Re: [RFC/RFT] Raw access to serio ports (1/2)

Dmitry Torokhov
2004-06-03T05:46:26Z

Ok, new version:

- fixed return value logic in rawdev_write,
- rawdev_read and rawdev_write arguments marked with __user,
- some comments sprinkled around ;)

===================================================================

ChangeSet@1.1840, 2004-06-02 22:31:17-05:00, dtor_core@ameritech.net
Input: Add rawdev driver that binds to serio ports marked as 'raw'
and provides unobstructed access to the underlying serio port
via a char device. The driver tries to register char device
10,1 (/dev/psaux) first and if it fails goes for dynamically
allocated minor.

Signed-off-by: Dmitry Torokhov <dtor@mail.ru>

drivers/input/misc/Kconfig | 12 +
drivers/input/misc/Makefile | 1
drivers/input/misc/rawdev.c | 422 ++++++++++++++++++++++++++++++++++++++++++++
include/linux/serio.h | 1
4 files changed, 436 insertions(+)

===================================================================

diff -Nru a/drivers/input/misc/Kconfig b/drivers/input/misc/Kconfig
--- a/drivers/input/misc/Kconfig 2004-06-02 23:08:36 -05:00
+++ b/drivers/input/misc/Kconfig 2004-06-02 23:08:36 -05:00
@@ -54,3 +54,15 @@
To compile this driver as a module, choose M here: the
module will be called uinput.

+config INPUT_RAWDEV
+ tristate "Raw access to serio ports"
+ depends on INPUT && INPUT_MISC
+ help
+ Say Y here if you want to have raw access to serio ports, such as
+ AUX ports on i8042 keyboard controller. Each serio port that is
+ marked as providing raw access will be accessible via a char device
+ with major 10 and dynamically allocated minor (it will first try
+ allocating minor 1 historically corresponding to /dev/psaux).
+
+ To compile this driver as a module, choose M here: the
+ module will be called rawdev.
diff -Nru a/drivers/input/misc/Makefile b/drivers/input/misc/Makefile
--- a/drivers/input/misc/Makefile 2004-06-02 23:08:36 -05:00
+++ b/drivers/input/misc/Makefile 2004-06-02 23:08:36 -05:00
@@ -9,3 +9,4 @@
obj-$(CONFIG_INPUT_M68K_BEEP) += m68kspkr.o
obj-$(CONFIG_INPUT_98SPKR) += 98spkr.o
obj-$(CONFIG_INPUT_UINPUT) += uinput.o
+obj-$(CONFIG_INPUT_RAWDEV) += rawdev.o
diff -Nru a/drivers/input/misc/rawdev.c b/drivers/input/misc/rawdev.c
--- /dev/null Wed Dec 31 16:00:00 196900
+++ b/drivers/input/misc/rawdev.c 2004-06-02 23:08:36 -05:00
@@ -0,0 +1,422 @@
+/*
+ * Raw serio device providing access to a raw byte stream from underlying
+ * serio port. Closely emulates behavior of pre-2.6 /dev/psaux device
+ *
+ * Copyright (c) 2004 Dmitry Torokhov
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/module.h>
+#include <linux/serio.h>
+#include <linux/init.h>
+#include <linux/major.h>
+#include <linux/device.h>
+#include <linux/devfs_fs_kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/wait.h>
+
+MODULE_AUTHOR("Dmitry Torokhov <dtor@mail.ru>");
+MODULE_DESCRIPTION("Raw serio driver");
+MODULE_LICENSE("GPL");
+
+#define RAWDEV_QUEUE_LEN 64
+struct rawdev {
+ unsigned char queue[RAWDEV_QUEUE_LEN];
+ unsigned int tail, head;
+ spinlock_t lock; /* protects queue, tail and head */
+
+ char name[16];
+ unsigned int refcnt;
+ struct serio *serio;
+ struct miscdevice dev;
+ wait_queue_head_t wait;
+ struct list_head list;
+ struct list_head node;
+};
+
+struct rawdev_list {
+ struct fasync_struct *fasync;
+ struct rawdev *rawdev;
+ struct list_head node;
+};
+
+static DECLARE_MUTEX(rawdev_sem); /* protects rawdev_list, rawdev_no and rawdev->serio */
+static LIST_HEAD(rawdev_list);
+static unsigned int rawdev_no;
+
+
+/*********************************************************************
+ * Interface with userspace (file operations) *
+ *********************************************************************/
+
+static int rawdev_fasync(int fd, struct file *file, int on)
+{
+ struct rawdev_list *list = file->private_data;
+ int retval;
+
+ retval = fasync_helper(fd, file, on, &list->fasync);
+ return retval < 0 ? retval : 0;
+}
+
+/*
+ * Try to locate rawdev corresponding to a given minor.
+ * rawdev_sem has to be taken before calling rawdev_locate.
+ */
+static struct rawdev *rawdev_locate(int minor)
+{
+ struct rawdev *rawdev;
+
+ list_for_each_entry(rawdev, &rawdev_list, node) {
+ if (rawdev->dev.minor == minor)
+ return rawdev;
+ }
+
+ return NULL;
+}
+
+static int rawdev_open(struct inode *inode, struct file *file)
+{
+ struct rawdev *rawdev;
+ struct rawdev_list *list;
+ int retval;
+
+ retval = down_interruptible(&rawdev_sem);
+ if (retval)
+ return retval;
+
+ if (!(rawdev = rawdev_locate(iminor(inode)))) {
+ retval = -ENODEV;
+ goto out;
+ }
+
+ if (!rawdev->serio) {
+ retval = -ENODEV;
+ goto out;
+ }
+
+ if (!(list = kmalloc(sizeof(struct rawdev_list), GFP_KERNEL))) {
+ retval = -ENOMEM;
+ goto out;
+ }
+
+ memset(list, 0, sizeof(struct rawdev_list));
+ list->rawdev = rawdev;
+ file->private_data = list;
+
+ rawdev->refcnt++;
+ list_add_tail(&list->node, &rawdev->list);
+
+out:
+ up(&rawdev_sem);
+ return retval;
+}
+
+/*
+ * rawdev_cleanup() frees rawdev once last reference has been dropped.
+ * It has to be called with rawdev_sem already taken.
+ */
+static int rawdev_cleanup(struct rawdev *rawdev)
+{
+ if (--rawdev->refcnt == 0) {
+ misc_deregister(&rawdev->dev);
+ list_del_init(&rawdev->node);
+ kfree(rawdev);
+
+ return 1;
+ }
+
+ return 0;
+}
+
+static int rawdev_release(struct inode *inode, struct file *file)
+{
+ struct rawdev_list *list = file->private_data;
+ struct rawdev *rawdev = list->rawdev;
+
+ down(&rawdev_sem);
+
+ rawdev_fasync(-1, file, 0);
+ rawdev_cleanup(rawdev);
+
+ up(&rawdev_sem);
+
+ return 0;
+}
+
+static int rawdev_fetch_byte(struct rawdev *rawdev, unsigned char *c)
+{
+ unsigned long flags;
+ int empty;
+
+ spin_lock_irqsave(&rawdev->lock, flags);
+
+ empty = rawdev->head == rawdev->tail;
+ if (!empty) {
+ *c = rawdev->queue[rawdev->tail];
+ rawdev->tail = (rawdev->tail + 1) % RAWDEV_QUEUE_LEN;
+ }
+
+ spin_unlock_irqrestore(&rawdev->lock, flags);
+
+ return !empty;
+}
+
+static ssize_t rawdev_read(struct file *file, char __user *buffer, size_t count, loff_t *ppos)
+{
+ struct rawdev_list *list = file->private_data;
+ struct rawdev *rawdev = list->rawdev;
+ unsigned char c;
+ ssize_t retval;
+
+ /*
+ * Unlike rawdev_write we do not have to take rawdev_sem here since
+ * we do not access rawdev->serio itself, we just check if it is
+ * present. And even if it goes away in the middle of copying data
+ * to userspace it's OK because rawdev will stick around anyway.
+ */
+
+ if (!rawdev->serio)
+ return -ENODEV;
+
+ if (rawdev->head == rawdev->tail && (file->f_flags & O_NONBLOCK))
+ return -EAGAIN;
+
+ retval = wait_event_interruptible(list->rawdev->wait,
+ rawdev->head != rawdev->tail || !rawdev->serio);
+ if (retval)
+ return retval;
+
+ if (!rawdev->serio)
+ return -ENODEV;
+
+ while (retval < count && rawdev_fetch_byte(rawdev, &c)) {
+ if (put_user(c, buffer++))
+ return -EFAULT;
+ retval++;
+ }
+
+ return retval;
+}
+
+static ssize_t rawdev_write(struct file *file, const char __user *buffer, size_t count, loff_t *ppos)
+{
+ struct rawdev_list *list = file->private_data;
+ ssize_t retval;
+ unsigned char c;
+
+ retval = down_interruptible(&rawdev_sem);
+ if (retval)
+ return retval;
+
+ /* Check if underlying serio went away while we were waiting */
+ if (!list->rawdev->serio) {
+ retval = -ENODEV;
+ goto out;
+ }
+
+ /*
+ * Do not hog the device for too long.
+ * The same limit is used in 2.4 psaux implementation which we trying
+ * to follow as close as possible
+ */
+ if (count > 32)
+ count = 32;
+
+ while (count--) {
+ if (get_user(c, buffer++)) {
+ retval = -EFAULT;
+ goto out;
+ }
+ if (serio_write(list->rawdev->serio, c)) {
+ retval = -EIO;
+ goto out;
+ }
+ /* Normally write returns number of bytes written */
+ retval++;
+ }
+
+out:
+ up(&rawdev_sem);
+ return retval;
+}
+
+static unsigned int rawdev_poll(struct file *file, poll_table *wait)
+{
+ struct rawdev_list *list = file->private_data;
+
+ poll_wait(file, &list->rawdev->wait, wait);
+
+ if (list->rawdev->head != list->rawdev->tail)
+ return POLLIN | POLLRDNORM;
+
+ return 0;
+}
+
+struct file_operations rawdev_fops = {
+ .owner = THIS_MODULE,
+ .open = rawdev_open,
+ .release = rawdev_release,
+ .read = rawdev_read,
+ .write = rawdev_write,
+ .poll = rawdev_poll,
+ .fasync = rawdev_fasync,
+};
+
+
+/*********************************************************************
+ * Interface with serio port *
+ *********************************************************************/
+
+/*
+ * rawdev_interrupt gets a byte from the underlying serio port and stores
+ * it in rawdev's ring buffer for rawdev_fetch_byte to fetch.
+ */
+static irqreturn_t rawdev_interrupt(struct serio *serio, unsigned char data,
+ unsigned int dfl, struct pt_regs *regs)
+{
+ struct rawdev *rawdev = serio->private;
+ struct rawdev_list *list;
+ unsigned int head = rawdev->head;
+ unsigned long flags;
+
+ spin_lock_irqsave(&rawdev->lock, flags);
+
+ rawdev->queue[head] = data;
+ head = (head + 1) % RAWDEV_QUEUE_LEN;
+ if (likely(head != rawdev->tail)) {
+ rawdev->head = head;
+ list_for_each_entry(list, &rawdev->list, node)
+ kill_fasync(&list->fasync, SIGIO, POLL_IN);
+ wake_up_interruptible(&rawdev->wait);
+ }
+
+ spin_unlock_irqrestore(&rawdev->lock, flags);
+
+ return IRQ_HANDLED;
+}
+
+static void rawdev_connect(struct serio *serio, struct serio_dev *dev)
+{
+ struct rawdev *rawdev;
+ int err;
+
+ if ((serio->type & SERIO_TYPE) != SERIO_8042_RAW)
+ return;
+
+ if (!(rawdev = kmalloc(sizeof(struct rawdev), GFP_KERNEL))) {
+ printk(KERN_ERR "rawdev.c: can't allocate memory for a device\n");
+ return;
+ }
+
+ down(&rawdev_sem);
+
+ memset(rawdev, 0, sizeof(struct rawdev));
+ snprintf(rawdev->name, sizeof(rawdev->name), "serio_raw%d", rawdev_no++);
+ rawdev->refcnt = 1;
+ rawdev->serio = serio;
+ INIT_LIST_HEAD(&rawdev->list);
+ init_waitqueue_head(&rawdev->wait);
+
+ serio->private = rawdev;
+ if (serio_open(serio, dev))
+ goto out_free;
+
+ list_add_tail(&rawdev->node, &rawdev_list);
+
+ /*
+ * Try binding to char 10,1 (/dev/psaux) first. Assuming that average
+ * system will have at most one port in raw mode it should keep thigs
+ * pretty much the same as 2.4 and earlier kernels.
+ * If 10,1 has already been taken retry with dynamically allocated
+ * minor.
+ */
+ rawdev->dev.minor = PSMOUSE_MINOR;
+ rawdev->dev.name = rawdev->name;
+ rawdev->dev.fops = &rawdev_fops;
+
+ err = misc_register(&rawdev->dev);
+ if (err) {
+ rawdev->dev.minor = MISC_DYNAMIC_MINOR;
+ err = misc_register(&rawdev->dev);
+ }
+
+ if (err) {
+ printk(KERN_INFO "rawdev: failed to register raw access device for %s\n",
+ serio->phys);
+ goto out_close;
+ }
+
+ printk(KERN_INFO "rawdev: raw access enabled on %s (%s, minor %d)\n",
+ serio->phys, rawdev->name, rawdev->dev.minor);
+ goto out;
+
+out_close:
+ serio_close(serio);
+ list_del_init(&rawdev->node);
+out_free:
+ serio->private = NULL;
+ kfree(rawdev);
+out:
+ up(&rawdev_sem);
+}
+
+static int rawdev_reconnect(struct serio *serio)
+{
+ struct rawdev *rawdev = serio->private;
+ struct serio_dev *dev = serio->dev;
+
+ if (!dev || !rawdev) {
+ printk(KERN_DEBUG "rawdev: reconnect request, but serio is disconnected, ignoring...\n");
+ return -1;
+ }
+
+ /*
+ * Nothing needs to be done here, we just need this method to
+ * keep the same device.
+ */
+ return 0;
+}
+
+static void rawdev_disconnect(struct serio *serio)
+{
+ struct rawdev *rawdev;
+
+ down(&rawdev_sem);
+
+ rawdev = serio->private;
+
+ serio_close(serio);
+ serio->private = NULL;
+
+ rawdev->serio = NULL;
+ if (!rawdev_cleanup(rawdev))
+ wake_up_interruptible(&rawdev->wait);
+
+ up(&rawdev_sem);
+}
+
+static struct serio_dev rawdev_dev = {
+ .interrupt = rawdev_interrupt,
+ .connect = rawdev_connect,
+ .reconnect = rawdev_reconnect,
+ .disconnect = rawdev_disconnect,
+};
+
+int __init rawdev_init(void)
+{
+ serio_register_device(&rawdev_dev);
+ return 0;
+}
+
+void __exit rawdev_exit(void)
+{
+ serio_unregister_device(&rawdev_dev);
+}
+
+module_init(rawdev_init);
+module_exit(rawdev_exit);
diff -Nru a/include/linux/serio.h b/include/linux/serio.h
--- a/include/linux/serio.h 2004-06-02 23:08:36 -05:00
+++ b/include/linux/serio.h 2004-06-02 23:08:36 -05:00
@@ -108,6 +108,7 @@
#define SERIO_PC9800 0x04000000UL
#define SERIO_PS_PSTHRU 0x05000000UL
#define SERIO_8042_XL 0x06000000UL
+#define SERIO_8042_RAW 0x07000000UL

#define SERIO_PROTO 0xFFUL
#define SERIO_MSC 0x01