Message-ID: <20251219031623.10957-1-enelsonmoore@gmail.com>
Date: Thu, 18 Dec 2025 19:16:23 -0800
From: Ethan Nelson-Moore <enelsonmoore@...il.com>
To: linux-kernel@...r.kernel.org
Cc: Rodolfo Giometti <giometti@...eenne.com>,
	Ethan Nelson-Moore <enelsonmoore@...il.com>
Subject: [PATCH] pps: generators: remove broken pps_gen_parport driver

This driver was introduced in January 2011 and has been marked
BROKEN for almost its entire existence (since commit
95b90afec301f050f72740e8696f7cce8a37db5a in March 2011).
It is unlikely anyone will fix the driver at this point.

Signed-off-by: Ethan Nelson-Moore <enelsonmoore@...il.com>
---
 drivers/pps/generators/Kconfig           |   8 -
 drivers/pps/generators/Makefile          |   1 -
 drivers/pps/generators/pps_gen_parport.c | 238 -----------------------
 3 files changed, 247 deletions(-)
 delete mode 100644 drivers/pps/generators/pps_gen_parport.c

diff --git a/drivers/pps/generators/Kconfig b/drivers/pps/generators/Kconfig
index b3f340ed3163..4ef02b3f2576 100644
--- a/drivers/pps/generators/Kconfig
+++ b/drivers/pps/generators/Kconfig
@@ -23,14 +23,6 @@ config PPS_GENERATOR_DUMMY
           This driver can also be built as a module.  If so, the module
           will be called pps_gen-dummy.
 
-config PPS_GENERATOR_PARPORT
-	tristate "Parallel port PPS signal generator"
-	depends on PARPORT && BROKEN
-	help
-	  If you say yes here you get support for a PPS signal generator which
-	  utilizes STROBE pin of a parallel port to send PPS signals. It uses
-	  parport abstraction layer and hrtimers to precisely control the signal.
-
 config PPS_GENERATOR_TIO
 	tristate "TIO PPS signal generator"
 	depends on X86 && CPU_SUP_INTEL
diff --git a/drivers/pps/generators/Makefile b/drivers/pps/generators/Makefile
index e109920e8a2d..5d38774b4a56 100644
--- a/drivers/pps/generators/Makefile
+++ b/drivers/pps/generators/Makefile
@@ -7,7 +7,6 @@ pps_gen_core-y			:= pps_gen.o sysfs.o
 obj-$(CONFIG_PPS_GENERATOR)	:= pps_gen_core.o
 
 obj-$(CONFIG_PPS_GENERATOR_DUMMY)   += pps_gen-dummy.o
-obj-$(CONFIG_PPS_GENERATOR_PARPORT) += pps_gen_parport.o
 obj-$(CONFIG_PPS_GENERATOR_TIO)     += pps_gen_tio.o
 
 ccflags-$(CONFIG_PPS_DEBUG) := -DDEBUG
diff --git a/drivers/pps/generators/pps_gen_parport.c b/drivers/pps/generators/pps_gen_parport.c
deleted file mode 100644
index 05bbf8d30ef1..000000000000
--- a/drivers/pps/generators/pps_gen_parport.c
+++ /dev/null
@@ -1,238 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-or-later
-/*
- * pps_gen_parport.c -- kernel parallel port PPS signal generator
- *
- * Copyright (C) 2009   Alexander Gordeev <lasaine@....cs.msu.su>
- */
-
-
-/*
- * TODO:
- * fix issues when realtime clock is adjusted in a leap
- */
-
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-
-#include <linux/kernel.h>
-#include <linux/module.h>
-#include <linux/init.h>
-#include <linux/time.h>
-#include <linux/hrtimer.h>
-#include <linux/parport.h>
-
-#define SIGNAL		0
-#define NO_SIGNAL	PARPORT_CONTROL_STROBE
-
-/* module parameters */
-
-#define SEND_DELAY_MAX		100000
-
-static unsigned int send_delay = 30000;
-MODULE_PARM_DESC(delay,
-	"Delay between setting and dropping the signal (ns)");
-module_param_named(delay, send_delay, uint, 0);
-
-
-#define SAFETY_INTERVAL	3000	/* set the hrtimer earlier for safety (ns) */
-
-/* internal per port structure */
-struct pps_generator_pp {
-	struct pardevice *pardev;	/* parport device */
-	struct hrtimer timer;
-	long port_write_time;		/* calibrated port write time (ns) */
-};
-
-static struct pps_generator_pp device = {
-	.pardev = NULL,
-};
-
-static int attached;
-
-/* calibrated time between a hrtimer event and the reaction */
-static long hrtimer_error = SAFETY_INTERVAL;
-
-/* the kernel hrtimer event */
-static enum hrtimer_restart hrtimer_event(struct hrtimer *timer)
-{
-	struct timespec64 expire_time, ts1, ts2, ts3, dts;
-	struct pps_generator_pp *dev;
-	struct parport *port;
-	long lim, delta;
-	unsigned long flags;
-
-	/* We have to disable interrupts here. The idea is to prevent
-	 * other interrupts on the same processor to introduce random
-	 * lags while polling the clock. ktime_get_real_ts64() takes <1us on
-	 * most machines while other interrupt handlers can take much
-	 * more potentially.
-	 *
-	 * NB: approx time with blocked interrupts =
-	 * send_delay + 3 * SAFETY_INTERVAL
-	 */
-	local_irq_save(flags);
-
-	/* first of all we get the time stamp... */
-	ktime_get_real_ts64(&ts1);
-	expire_time = ktime_to_timespec64(hrtimer_get_softexpires(timer));
-	dev = container_of(timer, struct pps_generator_pp, timer);
-	lim = NSEC_PER_SEC - send_delay - dev->port_write_time;
-
-	/* check if we are late */
-	if (expire_time.tv_sec != ts1.tv_sec || ts1.tv_nsec > lim) {
-		local_irq_restore(flags);
-		pr_err("we are late this time %ptSp\n", &ts1);
-		goto done;
-	}
-
-	/* busy loop until the time is right for an assert edge */
-	do {
-		ktime_get_real_ts64(&ts2);
-	} while (expire_time.tv_sec == ts2.tv_sec && ts2.tv_nsec < lim);
-
-	/* set the signal */
-	port = dev->pardev->port;
-	port->ops->write_control(port, SIGNAL);
-
-	/* busy loop until the time is right for a clear edge */
-	lim = NSEC_PER_SEC - dev->port_write_time;
-	do {
-		ktime_get_real_ts64(&ts2);
-	} while (expire_time.tv_sec == ts2.tv_sec && ts2.tv_nsec < lim);
-
-	/* unset the signal */
-	port->ops->write_control(port, NO_SIGNAL);
-
-	ktime_get_real_ts64(&ts3);
-
-	local_irq_restore(flags);
-
-	/* update calibrated port write time */
-	dts = timespec64_sub(ts3, ts2);
-	dev->port_write_time =
-		(dev->port_write_time + timespec64_to_ns(&dts)) >> 1;
-
-done:
-	/* update calibrated hrtimer error */
-	dts = timespec64_sub(ts1, expire_time);
-	delta = timespec64_to_ns(&dts);
-	/* If the new error value is bigger then the old, use the new
-	 * value, if not then slowly move towards the new value. This
-	 * way it should be safe in bad conditions and efficient in
-	 * good conditions.
-	 */
-	if (delta >= hrtimer_error)
-		hrtimer_error = delta;
-	else
-		hrtimer_error = (3 * hrtimer_error + delta) >> 2;
-
-	/* update the hrtimer expire time */
-	hrtimer_set_expires(timer,
-			ktime_set(expire_time.tv_sec + 1,
-				NSEC_PER_SEC - (send_delay +
-				dev->port_write_time + SAFETY_INTERVAL +
-				2 * hrtimer_error)));
-
-	return HRTIMER_RESTART;
-}
-
-/* calibrate port write time */
-#define PORT_NTESTS_SHIFT	5
-static void calibrate_port(struct pps_generator_pp *dev)
-{
-	struct parport *port = dev->pardev->port;
-	int i;
-	long acc = 0;
-
-	for (i = 0; i < (1 << PORT_NTESTS_SHIFT); i++) {
-		struct timespec64 a, b;
-		unsigned long irq_flags;
-
-		local_irq_save(irq_flags);
-		ktime_get_real_ts64(&a);
-		port->ops->write_control(port, NO_SIGNAL);
-		ktime_get_real_ts64(&b);
-		local_irq_restore(irq_flags);
-
-		b = timespec64_sub(b, a);
-		acc += timespec64_to_ns(&b);
-	}
-
-	dev->port_write_time = acc >> PORT_NTESTS_SHIFT;
-	pr_info("port write takes %ldns\n", dev->port_write_time);
-}
-
-static inline ktime_t next_intr_time(struct pps_generator_pp *dev)
-{
-	struct timespec64 ts;
-
-	ktime_get_real_ts64(&ts);
-
-	return ktime_set(ts.tv_sec +
-			((ts.tv_nsec > 990 * NSEC_PER_MSEC) ? 1 : 0),
-			NSEC_PER_SEC - (send_delay +
-			dev->port_write_time + 3 * SAFETY_INTERVAL));
-}
-
-static void parport_attach(struct parport *port)
-{
-	struct pardev_cb pps_cb;
-
-	if (send_delay > SEND_DELAY_MAX) {
-		pr_err("delay value should be not greater then %d\n", SEND_DELAY_MAX);
-		return;
-	}
-
-	if (attached) {
-		/* we already have a port */
-		return;
-	}
-
-	memset(&pps_cb, 0, sizeof(pps_cb));
-	pps_cb.private = &device;
-	pps_cb.flags = PARPORT_FLAG_EXCL;
-	device.pardev = parport_register_dev_model(port, KBUILD_MODNAME,
-						   &pps_cb, 0);
-	if (!device.pardev) {
-		pr_err("couldn't register with %s\n", port->name);
-		return;
-	}
-
-	if (parport_claim_or_block(device.pardev) < 0) {
-		pr_err("couldn't claim %s\n", port->name);
-		goto err_unregister_dev;
-	}
-
-	pr_info("attached to %s\n", port->name);
-	attached = 1;
-
-	calibrate_port(&device);
-
-	hrtimer_setup(&device.timer, hrtimer_event, CLOCK_REALTIME, HRTIMER_MODE_ABS);
-	hrtimer_start(&device.timer, next_intr_time(&device), HRTIMER_MODE_ABS);
-
-	return;
-
-err_unregister_dev:
-	parport_unregister_device(device.pardev);
-}
-
-static void parport_detach(struct parport *port)
-{
-	if (port->cad != device.pardev)
-		return;	/* not our port */
-
-	hrtimer_cancel(&device.timer);
-	parport_release(device.pardev);
-	parport_unregister_device(device.pardev);
-}
-
-static struct parport_driver pps_gen_parport_driver = {
-	.name = KBUILD_MODNAME,
-	.match_port = parport_attach,
-	.detach = parport_detach,
-};
-module_parport_driver(pps_gen_parport_driver);
-
-MODULE_AUTHOR("Alexander Gordeev <lasaine@....cs.msu.su>");
-MODULE_DESCRIPTION("parallel port PPS signal generator");
-MODULE_LICENSE("GPL");
-- 
2.43.0

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