernel

there is this guy who have updated all drivers for .25 kernel at this link:
http://www.cs.fsu.edu/~baker/devices/lxr/source/2.6.25/ldd-examples/

Hope this helps

-Anuz

On Wed, Oct 22, 2008 at 4:01 PM, luca ellero <lroluk@xxxxxxxxx <mailto:lroluk@xxxxxxxxx>> wrote:

    Hi everybody,
    I'm trying to compile the examples of LDD3 with kernel 2.6.22.
    <http://2.6.22.>
    I get them from:

     http://www.oreilly.com.cn/codeexample/ldd3/

    I have some problems/questions regarding tiny_tty.c and
    tiny_serial.c (tty directory concerning chapter 18)

    1) Are they tty or uart drivers? What is the main difference between
    the two?
    2) I managed to compile tiny_serial.c, with some modifications to
    the source (which I've reported at the end of my e-mail), but when I
    "cat /dev/ttytiny" nothing happens (I would expect to get the 't'
    char every 2 sec). With some printk I can see that the tiny_timer is
    running fine but it seems that the characters aren't pushed to user
    space.
    3) I can't even compile tiny_tty.c. It seems the problem is in the
    change of the flip buffer implementation but I can find a good
    example of using this new code.

    Thank you very much
    regards
    Luca

    ---------------------------------------------------------

    /*
     * Tiny Serial driver
     *
     * Copyright (C) 2002-2004 Greg Kroah-Hartman (greg@xxxxxxxxx
    <mailto:greg@xxxxxxxxx>)
     *
     *      This program is free software; you can redistribute it
    and/or modify
     *      it under the terms of the GNU General Public License as
    published by
     *      the Free Software Foundation, version 2 of the License.
     *
     * This driver shows how to create a minimal serial driver.  It does
    not rely on
     * any backing hardware, but creates a timer that emulates data
    being received
     * from some kind of hardware.
     */

    #include <linux/kernel.h>
    #include <linux/errno.h>
    #include <linux/init.h>
    #include <linux/slab.h>
    #include <linux/tty.h>
    #include <linux/tty_flip.h>
    #include <linux/serial.h>
    #include <linux/serial_core.h>
    #include <linux/module.h>


    #define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@xxxxxxxxx
    <mailto:greg@xxxxxxxxx>>"
    #define DRIVER_DESC "Tiny serial driver"

    /* Module information */
    MODULE_AUTHOR( DRIVER_AUTHOR );
    MODULE_DESCRIPTION( DRIVER_DESC );
    MODULE_LICENSE("GPL");

    #define DELAY_TIME              HZ * 2  /* 2 seconds per character */
    #define TINY_DATA_CHARACTER     't'

    #define TINY_SERIAL_MAJOR       240     /* experimental range */
    #define TINY_SERIAL_MINORS      1       /* only have one minor */
    #define UART_NR                 1       /* only use one port */

    #define TINY_SERIAL_NAME        "ttytiny"

    #define MY_NAME                 TINY_SERIAL_NAME

    static struct timer_list *timer;

    static void tiny_stop_tx(struct uart_port *port)
    {
    }

    static void tiny_stop_rx(struct uart_port *port)
    {
    }

    static void tiny_enable_ms(struct uart_port *port)
    {
    }

    static void tiny_tx_chars(struct uart_port *port)
    {
           struct circ_buf *xmit = &port->info->xmit;
           int count;

           if (port->x_char) {
                   pr_debug("wrote %2x", port->x_char);
                   port->icount.tx++;
                   port->x_char = 0;
                   return;
           }
           if (uart_circ_empty(xmit) || uart_tx_stopped(port)) {
                   tiny_stop_tx(port);
                   return;
           }

           count = port->fifosize >> 1;
           do {
                   pr_debug("wrote %2x", xmit->buf[xmit->tail]);
                   xmit->tail = (xmit->tail + 1) & (UART_XMIT_SIZE - 1);
                   port->icount.tx++;
                   if (uart_circ_empty(xmit))
                           break;
           } while (--count > 0);

           if (uart_circ_chars_pending(xmit) < WAKEUP_CHARS)
                   uart_write_wakeup(port);

           if (uart_circ_empty(xmit))
                   tiny_stop_tx(port);
    }

    static void tiny_start_tx(struct uart_port *port)
    {
    }

    static void tiny_timer(unsigned long data)
    {
           struct uart_port *port;
           struct tty_struct *tty;


           port = (struct uart_port *)data;
           if (!port)
                   return;
           if (!port->info)
                   return;
           tty = port->info->tty;
           if (!tty)
                   return;

           /* add one character to the tty port */
           /* this doesn't actually push the data through unless
    tty->low_latency is set */
           tty_insert_flip_char(tty, TINY_DATA_CHARACTER, 0);

           tty_flip_buffer_push(tty);

           /* resubmit the timer again */
           timer->expires = jiffies + DELAY_TIME;
           add_timer(timer);

           /* see if we have any data to transmit */
           tiny_tx_chars(port);
    }

    static unsigned int tiny_tx_empty(struct uart_port *port)
    {
           return 0;
    }

    static unsigned int tiny_get_mctrl(struct uart_port *port)
    {
           return 0;
    }

    static void tiny_set_mctrl(struct uart_port *port, unsigned int mctrl)
    {
    }

    static void tiny_break_ctl(struct uart_port *port, int break_state)
    {
    }

    static void tiny_set_termios(struct uart_port *port,
                                struct ktermios *new, struct ktermios *old)
    {
    //      int baud, quot,
    int  cflag = new->c_cflag;
           /* get the byte size */
           switch (cflag & CSIZE) {
           case CS5:
                   printk(KERN_DEBUG " - data bits = 5\n");
                   break;
           case CS6:
                   printk(KERN_DEBUG " - data bits = 6\n");
                   break;
           case CS7:
                   printk(KERN_DEBUG " - data bits = 7\n");
                   break;
           default: // CS8
                   printk(KERN_DEBUG " - data bits = 8\n");
                   break;
           }

           /* determine the parity */
           if (cflag & PARENB)
                   if (cflag & PARODD)
                           pr_debug(" - parity = odd\n");
                   else
                           pr_debug(" - parity = even\n");
           else
                   pr_debug(" - parity = none\n");

           /* figure out the stop bits requested */
           if (cflag & CSTOPB)
                   pr_debug(" - stop bits = 2\n");
           else
                   pr_debug(" - stop bits = 1\n");

           /* figure out the flow control settings */
           if (cflag & CRTSCTS)
                   pr_debug(" - RTS/CTS is enabled\n");
           else
                   pr_debug(" - RTS/CTS is disabled\n");

           /* Set baud rate */
    //        baud = uart_get_baud_rate(port, new, old, 0,
    port->uartclk/16);
    //        quot = uart_get_divisor(port, baud);
//UART_PUT_DIV_LO(port, (quot & 0xff));
           //UART_PUT_DIV_HI(port, ((quot & 0xf00) >> 8));
    }

    static int tiny_startup(struct uart_port *port)
    {
           /* this is the first time this port is opened */
           /* do any hardware initialization needed here */

           /* create our timer and submit it */
           if (!timer) {
                   timer = kmalloc(sizeof(*timer), GFP_KERNEL);
                   if (!timer)
                           return -ENOMEM;
           }
           init_timer(timer);
           timer->data = (unsigned long)port;
           timer->expires = jiffies + DELAY_TIME;
           timer->function = tiny_timer;
           add_timer(timer);
           return 0;
    }

    static void tiny_shutdown(struct uart_port *port)
    {
           /* The port is being closed by the last user. */
           /* Do any hardware specific stuff here */

           /* shut down our timer */
           del_timer(timer);
    }

    static const char *tiny_type(struct uart_port *port)
    {
           return "tinytty";
    }

    static void tiny_release_port(struct uart_port *port)
    {

    }

    static int tiny_request_port(struct uart_port *port)
    {
           return 0;
    }

    static void tiny_config_port(struct uart_port *port, int flags)
    {
    }

    static int tiny_verify_port(struct uart_port *port, struct
    serial_struct *ser)
    {
           return 0;
    }

    static struct uart_ops tiny_ops = {
           .tx_empty       = tiny_tx_empty,
           .set_mctrl      = tiny_set_mctrl,
           .get_mctrl      = tiny_get_mctrl,
           .stop_tx        = tiny_stop_tx,
           .start_tx       = tiny_start_tx,
           .stop_rx        = tiny_stop_rx,
           .enable_ms      = tiny_enable_ms,
           .break_ctl      = tiny_break_ctl,
           .startup        = tiny_startup,
           .shutdown       = tiny_shutdown,
           .set_termios    = tiny_set_termios,
           .type           = tiny_type,
           .release_port   = tiny_release_port,
           .request_port   = tiny_request_port,
           .config_port    = tiny_config_port,
           .verify_port    = tiny_verify_port,
    };

    static struct uart_port tiny_port = {
           .ops            = &tiny_ops,
    };

    static struct uart_driver tiny_reg = {
           .owner          = THIS_MODULE,
           .driver_name    = TINY_SERIAL_NAME,
           .dev_name       = TINY_SERIAL_NAME,
           .major          = TINY_SERIAL_MAJOR,
           .minor          = TINY_SERIAL_MINORS,
           .nr             = UART_NR,
    };

    static int __init tiny_init(void)
    {
           int result;

           printk(KERN_INFO "Tiny serial driver loaded\n");

           result = uart_register_driver(&tiny_reg);
           if (result)
                   return result;

           tiny_port.type = PORT_16550A;


           result = uart_add_one_port(&tiny_reg, &tiny_port);
           if (result)
                   uart_unregister_driver(&tiny_reg);

           return result;
    }

    static void __exit tiny_exit(void)
    {
           uart_remove_one_port(&tiny_reg, &tiny_port);
           uart_unregister_driver(&tiny_reg);

    }

    module_init(tiny_init);
    module_exit(tiny_exit);


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