// SPDX-License-Identifier: GPL-2.0-only
/* display7seg.c - Driver implementation for the 7-segment display
 *                 present on Sun Microsystems CP1400 and CP1500
 *
 * Copyright (c) 2000 Eric Brower (ebrower@usa.net)
 */

#include <linux/device.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/fs.h>
#include <linux/errno.h>
#include <linux/major.h>
#include <linux/miscdevice.h>
#include <linux/ioport.h>               /* request_region */
#include <linux/slab.h>
#include <linux/mutex.h>
#include <linux/of.h>
#include <linux/of_device.h>
#include <linux/atomic.h>
#include <linux/uaccess.h>              /* put_/get_user                        */
#include <asm/io.h>

#include <asm/display7seg.h>

#define DRIVER_NAME     "d7s"
#define PFX             DRIVER_NAME ": "

static DEFINE_MUTEX(d7s_mutex);
static int sol_compat = 0;              /* Solaris compatibility mode   */

/* Solaris compatibility flag -
 * The Solaris implementation omits support for several
 * documented driver features (ref Sun doc 806-0180-03).  
 * By default, this module supports the documented driver 
 * abilities, rather than the Solaris implementation:
 *
 *      1) Device ALWAYS reverts to OBP-specified FLIPPED mode
 *         upon closure of device or module unload.
 *      2) Device ioctls D7SIOCRD/D7SIOCWR honor toggling of
 *         FLIP bit
 *
 * If you wish the device to operate as under Solaris,
 * omitting above features, set this parameter to non-zero.
 */
module_param(sol_compat, int, 0);
MODULE_PARM_DESC(sol_compat, 
                 "Disables documented functionality omitted from Solaris driver");

MODULE_AUTHOR("Eric Brower <ebrower@usa.net>");
MODULE_DESCRIPTION("7-Segment Display driver for Sun Microsystems CP1400/1500");
MODULE_LICENSE("GPL");

struct d7s {
        void __iomem    *regs;
        bool            flipped;
};
struct d7s *d7s_device;

/*
 * Register block address- see header for details
 * -----------------------------------------
 * | DP | ALARM | FLIP | 4 | 3 | 2 | 1 | 0 |
 * -----------------------------------------
 *
 * DP           - Toggles decimal point on/off 
 * ALARM        - Toggles "Alarm" LED green/red
 * FLIP         - Inverts display for upside-down mounted board
 * bits 0-4     - 7-segment display contents
 */
static atomic_t d7s_users = ATOMIC_INIT(0);

static int d7s_open(struct inode *inode, struct file *f)
{
        if (D7S_MINOR != iminor(inode))
                return -ENODEV;
        atomic_inc(&d7s_users);
        return 0;
}

static int d7s_release(struct inode *inode, struct file *f)
{
        /* Reset flipped state to OBP default only if
         * no other users have the device open and we
         * are not operating in solaris-compat mode
         */
        if (atomic_dec_and_test(&d7s_users) && !sol_compat) {
                struct d7s *p = d7s_device;
                u8 regval = 0;

                regval = readb(p->regs);
                if (p->flipped)
                        regval |= D7S_FLIP;
                else
                        regval &= ~D7S_FLIP;
                writeb(regval, p->regs);
        }

        return 0;
}

static long d7s_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
{
        struct d7s *p = d7s_device;
        u8 regs = readb(p->regs);
        int error = 0;
        u8 ireg = 0;

        if (D7S_MINOR != iminor(file_inode(file)))
                return -ENODEV;

        mutex_lock(&d7s_mutex);
        switch (cmd) {
        case D7SIOCWR:
                /* assign device register values we mask-out D7S_FLIP
                 * if in sol_compat mode
                 */
                if (get_user(ireg, (int __user *) arg)) {
                        error = -EFAULT;
                        break;
                }
                if (sol_compat) {
                        if (regs & D7S_FLIP)
                                ireg |= D7S_FLIP;
                        else
                                ireg &= ~D7S_FLIP;
                }
                writeb(ireg, p->regs);
                break;

        case D7SIOCRD:
                /* retrieve device register values
                 * NOTE: Solaris implementation returns D7S_FLIP bit
                 * as toggled by user, even though it does not honor it.
                 * This driver will not misinform you about the state
                 * of your hardware while in sol_compat mode
                 */
                if (put_user(regs, (int __user *) arg)) {
                        error = -EFAULT;
                        break;
                }
                break;

        case D7SIOCTM:
                /* toggle device mode-- flip display orientation */
                regs ^= D7S_FLIP;
                writeb(regs, p->regs);
                break;
        }
        mutex_unlock(&d7s_mutex);

        return error;
}

static const struct file_operations d7s_fops = {
        .owner =                THIS_MODULE,
        .unlocked_ioctl =       d7s_ioctl,
        .compat_ioctl =         compat_ptr_ioctl,
        .open =                 d7s_open,
        .release =              d7s_release,
        .llseek = noop_llseek,
};

static struct miscdevice d7s_miscdev = {
        .minor          = D7S_MINOR,
        .name           = DRIVER_NAME,
        .fops           = &d7s_fops
};

static int d7s_probe(struct platform_device *op)
{
        struct device_node *opts;
        int err = -EINVAL;
        struct d7s *p;
        u8 regs;

        if (d7s_device)
                goto out;

        p = devm_kzalloc(&op->dev, sizeof(*p), GFP_KERNEL);
        err = -ENOMEM;
        if (!p)
                goto out;

        p->regs = of_ioremap(&op->resource[0], 0, sizeof(u8), "d7s");
        if (!p->regs) {
                printk(KERN_ERR PFX "Cannot map chip registers\n");
                goto out;
        }

        err = misc_register(&d7s_miscdev);
        if (err) {
                printk(KERN_ERR PFX "Unable to acquire miscdevice minor %i\n",
                       D7S_MINOR);
                goto out_iounmap;
        }

        /* OBP option "d7s-flipped?" is honored as default for the
         * device, and reset default when detached
         */
        regs = readb(p->regs);
        opts = of_find_node_by_path("/options");
        if (opts &&
            of_get_property(opts, "d7s-flipped?", NULL))
                p->flipped = true;

        if (p->flipped)
                regs |= D7S_FLIP;
        else
                regs &= ~D7S_FLIP;

        writeb(regs,  p->regs);

        printk(KERN_INFO PFX "7-Segment Display%pOF at [%s:0x%llx] %s\n",
               op->dev.of_node,
               (regs & D7S_FLIP) ? " (FLIPPED)" : "",
               op->resource[0].start,
               sol_compat ? "in sol_compat mode" : "");

        dev_set_drvdata(&op->dev, p);
        d7s_device = p;
        err = 0;
        of_node_put(opts);

out:
        return err;

out_iounmap:
        of_iounmap(&op->resource[0], p->regs, sizeof(u8));
        goto out;
}

static int d7s_remove(struct platform_device *op)
{
        struct d7s *p = dev_get_drvdata(&op->dev);
        u8 regs = readb(p->regs);

        /* Honor OBP d7s-flipped? unless operating in solaris-compat mode */
        if (sol_compat) {
                if (p->flipped)
                        regs |= D7S_FLIP;
                else
                        regs &= ~D7S_FLIP;
                writeb(regs, p->regs);
        }

        misc_deregister(&d7s_miscdev);
        of_iounmap(&op->resource[0], p->regs, sizeof(u8));

        return 0;
}

static const struct of_device_id d7s_match[] = {
        {
                .name = "display7seg",
        },
        {},
};
MODULE_DEVICE_TABLE(of, d7s_match);

static struct platform_driver d7s_driver = {
        .driver = {
                .name = DRIVER_NAME,
                .of_match_table = d7s_match,
        },
        .probe          = d7s_probe,
        .remove         = d7s_remove,
};

module_platform_driver(d7s_driver);