/* * Simulated Serial Driver (fake serial) * * This driver is mostly used for bringup purposes and will go away. * It has a strong dependency on the system console. All outputs * are rerouted to the same facility as the one used by printk which, in our * case means sys_sim.c console (goes via the simulator). The code hereafter * is completely leveraged from the serial.c driver. * * Copyright (C) 1999-2000, 2002-2003 Hewlett-Packard Co * Stephane Eranian * David Mosberger-Tang * * 02/04/00 D. Mosberger Merged in serial.c bug fixes in rs_close(). * 02/25/00 D. Mosberger Synced up with 2.3.99pre-5 version of serial.c. * 07/30/02 D. Mosberger Replace sti()/cli() with explicit spinlocks & local irq masking */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #undef SIMSERIAL_DEBUG /* define this to get some debug information */ #define KEYBOARD_INTR 3 /* must match with simulator! */ #define NR_PORTS 1 /* only one port for now */ #define IRQ_T(info) ((info->flags & ASYNC_SHARE_IRQ) ? IRQF_SHARED : IRQF_DISABLED) #define SSC_GETCHAR 21 extern long ia64_ssc (long, long, long, long, int); extern void ia64_ssc_connect_irq (long intr, long irq); static char *serial_name = "SimSerial driver"; static char *serial_version = "0.6"; /* * This has been extracted from asm/serial.h. We need one eventually but * I don't know exactly what we're going to put in it so just fake one * for now. */ #define BASE_BAUD ( 1843200 / 16 ) #define STD_COM_FLAGS (ASYNC_BOOT_AUTOCONF | ASYNC_SKIP_TEST) /* * Most of the values here are meaningless to this particular driver. * However some values must be preserved for the code (leveraged from serial.c * to work correctly). * port must not be 0 * type must not be UNKNOWN * So I picked arbitrary (guess from where?) values instead */ static struct serial_state rs_table[NR_PORTS]={ /* UART CLK PORT IRQ FLAGS */ { BASE_BAUD, 0x3F8, 0, STD_COM_FLAGS, PORT_16550 } /* ttyS0 */ }; /* * Just for the fun of it ! */ static struct serial_uart_config uart_config[] = { { "unknown", 1, 0 }, { "8250", 1, 0 }, { "16450", 1, 0 }, { "16550", 1, 0 }, { "16550A", 16, UART_CLEAR_FIFO | UART_USE_FIFO }, { "cirrus", 1, 0 }, { "ST16650", 1, UART_CLEAR_FIFO | UART_STARTECH }, { "ST16650V2", 32, UART_CLEAR_FIFO | UART_USE_FIFO | UART_STARTECH }, { "TI16750", 64, UART_CLEAR_FIFO | UART_USE_FIFO}, { NULL, 0} }; struct tty_driver *hp_simserial_driver; static struct async_struct *IRQ_ports[NR_IRQS]; static struct console *console; static unsigned char *tmp_buf; extern struct console *console_drivers; /* from kernel/printk.c */ /* * ------------------------------------------------------------ * rs_stop() and rs_start() * * This routines are called before setting or resetting tty->stopped. * They enable or disable transmitter interrupts, as necessary. * ------------------------------------------------------------ */ static void rs_stop(struct tty_struct *tty) { #ifdef SIMSERIAL_DEBUG printk("rs_stop: tty->stopped=%d tty->hw_stopped=%d tty->flow_stopped=%d\n", tty->stopped, tty->hw_stopped, tty->flow_stopped); #endif } static void rs_start(struct tty_struct *tty) { #ifdef SIMSERIAL_DEBUG printk("rs_start: tty->stopped=%d tty->hw_stopped=%d tty->flow_stopped=%d\n", tty->stopped, tty->hw_stopped, tty->flow_stopped); #endif } static void receive_chars(struct tty_struct *tty) { unsigned char ch; static unsigned char seen_esc = 0; while ( (ch = ia64_ssc(0, 0, 0, 0, SSC_GETCHAR)) ) { if ( ch == 27 && seen_esc == 0 ) { seen_esc = 1; continue; } else { if ( seen_esc==1 && ch == 'O' ) { seen_esc = 2; continue; } else if ( seen_esc == 2 ) { if ( ch == 'P' ) /* F1 */ show_state(); #ifdef CONFIG_MAGIC_SYSRQ if ( ch == 'S' ) { /* F4 */ do ch = ia64_ssc(0, 0, 0, 0, SSC_GETCHAR); while (!ch); handle_sysrq(ch); } #endif seen_esc = 0; continue; } } seen_esc = 0; if (tty_insert_flip_char(tty, ch, TTY_NORMAL) == 0) break; } tty_flip_buffer_push(tty); } /* * This is the serial driver's interrupt routine for a single port */ static irqreturn_t rs_interrupt_single(int irq, void *dev_id) { struct async_struct * info; /* * I don't know exactly why they don't use the dev_id opaque data * pointer instead of this extra lookup table */ info = IRQ_ports[irq]; if (!info || !info->tty) { printk(KERN_INFO "simrs_interrupt_single: info|tty=0 info=%p problem\n", info); return IRQ_NONE; } /* * pretty simple in our case, because we only get interrupts * on inbound traffic */ receive_chars(info->tty); return IRQ_HANDLED; } /* * ------------------------------------------------------------------- * Here ends the serial interrupt routines. * ------------------------------------------------------------------- */ static int rs_put_char(struct tty_struct *tty, unsigned char ch) { struct async_struct *info = (struct async_struct *)tty->driver_data; unsigned long flags; if (!tty || !info->xmit.buf) return 0; local_irq_save(flags); if (CIRC_SPACE(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE) == 0) { local_irq_restore(flags); return 0; } info->xmit.buf[info->xmit.head] = ch; info->xmit.head = (info->xmit.head + 1) & (SERIAL_XMIT_SIZE-1); local_irq_restore(flags); return 1; } static void transmit_chars(struct async_struct *info, int *intr_done) { int count; unsigned long flags; local_irq_save(flags); if (info->x_char) { char c = info->x_char; console->write(console, &c, 1); info->state->icount.tx++; info->x_char = 0; goto out; } if (info->xmit.head == info->xmit.tail || info->tty->stopped || info->tty->hw_stopped) { #ifdef SIMSERIAL_DEBUG printk("transmit_chars: head=%d, tail=%d, stopped=%d\n", info->xmit.head, info->xmit.tail, info->tty->stopped); #endif goto out; } /* * We removed the loop and try to do it in to chunks. We need * 2 operations maximum because it's a ring buffer. * * First from current to tail if possible. * Then from the beginning of the buffer until necessary */ count = min(CIRC_CNT(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE), SERIAL_XMIT_SIZE - info->xmit.tail); console->write(console, info->xmit.buf+info->xmit.tail, count); info->xmit.tail = (info->xmit.tail+count) & (SERIAL_XMIT_SIZE-1); /* * We have more at the beginning of the buffer */ count = CIRC_CNT(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE); if (count) { console->write(console, info->xmit.buf, count); info->xmit.tail += count; } out: local_irq_restore(flags); } static void rs_flush_chars(struct tty_struct *tty) { struct async_struct *info = (struct async_struct *)tty->driver_data; if (info->xmit.head == info->xmit.tail || tty->stopped || tty->hw_stopped || !info->xmit.buf) return; transmit_chars(info, NULL); } static int rs_write(struct tty_struct * tty, const unsigned char *buf, int count) { int c, ret = 0; struct async_struct *info = (struct async_struct *)tty->driver_data; unsigned long flags; if (!tty || !info->xmit.buf || !tmp_buf) return 0; local_irq_save(flags); while (1) { c = CIRC_SPACE_TO_END(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE); if (count < c) c = count; if (c <= 0) { break; } memcpy(info->xmit.buf + info->xmit.head, buf, c); info->xmit.head = ((info->xmit.head + c) & (SERIAL_XMIT_SIZE-1)); buf += c; count -= c; ret += c; } local_irq_restore(flags); /* * Hey, we transmit directly from here in our case */ if (CIRC_CNT(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE) && !tty->stopped && !tty->hw_stopped) { transmit_chars(info, NULL); } return ret; } static int rs_write_room(struct tty_struct *tty) { struct async_struct *info = (struct async_struct *)tty->driver_data; return CIRC_SPACE(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE); } static int rs_chars_in_buffer(struct tty_struct *tty) { struct async_struct *info = (struct async_struct *)tty->driver_data; return CIRC_CNT(info->xmit.head, info->xmit.tail, SERIAL_XMIT_SIZE); } static void rs_flush_buffer(struct tty_struct *tty) { struct async_struct *info = (struct async_struct *)tty->driver_data; unsigned long flags; local_irq_save(flags); info->xmit.head = info->xmit.tail = 0; local_irq_restore(flags); tty_wakeup(tty); } /* * This function is used to send a high-priority XON/XOFF character to * the device */ static void rs_send_xchar(struct tty_struct *tty, char ch) { struct async_struct *info = (struct async_struct *)tty->driver_data; info->x_char = ch; if (ch) { /* * I guess we could call console->write() directly but * let's do that for now. */ transmit_chars(info, NULL); } } /* * ------------------------------------------------------------ * rs_throttle() * * This routine is called by the upper-layer tty layer to signal that * incoming characters should be throttled. * ------------------------------------------------------------ */ static void rs_throttle(struct tty_struct * tty) { if (I_IXOFF(tty)) rs_send_xchar(tty, STOP_CHAR(tty)); printk(KERN_INFO "simrs_throttle called\n"); } static void rs_unthrottle(struct tty_struct * tty) { struct async_struct *info = (struct async_struct *)tty->driver_data; if (I_IXOFF(tty)) { if (info->x_char) info->x_char = 0; else rs_send_xchar(tty, START_CHAR(tty)); } printk(KERN_INFO "simrs_unthrottle called\n"); } static int rs_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg) { if ((cmd != TIOCGSERIAL) && (cmd != TIOCSSERIAL) && (cmd != TIOCSERCONFIG) && (cmd != TIOCSERGSTRUCT) && (cmd != TIOCMIWAIT)) { if (tty->flags & (1 << TTY_IO_ERROR)) return -EIO; } switch (cmd) { case TIOCGSERIAL: printk(KERN_INFO "simrs_ioctl TIOCGSERIAL called\n"); return 0; case TIOCSSERIAL: printk(KERN_INFO "simrs_ioctl TIOCSSERIAL called\n"); return 0; case TIOCSERCONFIG: printk(KERN_INFO "rs_ioctl: TIOCSERCONFIG called\n"); return -EINVAL; case TIOCSERGETLSR: /* Get line status register */ printk(KERN_INFO "rs_ioctl: TIOCSERGETLSR called\n"); return -EINVAL; case TIOCSERGSTRUCT: printk(KERN_INFO "rs_ioctl: TIOCSERGSTRUCT called\n"); #if 0 if (copy_to_user((struct async_struct *) arg, info, sizeof(struct async_struct))) return -EFAULT; #endif return 0; /* * Wait for any of the 4 modem inputs (DCD,RI,DSR,CTS) to change * - mask passed in arg for lines of interest * (use |'ed TIOCM_RNG/DSR/CD/CTS for masking) * Caller should use TIOCGICOUNT to see which one it was */ case TIOCMIWAIT: printk(KERN_INFO "rs_ioctl: TIOCMIWAIT: called\n"); return 0; case TIOCSERGWILD: case TIOCSERSWILD: /* "setserial -W" is called in Debian boot */ printk (KERN_INFO "TIOCSER?WILD ioctl obsolete, ignored.\n"); return 0; default: return -ENOIOCTLCMD; } return 0; } #define RELEVANT_IFLAG(iflag) (iflag & (IGNBRK|BRKINT|IGNPAR|PARMRK|INPCK)) static void rs_set_termios(struct tty_struct *tty, struct ktermios *old_termios) { /* Handle turning off CRTSCTS */ if ((old_termios->c_cflag & CRTSCTS) && !(tty->termios->c_cflag & CRTSCTS)) { tty->hw_stopped = 0; rs_start(tty); } } /* * This routine will shutdown a serial port; interrupts are disabled, and * DTR is dropped if the hangup on close termio flag is on. */ static void shutdown(struct async_struct * info) { unsigned long flags; struct serial_state *state; int retval; if (!(info->flags & ASYNC_INITIALIZED)) return; state = info->state; #ifdef SIMSERIAL_DEBUG printk("Shutting down serial port %d (irq %d)....", info->line, state->irq); #endif local_irq_save(flags); { /* * First unlink the serial port from the IRQ chain... */ if (info->next_port) info->next_port->prev_port = info->prev_port; if (info->prev_port) info->prev_port->next_port = info->next_port; else IRQ_ports[state->irq] = info->next_port; /* * Free the IRQ, if necessary */ if (state->irq && (!IRQ_ports[state->irq] || !IRQ_ports[state->irq]->next_port)) { if (IRQ_ports[state->irq]) { free_irq(state->irq, NULL); retval = request_irq(state->irq, rs_interrupt_single, IRQ_T(info), "serial", NULL); if (retval) printk(KERN_ERR "serial shutdown: request_irq: error %d" " Couldn't reacquire IRQ.\n", retval); } else free_irq(state->irq, NULL); } if (info->xmit.buf) { free_page((unsigned long) info->xmit.buf); info->xmit.buf = NULL; } if (info->tty) set_bit(TTY_IO_ERROR, &info->tty->flags); info->flags &= ~ASYNC_INITIALIZED; } local_irq_restore(flags); } /* * ------------------------------------------------------------ * rs_close() * * This routine is called when the serial port gets closed. First, we * wait for the last remaining data to be sent. Then, we unlink its * async structure from the interrupt chain if necessary, and we free * that IRQ if nothing is left in the chain. * ------------------------------------------------------------ */ static void rs_close(struct tty_struct *tty, struct file * filp) { struct async_struct * info = (struct async_struct *)tty->driver_data; struct serial_state *state; unsigned long flags; if (!info ) return; state = info->state; local_irq_save(flags); if (tty_hung_up_p(filp)) { #ifdef SIMSERIAL_DEBUG printk("rs_close: hung_up\n"); #endif local_irq_restore(flags); return; } #ifdef SIMSERIAL_DEBUG printk("rs_close ttys%d, count = %d\n", info->line, state->count); #endif if ((tty->count == 1) && (state->count != 1)) { /* * Uh, oh. tty->count is 1, which means that the tty * structure will be freed. state->count should always * be one in these conditions. If it's greater than * one, we've got real problems, since it means the * serial port won't be shutdown. */ printk(KERN_ERR "rs_close: bad serial port count; tty->count is 1, " "state->count is %d\n", state->count); state->count = 1; } if (--state->count < 0) { printk(KERN_ERR "rs_close: bad serial port count for ttys%d: %d\n", info->line, state->count); state->count = 0; } if (state->count) { local_irq_restore(flags); return; } info->flags |= ASYNC_CLOSING; local_irq_restore(flags); /* * Now we wait for the transmit buffer to clear; and we notify * the line discipline to only process XON/XOFF characters. */ shutdown(info); rs_flush_buffer(tty); tty_ldisc_flush(tty); info->event = 0; info->tty = NULL; if (info->blocked_open) { if (info->close_delay) schedule_timeout_interruptible(info->close_delay); wake_up_interruptible(&info->open_wait); } info->flags &= ~(ASYNC_NORMAL_ACTIVE|ASYNC_CLOSING); wake_up_interruptible(&info->close_wait); } /* * rs_wait_until_sent() --- wait until the transmitter is empty */ static void rs_wait_until_sent(struct tty_struct *tty, int timeout) { } /* * rs_hangup() --- called by tty_hangup() when a hangup is signaled. */ static void rs_hangup(struct tty_struct *tty) { struct async_struct * info = (struct async_struct *)tty->driver_data; struct serial_state *state = info->state; #ifdef SIMSERIAL_DEBUG printk("rs_hangup: called\n"); #endif state = info->state; rs_flush_buffer(tty); if (info->flags & ASYNC_CLOSING) return; shutdown(info); info->event = 0; state->count = 0; info->flags &= ~ASYNC_NORMAL_ACTIVE; info->tty = NULL; wake_up_interruptible(&info->open_wait); } static int get_async_struct(int line, struct async_struct **ret_info) { struct async_struct *info; struct serial_state *sstate; sstate = rs_table + line; sstate->count++; if (sstate->info) { *ret_info = sstate->info; return 0; } info = kzalloc(sizeof(struct async_struct), GFP_KERNEL); if (!info) { sstate->count--; return -ENOMEM; } init_waitqueue_head(&info->open_wait); init_waitqueue_head(&info->close_wait); info->port = sstate->port; info->flags = sstate->flags; info->xmit_fifo_size = sstate->xmit_fifo_size; info->line = line; info->state = sstate; if (sstate->info) { kfree(info); *ret_info = sstate->info; return 0; } *ret_info = sstate->info = info; return 0; } static int startup(struct async_struct *info) { unsigned long flags; int retval=0; irq_handler_t handler; struct serial_state *state= info->state; unsigned long page; page = get_zeroed_page(GFP_KERNEL); if (!page) return -ENOMEM; local_irq_save(flags); if (info->flags & ASYNC_INITIALIZED) { free_page(page); goto errout; } if (!state->port || !state->type) { if (info->tty) set_bit(TTY_IO_ERROR, &info->tty->flags); free_page(page); goto errout; } if (info->xmit.buf) free_page(page); else info->xmit.buf = (unsigned char *) page; #ifdef SIMSERIAL_DEBUG printk("startup: ttys%d (irq %d)...", info->line, state->irq); #endif /* * Allocate the IRQ if necessary */ if (state->irq && (!IRQ_ports[state->irq] || !IRQ_ports[state->irq]->next_port)) { if (IRQ_ports[state->irq]) { retval = -EBUSY; goto errout; } else handler = rs_interrupt_single; retval = request_irq(state->irq, handler, IRQ_T(info), "simserial", NULL); if (retval) { if (capable(CAP_SYS_ADMIN)) { if (info->tty) set_bit(TTY_IO_ERROR, &info->tty->flags); retval = 0; } goto errout; } } /* * Insert serial port into IRQ chain. */ info->prev_port = NULL; info->next_port = IRQ_ports[state->irq]; if (info->next_port) info->next_port->prev_port = info; IRQ_ports[state->irq] = info; if (info->tty) clear_bit(TTY_IO_ERROR, &info->tty->flags); info->xmit.head = info->xmit.tail = 0; #if 0 /* * Set up serial timers... */ timer_table[RS_TIMER].expires = jiffies + 2*HZ/100; timer_active |= 1 << RS_TIMER; #endif /* * Set up the tty->alt_speed kludge */ if (info->tty) { if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_HI) info->tty->alt_speed = 57600; if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_VHI) info->tty->alt_speed = 115200; if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_SHI) info->tty->alt_speed = 230400; if ((info->flags & ASYNC_SPD_MASK) == ASYNC_SPD_WARP) info->tty->alt_speed = 460800; } info->flags |= ASYNC_INITIALIZED; local_irq_restore(flags); return 0; errout: local_irq_restore(flags); return retval; } /* * This routine is called whenever a serial port is opened. It * enables interrupts for a serial port, linking in its async structure into * the IRQ chain. It also performs the serial-specific * initialization for the tty structure. */ static int rs_open(struct tty_struct *tty, struct file * filp) { struct async_struct *info; int retval; unsigned long page; retval = get_async_struct(tty->index, &info); if (retval) return retval; tty->driver_data = info; info->tty = tty; #ifdef SIMSERIAL_DEBUG printk("rs_open %s, count = %d\n", tty->name, info->state->count); #endif info->tty->low_latency = (info->flags & ASYNC_LOW_LATENCY) ? 1 : 0; if (!tmp_buf) { page = get_zeroed_page(GFP_KERNEL); if (!page) return -ENOMEM; if (tmp_buf) free_page(page); else tmp_buf = (unsigned char *) page; } /* * If the port is the middle of closing, bail out now */ if (tty_hung_up_p(filp) || (info->flags & ASYNC_CLOSING)) { if (info->flags & ASYNC_CLOSING) interruptible_sleep_on(&info->close_wait); #ifdef SERIAL_DO_RESTART return ((info->flags & ASYNC_HUP_NOTIFY) ? -EAGAIN : -ERESTARTSYS); #else return -EAGAIN; #endif } /* * Start up serial port */ retval = startup(info); if (retval) { return retval; } /* * figure out which console to use (should be one already) */ console = console_drivers; while (console) { if ((console->flags & CON_ENABLED) && console->write) break; console = console->next; } #ifdef SIMSERIAL_DEBUG printk("rs_open ttys%d successful\n", info->line); #endif return 0; } /* * /proc fs routines.... */ static inline void line_info(struct seq_file *m, struct serial_state *state) { seq_printf(m, "%d: uart:%s port:%lX irq:%d\n", state->line, uart_config[state->type].name, state->port, state->irq); } static int rs_proc_show(struct seq_file *m, void *v) { int i; seq_printf(m, "simserinfo:1.0 driver:%s\n", serial_version); for (i = 0; i < NR_PORTS; i++) line_info(m, &rs_table[i]); return 0; } static int rs_proc_open(struct inode *inode, struct file *file) { return single_open(file, rs_proc_show, NULL); } static const struct file_operations rs_proc_fops = { .owner = THIS_MODULE, .open = rs_proc_open, .read = seq_read, .llseek = seq_lseek, .release = single_release, }; /* * --------------------------------------------------------------------- * rs_init() and friends * * rs_init() is called at boot-time to initialize the serial driver. * --------------------------------------------------------------------- */ /* * This routine prints out the appropriate serial driver version * number, and identifies which options were configured into this * driver. */ static inline void show_serial_version(void) { printk(KERN_INFO "%s version %s with", serial_name, serial_version); printk(KERN_INFO " no serial options enabled\n"); } static const struct tty_operations hp_ops = { .open = rs_open, .close = rs_close, .write = rs_write, .put_char = rs_put_char, .flush_chars = rs_flush_chars, .write_room = rs_write_room, .chars_in_buffer = rs_chars_in_buffer, .flush_buffer = rs_flush_buffer, .ioctl = rs_ioctl, .throttle = rs_throttle, .unthrottle = rs_unthrottle, .send_xchar = rs_send_xchar, .set_termios = rs_set_termios, .stop = rs_stop, .start = rs_start, .hangup = rs_hangup, .wait_until_sent = rs_wait_until_sent, .proc_fops = &rs_proc_fops, }; /* * The serial driver boot-time initialization code! */ static int __init simrs_init (void) { int i, rc; struct serial_state *state; if (!ia64_platform_is("hpsim")) return -ENODEV; hp_simserial_driver = alloc_tty_driver(NR_PORTS); if (!hp_simserial_driver) return -ENOMEM; show_serial_version(); /* Initialize the tty_driver structure */ hp_simserial_driver->driver_name = "simserial"; hp_simserial_driver->name = "ttyS"; hp_simserial_driver->major = TTY_MAJOR; hp_simserial_driver->minor_start = 64; hp_simserial_driver->type = TTY_DRIVER_TYPE_SERIAL; hp_simserial_driver->subtype = SERIAL_TYPE_NORMAL; hp_simserial_driver->init_termios = tty_std_termios; hp_simserial_driver->init_termios.c_cflag = B9600 | CS8 | CREAD | HUPCL | CLOCAL; hp_simserial_driver->flags = TTY_DRIVER_REAL_RAW; tty_set_operations(hp_simserial_driver, &hp_ops); /* * Let's have a little bit of fun ! */ for (i = 0, state = rs_table; i < NR_PORTS; i++,state++) { if (state->type == PORT_UNKNOWN) continue; if (!state->irq) { if ((rc = assign_irq_vector(AUTO_ASSIGN)) < 0) panic("%s: out of interrupt vectors!\n", __func__); state->irq = rc; ia64_ssc_connect_irq(KEYBOARD_INTR, state->irq); } printk(KERN_INFO "ttyS%d at 0x%04lx (irq = %d) is a %s\n", state->line, state->port, state->irq, uart_config[state->type].name); } if (tty_register_driver(hp_simserial_driver)) panic("Couldn't register simserial driver\n"); return 0; } #ifndef MODULE __initcall(simrs_init); #endif