![Alan Cox](/assets/img/avatar_default.png)
The API and code have been through various bits of initial review by serial driver people but they definitely need to live somewhere for a while so the unconverted drivers can get knocked into shape, existing drivers that have been updated can be better tuned and bugs whacked out. This replaces the tty flip buffers with kmalloc objects in rings. In the normal situation for an IRQ driven serial port at typical speeds the behaviour is pretty much the same, two buffers end up allocated and the kernel cycles between them as before. When there are delays or at high speed we now behave far better as the buffer pool can grow a bit rather than lose characters. This also means that we can operate at higher speeds reliably. For drivers that receive characters in blocks (DMA based, USB and especially virtualisation) the layer allows a lot of driver specific code that works around the tty layer with private secondary queues to be removed. The IBM folks need this sort of layer, the smart serial port people do, the virtualisers do (because a virtualised tty typically operates at infinite speed rather than emulating 9600 baud). Finally many drivers had invalid and unsafe attempts to avoid buffer overflows by directly invoking tty methods extracted out of the innards of work queue structs. These are no longer needed and all go away. That fixes various random hangs with serial ports on overflow. The other change in here is to optimise the receive_room path that is used by some callers. It turns out that only one ldisc uses receive room except asa constant and it updates it far far less than the value is read. We thus make it a variable not a function call. I expect the code to contain bugs due to the size alone but I'll be watching and squashing them and feeding out new patches as it goes. Because the buffers now dynamically expand you should only run out of buffering when the kernel runs out of memory for real. That means a lot of the horrible hacks high performance drivers used to do just aren't needed any more. Description: tty_insert_flip_char is an old API and continues to work as before, as does tty_flip_buffer_push() [this is why many drivers dont need modification]. It does now also return the number of chars inserted There are also tty_buffer_request_room(tty, len) which asks for a buffer block of the length requested and returns the space found. This improves efficiency with hardware that knows how much to transfer. and tty_insert_flip_string_flags(tty, str, flags, len) to insert a string of characters and flags For a smart interface the usual code is len = tty_request_buffer_room(tty, amount_hardware_says); tty_insert_flip_string(tty, buffer_from_card, len); More description! At the moment tty buffers are attached directly to the tty. This is causing a lot of the problems related to tty layer locking, also problems at high speed and also with bursty data (such as occurs in virtualised environments) I'm working on ripping out the flip buffers and replacing them with a pool of dynamically allocated buffers. This allows both for old style "byte I/O" devices and also helps virtualisation and smart devices where large blocks of data suddenely materialise and need storing. So far so good. Lots of drivers reference tty->flip.*. Several of them also call directly and unsafely into function pointers it provides. This will all break. Most drivers can use tty_insert_flip_char which can be kept as an API but others need more. At the moment I've added the following interfaces, if people think more will be needed now is a good time to say int tty_buffer_request_room(tty, size) Try and ensure at least size bytes are available, returns actual room (may be zero). At the moment it just uses the flipbuf space but that will change. Repeated calls without characters being added are not cumulative. (ie if you call it with 1, 1, 1, and then 4 you'll have four characters of space. The other functions will also try and grow buffers in future but this will be a more efficient way when you know block sizes. int tty_insert_flip_char(tty, ch, flag) As before insert a character if there is room. Now returns 1 for success, 0 for failure. int tty_insert_flip_string(tty, str, len) Insert a block of non error characters. Returns the number inserted. int tty_prepare_flip_string(tty, strptr, len) Adjust the buffer to allow len characters to be added. Returns a buffer pointer in strptr and the length available. This allows for hardware that needs to use functions like insl or mencpy_fromio. Signed-off-by: Alan Cox <alan@redhat.com> Cc: Paul Fulghum <paulkf@microgate.com> Signed-off-by: Hirokazu Takata <takata@linux-m32r.org> Signed-off-by: Serge Hallyn <serue@us.ibm.com> Signed-off-by: Jeff Dike <jdike@addtoit.com> Signed-off-by: John Hawkes <hawkes@sgi.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com> Signed-off-by: Adrian Bunk <bunk@stusta.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
254 lines
6.1 KiB
C
254 lines
6.1 KiB
C
/*
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* Input device TTY line discipline
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*
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* Copyright (c) 1999-2002 Vojtech Pavlik
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*
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* This is a module that converts a tty line into a much simpler
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* 'serial io port' abstraction that the input device drivers use.
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*/
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/*
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* This program is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 as published by
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* the Free Software Foundation.
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*/
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#include <asm/uaccess.h>
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#include <linux/kernel.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/serio.h>
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#include <linux/tty.h>
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MODULE_AUTHOR("Vojtech Pavlik <vojtech@ucw.cz>");
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MODULE_DESCRIPTION("Input device TTY line discipline");
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MODULE_LICENSE("GPL");
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MODULE_ALIAS_LDISC(N_MOUSE);
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#define SERPORT_BUSY 1
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#define SERPORT_ACTIVE 2
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#define SERPORT_DEAD 3
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struct serport {
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struct tty_struct *tty;
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wait_queue_head_t wait;
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struct serio *serio;
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struct serio_device_id id;
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spinlock_t lock;
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unsigned long flags;
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};
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/*
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* Callback functions from the serio code.
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*/
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static int serport_serio_write(struct serio *serio, unsigned char data)
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{
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struct serport *serport = serio->port_data;
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return -(serport->tty->driver->write(serport->tty, &data, 1) != 1);
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}
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static int serport_serio_open(struct serio *serio)
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{
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struct serport *serport = serio->port_data;
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unsigned long flags;
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spin_lock_irqsave(&serport->lock, flags);
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set_bit(SERPORT_ACTIVE, &serport->flags);
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spin_unlock_irqrestore(&serport->lock, flags);
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return 0;
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}
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static void serport_serio_close(struct serio *serio)
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{
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struct serport *serport = serio->port_data;
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unsigned long flags;
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spin_lock_irqsave(&serport->lock, flags);
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clear_bit(SERPORT_ACTIVE, &serport->flags);
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set_bit(SERPORT_DEAD, &serport->flags);
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spin_unlock_irqrestore(&serport->lock, flags);
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wake_up_interruptible(&serport->wait);
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}
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/*
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* serport_ldisc_open() is the routine that is called upon setting our line
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* discipline on a tty. It prepares the serio struct.
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*/
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static int serport_ldisc_open(struct tty_struct *tty)
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{
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struct serport *serport;
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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serport = kzalloc(sizeof(struct serport), GFP_KERNEL);
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if (!serport)
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return -ENOMEM;
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serport->tty = tty;
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spin_lock_init(&serport->lock);
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init_waitqueue_head(&serport->wait);
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tty->disc_data = serport;
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tty->receive_room = 256;
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set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
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return 0;
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}
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/*
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* serport_ldisc_close() is the opposite of serport_ldisc_open()
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*/
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static void serport_ldisc_close(struct tty_struct *tty)
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{
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struct serport *serport = (struct serport *) tty->disc_data;
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kfree(serport);
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}
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/*
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* serport_ldisc_receive() is called by the low level tty driver when characters
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* are ready for us. We forward the characters, one by one to the 'interrupt'
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* routine.
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*
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* FIXME: We should get pt_regs from the tty layer and forward them to
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* serio_interrupt here.
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*/
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static void serport_ldisc_receive(struct tty_struct *tty, const unsigned char *cp, char *fp, int count)
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{
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struct serport *serport = (struct serport*) tty->disc_data;
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unsigned long flags;
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int i;
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spin_lock_irqsave(&serport->lock, flags);
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if (!test_bit(SERPORT_ACTIVE, &serport->flags))
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goto out;
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for (i = 0; i < count; i++)
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serio_interrupt(serport->serio, cp[i], 0, NULL);
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out:
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spin_unlock_irqrestore(&serport->lock, flags);
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}
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/*
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* serport_ldisc_read() just waits indefinitely if everything goes well.
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* However, when the serio driver closes the serio port, it finishes,
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* returning 0 characters.
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*/
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static ssize_t serport_ldisc_read(struct tty_struct * tty, struct file * file, unsigned char __user * buf, size_t nr)
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{
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struct serport *serport = (struct serport*) tty->disc_data;
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struct serio *serio;
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char name[64];
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if (test_and_set_bit(SERPORT_BUSY, &serport->flags))
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return -EBUSY;
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serport->serio = serio = kzalloc(sizeof(struct serio), GFP_KERNEL);
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if (!serio)
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return -ENOMEM;
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strlcpy(serio->name, "Serial port", sizeof(serio->name));
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snprintf(serio->phys, sizeof(serio->phys), "%s/serio0", tty_name(tty, name));
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serio->id = serport->id;
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serio->id.type = SERIO_RS232;
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serio->write = serport_serio_write;
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serio->open = serport_serio_open;
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serio->close = serport_serio_close;
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serio->port_data = serport;
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serio_register_port(serport->serio);
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printk(KERN_INFO "serio: Serial port %s\n", tty_name(tty, name));
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wait_event_interruptible(serport->wait, test_bit(SERPORT_DEAD, &serport->flags));
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serio_unregister_port(serport->serio);
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serport->serio = NULL;
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clear_bit(SERPORT_DEAD, &serport->flags);
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clear_bit(SERPORT_BUSY, &serport->flags);
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return 0;
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}
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/*
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* serport_ldisc_ioctl() allows to set the port protocol, and device ID
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*/
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static int serport_ldisc_ioctl(struct tty_struct * tty, struct file * file, unsigned int cmd, unsigned long arg)
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{
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struct serport *serport = (struct serport*) tty->disc_data;
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unsigned long type;
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if (cmd == SPIOCSTYPE) {
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if (get_user(type, (unsigned long __user *) arg))
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return -EFAULT;
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serport->id.proto = type & 0x000000ff;
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serport->id.id = (type & 0x0000ff00) >> 8;
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serport->id.extra = (type & 0x00ff0000) >> 16;
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return 0;
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}
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return -EINVAL;
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}
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static void serport_ldisc_write_wakeup(struct tty_struct * tty)
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{
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struct serport *serport = (struct serport *) tty->disc_data;
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unsigned long flags;
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spin_lock_irqsave(&serport->lock, flags);
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if (test_bit(SERPORT_ACTIVE, &serport->flags))
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serio_drv_write_wakeup(serport->serio);
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spin_unlock_irqrestore(&serport->lock, flags);
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}
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/*
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* The line discipline structure.
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*/
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static struct tty_ldisc serport_ldisc = {
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.owner = THIS_MODULE,
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.name = "input",
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.open = serport_ldisc_open,
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.close = serport_ldisc_close,
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.read = serport_ldisc_read,
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.ioctl = serport_ldisc_ioctl,
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.receive_buf = serport_ldisc_receive,
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.write_wakeup = serport_ldisc_write_wakeup
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};
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/*
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* The functions for insering/removing us as a module.
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*/
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static int __init serport_init(void)
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{
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int retval;
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retval = tty_register_ldisc(N_MOUSE, &serport_ldisc);
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if (retval)
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printk(KERN_ERR "serport.c: Error registering line discipline.\n");
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return retval;
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}
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static void __exit serport_exit(void)
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{
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tty_unregister_ldisc(N_MOUSE);
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}
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module_init(serport_init);
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module_exit(serport_exit);
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