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From:   Ondrej Zary <linux@zary.sk>
To:     Damien Le Moal <damien.lemoal@opensource.wdc.com>
Subject: Re: [PATCH] pata_parport: add driver (PARIDE replacement)
Date:   Mon, 14 Nov 2022 08:53:10 +0100
User-Agent: KMail/1.9.10
Cc:     Christoph Hellwig <hch@lst.de>,
        Sergey Shtylyov <s.shtylyov@omp.ru>,
        Jens Axboe <axboe@kernel.dk>, Tim Waugh <tim@cyberelk.net>,
        linux-block@vger.kernel.org, linux-parport@lists.infradead.org,
        linux-ide@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20220312144415.20010-1-linux@zary.sk> <202211121217.03948.linux@zary.sk> <51bb45e2-6de5-3608-0ccf-7ee78071fa05@opensource.wdc.com>
In-Reply-To: <51bb45e2-6de5-3608-0ccf-7ee78071fa05@opensource.wdc.com>
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On Monday 14 November 2022, Damien Le Moal wrote:
> On 11/12/22 20:17, Ondrej Zary wrote:
> > On Wednesday 19 October 2022 09:34:31 Christoph Hellwig wrote:
> >> It's been a while - did you get a chance to make some progress on
> >> this?  Do you need any help to unblock you?
> >>
> > 
> > Sorry again, I'm back now. Trying to fix locking problems.
> > Added this to each function for analysis how the functions are called wrt.
> > locking:
> > 
> > 	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
> 
> Do you have your code somewhere that we can look at ?

This is the current version with debug printks. I've also added dump_stack()
to find out the code path but haven't analyzed the output yet.

// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright 2022 Ondrej Zary
 * based on paride.c by Grant R. Guenther <grant@torque.net>
 */
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/parport.h>
#include <linux/pata_parport.h>

#define DRV_NAME "pata_parport"

static DEFINE_IDR(parport_list);
static DEFINE_IDR(protocols);
static DEFINE_IDA(pata_parport_bus_dev_ids);
static DEFINE_MUTEX(pi_mutex);

static bool probe = true;
module_param(probe, bool, 0644);
MODULE_PARM_DESC(probe, "Enable automatic device probing (0=off, 1=on [default])");

static bool verbose;
module_param(verbose, bool, 0644);
MODULE_PARM_DESC(verbose, "Enable verbose messages (0=off [default], 1=on)");

#define DISCONNECT_TIMEOUT	(HZ / 10)

static void pi_connect(struct ata_port *ap)
{
	struct pi_adapter *pi = ap->host->private_data;
	if (spin_is_locked(ap->lock))
		dump_stack();

	del_timer_sync(&pi->timer);
	if (!pi->claimed) {
		pi->claimed = true;
		parport_claim_or_block(pi->pardev);
		pi->proto->connect(pi);
	}
}

static void pi_disconnect(struct pi_adapter *pi)
{
	if (pi->claimed) {
		pi->proto->disconnect(pi);
		parport_release(pi->pardev);
		pi->claimed = false;
	}
}

static void pi_disconnect_timer(struct timer_list *t)
{
	struct pi_adapter *pi = from_timer(pi, t, timer);

	pi_disconnect(pi);
}

/* functions taken from libata-sff.c and converted from direct port I/O */
static void pata_parport_dev_select(struct ata_port *ap, unsigned int device)
{
	struct pi_adapter *pi = ap->host->private_data;
	u8 tmp;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));

	if (device == 0)
		tmp = ATA_DEVICE_OBS;
	else
		tmp = ATA_DEVICE_OBS | ATA_DEV1;

	pi_connect(ap);
	pi->proto->write_regr(pi, 0, ATA_REG_DEVICE, tmp);
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);
	ata_sff_pause(ap);
}

static bool pata_parport_devchk(struct ata_port *ap, unsigned int device)
{
	struct pi_adapter *pi = ap->host->private_data;
	u8 nsect, lbal;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pata_parport_dev_select(ap, device);

	pi_connect(ap);
	pi->proto->write_regr(pi, 0, ATA_REG_NSECT, 0x55);
	pi->proto->write_regr(pi, 0, ATA_REG_LBAL, 0xaa);

	pi->proto->write_regr(pi, 0, ATA_REG_NSECT, 0xaa);
	pi->proto->write_regr(pi, 0, ATA_REG_LBAL, 0x55);

	pi->proto->write_regr(pi, 0, ATA_REG_NSECT, 055);
	pi->proto->write_regr(pi, 0, ATA_REG_LBAL, 0xaa);

	nsect = pi->proto->read_regr(pi, 0, ATA_REG_NSECT);
	lbal = pi->proto->read_regr(pi, 0, ATA_REG_LBAL);
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);

	if ((nsect == 0x55) && (lbal == 0xaa))
		return true;	/* we found a device */

	return false;		/* nothing found */
}

static int pata_parport_bus_softreset(struct ata_port *ap, unsigned int devmask,
				      unsigned long deadline)
{
	struct pi_adapter *pi = ap->host->private_data;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pi_connect(ap);
	/* software reset.  causes dev0 to be selected */
	pi->proto->write_regr(pi, 1, 6, ap->ctl);
	udelay(20);
	pi->proto->write_regr(pi, 1, 6, ap->ctl | ATA_SRST);
	udelay(20);
	pi->proto->write_regr(pi, 1, 6, ap->ctl);
	ap->last_ctl = ap->ctl;
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);

	/* wait the port to become ready */
	return ata_sff_wait_after_reset(&ap->link, devmask, deadline);
}

static int pata_parport_softreset(struct ata_link *link, unsigned int *classes,
				  unsigned long deadline)
{
	struct ata_port *ap = link->ap;
	unsigned int devmask = 0;
	int rc;
	u8 err;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	/* determine if device 0/1 are present */
	if (pata_parport_devchk(ap, 0))
		devmask |= (1 << 0);
	if (pata_parport_devchk(ap, 1))
		devmask |= (1 << 1);

	/* select device 0 again */
	pata_parport_dev_select(ap, 0);

	/* issue bus reset */
	rc = pata_parport_bus_softreset(ap, devmask, deadline);
	if (rc && rc != -ENODEV) {
		ata_link_err(link, "SRST failed (errno=%d)\n", rc);
		return rc;
	}

	/* determine by signature whether we have ATA or ATAPI devices */
	classes[0] = ata_sff_dev_classify(&link->device[0],
					  devmask & (1 << 0), &err);
	if (err != 0x81)
		classes[1] = ata_sff_dev_classify(&link->device[1],
						  devmask & (1 << 1), &err);

	return 0;
}

static u8 pata_parport_check_status(struct ata_port *ap)
{
	u8 status;
	struct pi_adapter *pi = ap->host->private_data;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pi_connect(ap);
	status = pi->proto->read_regr(pi, 0, ATA_REG_STATUS);
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);

	return status;
}

static u8 pata_parport_check_altstatus(struct ata_port *ap)
{
	u8 altstatus;
	struct pi_adapter *pi = ap->host->private_data;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pi_connect(ap);
	altstatus = pi->proto->read_regr(pi, 1, 6);
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);

	return altstatus;
}

static void pata_parport_tf_load(struct ata_port *ap,
				 const struct ata_taskfile *tf)
{
	struct pi_adapter *pi = ap->host->private_data;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pi_connect(ap);
	if (tf->ctl != ap->last_ctl) {
		pi->proto->write_regr(pi, 1, 6, tf->ctl);
		ap->last_ctl = tf->ctl;
		ata_wait_idle(ap);
	}

	if (tf->flags & ATA_TFLAG_ISADDR) {
		if (tf->flags & ATA_TFLAG_LBA48) {
			pi->proto->write_regr(pi, 0, ATA_REG_FEATURE,
					      tf->hob_feature);
			pi->proto->write_regr(pi, 0, ATA_REG_NSECT,
					      tf->hob_nsect);
			pi->proto->write_regr(pi, 0, ATA_REG_LBAL,
					      tf->hob_lbal);
			pi->proto->write_regr(pi, 0, ATA_REG_LBAM,
					      tf->hob_lbam);
			pi->proto->write_regr(pi, 0, ATA_REG_LBAH,
					      tf->hob_lbah);
		}
		pi->proto->write_regr(pi, 0, ATA_REG_FEATURE, tf->feature);
		pi->proto->write_regr(pi, 0, ATA_REG_NSECT, tf->nsect);
		pi->proto->write_regr(pi, 0, ATA_REG_LBAL, tf->lbal);
		pi->proto->write_regr(pi, 0, ATA_REG_LBAM, tf->lbam);
		pi->proto->write_regr(pi, 0, ATA_REG_LBAH, tf->lbah);
	}

	if (tf->flags & ATA_TFLAG_DEVICE)
		pi->proto->write_regr(pi, 0, ATA_REG_DEVICE, tf->device);

	ata_wait_idle(ap);
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);
}

static void pata_parport_tf_read(struct ata_port *ap, struct ata_taskfile *tf)
{
	struct pi_adapter *pi = ap->host->private_data;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pi_connect(ap);
	tf->status = pi->proto->read_regr(pi, 0, ATA_REG_STATUS);
	tf->error = pi->proto->read_regr(pi, 0, ATA_REG_ERR);
	tf->nsect = pi->proto->read_regr(pi, 0, ATA_REG_NSECT);
	tf->lbal = pi->proto->read_regr(pi, 0, ATA_REG_LBAL);
	tf->lbam = pi->proto->read_regr(pi, 0, ATA_REG_LBAM);
	tf->lbah = pi->proto->read_regr(pi, 0, ATA_REG_LBAH);
	tf->device = pi->proto->read_regr(pi, 0, ATA_REG_DEVICE);

	if (tf->flags & ATA_TFLAG_LBA48) {
		pi->proto->write_regr(pi, 1, 6, tf->ctl | ATA_HOB);
		tf->hob_feature = pi->proto->read_regr(pi, 0, ATA_REG_ERR);
		tf->hob_nsect = pi->proto->read_regr(pi, 0, ATA_REG_NSECT);
		tf->hob_lbal = pi->proto->read_regr(pi, 0, ATA_REG_LBAL);
		tf->hob_lbam = pi->proto->read_regr(pi, 0, ATA_REG_LBAM);
		tf->hob_lbah = pi->proto->read_regr(pi, 0, ATA_REG_LBAH);
		pi->proto->write_regr(pi, 1, 6, tf->ctl);
		ap->last_ctl = tf->ctl;
	}
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);
}

static void pata_parport_exec_command(struct ata_port *ap,
				      const struct ata_taskfile *tf)
{
	struct pi_adapter *pi = ap->host->private_data;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pi_connect(ap);
	pi->proto->write_regr(pi, 0, ATA_REG_CMD, tf->command);
	ata_sff_pause(ap);
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);
}

static unsigned int pata_parport_data_xfer(struct ata_queued_cmd *qc,
				unsigned char *buf, unsigned int buflen, int rw)
{
	struct ata_port *ap = qc->dev->link->ap;
	struct pi_adapter *pi = ap->host->private_data;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pi_connect(ap);
	if (rw == READ)
		pi->proto->read_block(pi, buf, buflen);
	else
		pi->proto->write_block(pi, buf, buflen);
	mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);

	return buflen;
}

static void pata_parport_drain_fifo(struct ata_queued_cmd *qc)
{
	int count;
	struct ata_port *ap;
	struct pi_adapter *pi;
	char junk[2];

	/* We only need to flush incoming data when a command was running */
	if (qc == NULL || qc->dma_dir == DMA_TO_DEVICE)
		return;

	ap = qc->ap;
	printk("%s, locked=%d\n", __FUNCTION__, spin_is_locked(ap->lock));
	pi = ap->host->private_data;
	/* Drain up to 64K of data before we give up this recovery method */
	for (count = 0; (pata_parport_check_status(ap) & ATA_DRQ)
						&& count < 65536; count += 2) {
		pi_connect(ap);
		pi->proto->read_block(pi, junk, 2);
		mod_timer(&pi->timer, jiffies + DISCONNECT_TIMEOUT);
	}

	if (count)
		ata_port_dbg(ap, "drained %d bytes to clear DRQ\n", count);
}

static struct ata_port_operations pata_parport_port_ops = {
	.inherits		= &ata_sff_port_ops,

	.softreset		= pata_parport_softreset,
	.hardreset		= NULL,

	.sff_dev_select		= pata_parport_dev_select,
	.sff_check_status	= pata_parport_check_status,
	.sff_check_altstatus	= pata_parport_check_altstatus,
	.sff_tf_load		= pata_parport_tf_load,
	.sff_tf_read		= pata_parport_tf_read,
	.sff_exec_command	= pata_parport_exec_command,
	.sff_data_xfer		= pata_parport_data_xfer,
	.sff_drain_fifo		= pata_parport_drain_fifo,
};

static const struct ata_port_info pata_parport_port_info = {
	.flags		= ATA_FLAG_SLAVE_POSS | ATA_FLAG_PIO_POLLING,
	.pio_mask	= ATA_PIO0,
	/* No DMA */
	.port_ops	= &pata_parport_port_ops,
};

static void pi_release(struct pi_adapter *pi)
{
	parport_unregister_device(pi->pardev);
	if (pi->proto->release_proto)
		pi->proto->release_proto(pi);
	module_put(pi->proto->owner);
}

static int default_test_proto(struct pi_adapter *pi, char *scratch)
{
	int j, k;
	int e[2] = { 0, 0 };

	pi->proto->connect(pi);

	for (j = 0; j < 2; j++) {
		pi->proto->write_regr(pi, 0, 6, 0xa0 + j * 0x10);
		for (k = 0; k < 256; k++) {
			pi->proto->write_regr(pi, 0, 2, k ^ 0xaa);
			pi->proto->write_regr(pi, 0, 3, k ^ 0x55);
			if (pi->proto->read_regr(pi, 0, 2) != (k ^ 0xaa))
				e[j]++;
		}
	}
	pi->proto->disconnect(pi);

	if (verbose)
		dev_info(&pi->dev, "%s: port 0x%x, mode %d, test=(%d,%d)\n",
		       pi->proto->name, pi->port,
		       pi->mode, e[0], e[1]);

	return e[0] && e[1];	/* not here if both > 0 */
}

static int pi_test_proto(struct pi_adapter *pi, char *scratch)
{
	int res;

	parport_claim_or_block(pi->pardev);
	if (pi->proto->test_proto)
		res = pi->proto->test_proto(pi, scratch, verbose);
	else
		res = default_test_proto(pi, scratch);
	parport_release(pi->pardev);

	return res;
}

static bool pi_probe_mode(struct pi_adapter *pi, int max, char *scratch)
{
	int best, range;

	if (pi->mode != -1) {
		if (pi->mode >= max)
			return false;
		range = 3;
		if (pi->mode >= pi->proto->epp_first)
			range = 8;
		if (range == 8 && pi->port % 8)
			return false;
		return !pi_test_proto(pi, scratch);
	}
	best = -1;
	for (pi->mode = 0; pi->mode < max; pi->mode++) {
		range = 3;
		if (pi->mode >= pi->proto->epp_first)
			range = 8;
		if (range == 8 && pi->port % 8)
			break;
		if (!pi_test_proto(pi, scratch))
			best = pi->mode;
	}
	pi->mode = best;
	return best > -1;
}

static bool pi_probe_unit(struct pi_adapter *pi, int unit, char *scratch)
{
	int max, s, e;

	s = unit;
	e = s + 1;

	if (s == -1) {
		s = 0;
		e = pi->proto->max_units;
	}

	if (pi->proto->test_port) {
		parport_claim_or_block(pi->pardev);
		max = pi->proto->test_port(pi);
		parport_release(pi->pardev);
	} else {
		max = pi->proto->max_mode;
	}

	if (pi->proto->probe_unit) {
		parport_claim_or_block(pi->pardev);
		for (pi->unit = s; pi->unit < e; pi->unit++) {
			if (pi->proto->probe_unit(pi)) {
				parport_release(pi->pardev);
				return pi_probe_mode(pi, max, scratch);
			}
		}
		parport_release(pi->pardev);
		return false;
	}

	return pi_probe_mode(pi, max, scratch);
}

static void pata_parport_dev_release(struct device *dev)
{
	struct pi_adapter *pi = container_of(dev, struct pi_adapter, dev);

	kfree(pi);
}

static void pata_parport_bus_release(struct device *dev)
{
	/* nothing to do here but required to avoid warning on device removal */
}

static struct bus_type pata_parport_bus_type = {
	.name = DRV_NAME,
};

static struct device pata_parport_bus = {
	.init_name = DRV_NAME,
	.release = pata_parport_bus_release,
};

/* temporary for old paride protocol modules */
static struct scsi_host_template pata_parport_sht = {
	PATA_PARPORT_SHT("pata_parport")
};

struct pi_device_match {
	struct parport *parport;
	struct pi_protocol *proto;
};

static int pi_find_dev(struct device *dev, void *data)
{
	struct pi_adapter *pi = container_of(dev, struct pi_adapter, dev);
	struct pi_device_match *match = data;

	return pi->pardev->port == match->parport && pi->proto == match->proto;
}

static struct pi_adapter *pi_init_one(struct parport *parport,
			struct pi_protocol *pr, int mode, int unit, int delay)
{
	struct pardev_cb par_cb = { };
	char scratch[512];
	const struct ata_port_info *ppi[] = { &pata_parport_port_info };
	struct ata_host *host;
	struct pi_adapter *pi;
	struct pi_device_match match = { .parport = parport, .proto = pr };

	/*
	 * Abort if there's a device already registered on the same parport
	 * using the same protocol.
	 */
	if (bus_for_each_dev(&pata_parport_bus_type, NULL, &match, pi_find_dev))
		return NULL;

	pi = kzalloc(sizeof(struct pi_adapter), GFP_KERNEL);
	if (!pi)
		return NULL;

	/* set up pi->dev before pi_probe_unit() so it can use dev_printk() */
	pi->dev.parent = &pata_parport_bus;
	pi->dev.bus = &pata_parport_bus_type;
	pi->dev.driver = &pr->driver;
	pi->dev.release = pata_parport_dev_release;
	pi->dev.id = ida_alloc(&pata_parport_bus_dev_ids, GFP_KERNEL);
	if (pi->dev.id < 0)
		return NULL; /* pata_parport_dev_release will do kfree(pi) */
	dev_set_name(&pi->dev, "pata_parport.%u", pi->dev.id);
	if (device_register(&pi->dev)) {
		put_device(&pi->dev);
		goto out_ida_free;
	}

	pi->proto = pr;

	if (!try_module_get(pi->proto->owner))
		goto out_unreg_dev;
	if (pi->proto->init_proto && pi->proto->init_proto(pi) < 0)
		goto out_module_put;

	pi->delay = (delay == -1) ? pi->proto->default_delay : delay;
	pi->mode = mode;
	pi->port = parport->base;

	par_cb.private = pi;
	pi->pardev = parport_register_dev_model(parport, DRV_NAME, &par_cb,
						pi->dev.id);
	if (!pi->pardev)
		goto out_module_put;

	if (!pi_probe_unit(pi, unit, scratch)) {
		dev_info(&pi->dev, "Adapter not found\n");
		goto out_unreg_parport;
	}

	pi->proto->log_adapter(pi, scratch, verbose);

	host = ata_host_alloc_pinfo(&pi->pardev->dev, ppi, 1);
	if (!host)
		goto out_unreg_parport;
	dev_set_drvdata(&pi->dev, host);
	host->private_data = pi;

	ata_port_desc(host->ports[0], "port %s", pi->pardev->port->name);
	ata_port_desc(host->ports[0], "protocol %s", pi->proto->name);

	timer_setup(&pi->timer, pi_disconnect_timer, 0);

	if (ata_host_activate(host, 0, NULL, 0, &pata_parport_sht))
		goto out_unreg_parport;

	return pi;

out_unreg_parport:
	parport_unregister_device(pi->pardev);
	if (pi->proto->release_proto)
		pi->proto->release_proto(pi);
out_module_put:
	module_put(pi->proto->owner);
out_unreg_dev:
	device_unregister(&pi->dev);
out_ida_free:
	ida_free(&pata_parport_bus_dev_ids, pi->dev.id);
	return NULL;
}

int pata_parport_register_driver(struct pi_protocol *pr)
{
	int error;
	struct parport *parport;
	int port_num;

	pr->driver.bus = &pata_parport_bus_type;
	pr->driver.name = pr->name;
	error = driver_register(&pr->driver);
	if (error)
		return error;

	mutex_lock(&pi_mutex);
	error = idr_alloc(&protocols, pr, 0, 0, GFP_KERNEL);
	if (error < 0) {
		driver_unregister(&pr->driver);
		mutex_unlock(&pi_mutex);
		return error;
	}

	pr_info("pata_parport: protocol %s registered\n", pr->name);

	if (probe) {
		/* probe all parports using this protocol */
		idr_for_each_entry(&parport_list, parport, port_num)
			pi_init_one(parport, pr, -1, 0, -1);
	}
	mutex_unlock(&pi_mutex);

	return 0;
}
EXPORT_SYMBOL(pata_parport_register_driver);

void pata_parport_unregister_driver(struct pi_protocol *pr)
{
	struct pi_protocol *pr_iter;
	int id = -1;

	mutex_lock(&pi_mutex);
	idr_for_each_entry(&protocols, pr_iter, id) {
		if (pr_iter == pr)
			break;
	}
	idr_remove(&protocols, id);
	mutex_unlock(&pi_mutex);
	driver_unregister(&pr->driver);
}
EXPORT_SYMBOL(pata_parport_unregister_driver);

static ssize_t new_device_store(struct bus_type *bus, const char *buf,
				size_t count)
{
	char port[12] = "auto";
	char protocol[8] = "auto";
	int mode = -1, unit = -1, delay = -1;
	struct pi_protocol *pr, *pr_wanted;
	struct device_driver *drv;
	struct parport *parport;
	int port_num, port_wanted, pr_num;
	bool ok = false;

	if (sscanf(buf, "%11s %7s %d %d %d",
			port, protocol, &mode, &unit, &delay) < 1)
		return -EINVAL;

	if (sscanf(port, "parport%u", &port_wanted) < 1) {
		if (!strcmp(port, "auto")) {
			port_wanted = -1;
		} else {
			pr_err("invalid port name %s\n", port);
			return -EINVAL;
		}
	}

	drv = driver_find(protocol, &pata_parport_bus_type);
	if (!drv) {
		if (!strcmp(protocol, "auto")) {
			pr_wanted = NULL;
		} else {
			pr_err("protocol %s not found\n", protocol);
			return -EINVAL;
		}
	} else {
		pr_wanted = container_of(drv, struct pi_protocol, driver);
	}

	mutex_lock(&pi_mutex);
	/* walk all parports */
	idr_for_each_entry(&parport_list, parport, port_num) {
		if (port_num == port_wanted || port_wanted == -1) {
			parport = parport_find_number(port_num);
			if (!parport) {
				pr_err("no such port %s\n", port);
				mutex_unlock(&pi_mutex);
				return -ENODEV;
			}
			/* walk all protocols */
			idr_for_each_entry(&protocols, pr, pr_num) {
				if (pr == pr_wanted || !pr_wanted)
					if (pi_init_one(parport, pr, mode, unit,
							delay))
						ok = true;
			}
			parport_put_port(parport);
		}
	}
	mutex_unlock(&pi_mutex);
	if (!ok)
		return -ENODEV;

	return count;
}
static BUS_ATTR_WO(new_device);

static void pi_remove_one(struct device *dev)
{
	struct ata_host *host = dev_get_drvdata(dev);
	struct pi_adapter *pi = host->private_data;

	ata_host_detach(host);
	del_timer_sync(&pi->timer);
	pi_disconnect(pi);
	pi_release(pi);
	device_unregister(dev);
	ida_free(&pata_parport_bus_dev_ids, dev->id);
	/* pata_parport_dev_release will do kfree(pi) */
}

static ssize_t delete_device_store(struct bus_type *bus, const char *buf,
				   size_t count)
{
	struct device *dev;
	char device_name[32];

	if (sscanf(buf, "%31s", device_name) < 1)
		return -EINVAL;

	mutex_lock(&pi_mutex);
	dev = bus_find_device_by_name(bus, NULL, device_name);
	if (!dev) {
		mutex_unlock(&pi_mutex);
		return -ENODEV;
	}

	pi_remove_one(dev);
	mutex_unlock(&pi_mutex);

	return count;
}
static BUS_ATTR_WO(delete_device);

static void pata_parport_attach(struct parport *port)
{
	struct pi_protocol *pr;
	int pr_num, id;

	mutex_lock(&pi_mutex);
	id = idr_alloc(&parport_list, port, port->number, port->number,
		       GFP_KERNEL);
	if (id < 0) {
		mutex_unlock(&pi_mutex);
		return;
	}

	if (probe) {
		/* probe this port using all protocols */
		idr_for_each_entry(&protocols, pr, pr_num)
			pi_init_one(port, pr, -1, 0, -1);
	}
	mutex_unlock(&pi_mutex);
}

static int pi_remove_port(struct device *dev, void *p)
{
	struct ata_host *host = dev_get_drvdata(dev);
	struct pi_adapter *pi = host->private_data;

	if (pi->pardev->port == p)
		pi_remove_one(dev);

	return 0;
}

static void pata_parport_detach(struct parport *port)
{
	mutex_lock(&pi_mutex);
	bus_for_each_dev(&pata_parport_bus_type, NULL, port, pi_remove_port);
	idr_remove(&parport_list, port->number);
	mutex_unlock(&pi_mutex);
}

static struct parport_driver pata_parport_driver = {
	.name = DRV_NAME,
	.match_port = pata_parport_attach,
	.detach = pata_parport_detach,
	.devmodel = true,
};

static __init int pata_parport_init(void)
{
	int error;

	error = bus_register(&pata_parport_bus_type);
	if (error) {
		pr_err("failed to register pata_parport bus, error: %d\n", error);
		return error;
	}

	error = device_register(&pata_parport_bus);
	if (error) {
		pr_err("failed to register pata_parport bus, error: %d\n", error);
		goto out_unregister_bus;
	}

	error = bus_create_file(&pata_parport_bus_type, &bus_attr_new_device);
	if (error) {
		pr_err("unable to create sysfs file, error: %d\n", error);
		goto out_unregister_dev;
	}

	error = bus_create_file(&pata_parport_bus_type, &bus_attr_delete_device);
	if (error) {
		pr_err("unable to create sysfs file, error: %d\n", error);
		goto out_remove_new;
	}

	error = parport_register_driver(&pata_parport_driver);
	if (error) {
		pr_err("unable to register parport driver, error: %d\n", error);
		goto out_remove_del;
	}

	return 0;

out_remove_del:
	bus_remove_file(&pata_parport_bus_type, &bus_attr_delete_device);
out_remove_new:
	bus_remove_file(&pata_parport_bus_type, &bus_attr_new_device);
out_unregister_dev:
	device_unregister(&pata_parport_bus);
out_unregister_bus:
	bus_unregister(&pata_parport_bus_type);
	return error;
}

static __exit void pata_parport_exit(void)
{
	parport_unregister_driver(&pata_parport_driver);
	bus_remove_file(&pata_parport_bus_type, &bus_attr_new_device);
	bus_remove_file(&pata_parport_bus_type, &bus_attr_delete_device);
	device_unregister(&pata_parport_bus);
	bus_unregister(&pata_parport_bus_type);
}

MODULE_AUTHOR("Ondrej Zary");
MODULE_DESCRIPTION("driver for parallel port ATA adapters");
MODULE_LICENSE("GPL");
MODULE_ALIAS("paride");

module_init(pata_parport_init);
module_exit(pata_parport_exit);


-- 
Ondrej Zary