mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/chenhuacai/linux-loongson
synced 2025-08-27 06:50:37 +00:00
12c409aa1e
Because pps_cdev_poll() returns unconditionally EPOLLIN,
a user space program that calls select/poll get always an immediate data
ready-to-read response. As a result the intended use to wait until next
data becomes ready does not work.
User space snippet:
struct pollfd pollfd = {
.fd = open("/dev/pps0", O_RDONLY),
.events = POLLIN|POLLERR,
.revents = 0 };
while(1) {
poll(&pollfd, 1, 2000/*ms*/); // returns immediate, but should wait
if(revents & EPOLLIN) { // always true
struct pps_fdata fdata;
memset(&fdata, 0, sizeof(memdata));
ioctl(PPS_FETCH, &fdata); // currently fetches data at max speed
}
}
Lets remember the last fetch event counter and compare this value
in pps_cdev_poll() with most recent event counter
and return 0 if they are equal.
Signed-off-by: Denis OSTERLAND-HEIM <denis.osterland@diehl.com>
Co-developed-by: Rodolfo Giometti <giometti@enneenne.com>
Signed-off-by: Rodolfo Giometti <giometti@enneenne.com>
Fixes: eae9d2ba0c ("LinuxPPS: core support")
Link: https://lore.kernel.org/all/f6bed779-6d59-4f0f-8a59-b6312bd83b4e@enneenne.com/
Acked-by: Rodolfo Giometti <giometti@enneenne.com>
Link: https://lore.kernel.org/r/c3c50ad1eb19ef553eca8a57c17f4c006413ab70.camel@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
121 lines
2.9 KiB
C
121 lines
2.9 KiB
C
/* SPDX-License-Identifier: GPL-2.0-or-later */
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/*
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* PPS API kernel header
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*
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* Copyright (C) 2009 Rodolfo Giometti <giometti@linux.it>
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*/
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#ifndef LINUX_PPS_KERNEL_H
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#define LINUX_PPS_KERNEL_H
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#include <linux/pps.h>
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#include <linux/cdev.h>
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#include <linux/device.h>
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#include <linux/time.h>
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/*
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* Global defines
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*/
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struct pps_device;
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/* The specific PPS source info */
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struct pps_source_info {
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char name[PPS_MAX_NAME_LEN]; /* symbolic name */
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char path[PPS_MAX_NAME_LEN]; /* path of connected device */
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int mode; /* PPS allowed mode */
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void (*echo)(struct pps_device *pps,
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int event, void *data); /* PPS echo function */
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struct module *owner;
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struct device *dev; /* Parent device for device_create */
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};
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struct pps_event_time {
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#ifdef CONFIG_NTP_PPS
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struct timespec64 ts_raw;
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#endif /* CONFIG_NTP_PPS */
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struct timespec64 ts_real;
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};
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/* The main struct */
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struct pps_device {
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struct pps_source_info info; /* PSS source info */
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struct pps_kparams params; /* PPS current params */
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__u32 assert_sequence; /* PPS assert event seq # */
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__u32 clear_sequence; /* PPS clear event seq # */
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struct pps_ktime assert_tu;
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struct pps_ktime clear_tu;
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int current_mode; /* PPS mode at event time */
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unsigned int last_ev; /* last PPS event id */
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unsigned int last_fetched_ev; /* last fetched PPS event id */
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wait_queue_head_t queue; /* PPS event queue */
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unsigned int id; /* PPS source unique ID */
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void const *lookup_cookie; /* For pps_lookup_dev() only */
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struct device dev;
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struct fasync_struct *async_queue; /* fasync method */
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spinlock_t lock;
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};
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/*
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* Global variables
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*/
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extern const struct attribute_group *pps_groups[];
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/*
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* Internal functions.
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*
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* These are not actually part of the exported API, but this is a
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* convenient header file to put them in.
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*/
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extern int pps_register_cdev(struct pps_device *pps);
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extern void pps_unregister_cdev(struct pps_device *pps);
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/*
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* Exported functions
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*/
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extern struct pps_device *pps_register_source(
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struct pps_source_info *info, int default_params);
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extern void pps_unregister_source(struct pps_device *pps);
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extern void pps_event(struct pps_device *pps,
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struct pps_event_time *ts, int event, void *data);
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/* Look up a pps_device by magic cookie */
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struct pps_device *pps_lookup_dev(void const *cookie);
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static inline void timespec_to_pps_ktime(struct pps_ktime *kt,
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struct timespec64 ts)
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{
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kt->sec = ts.tv_sec;
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kt->nsec = ts.tv_nsec;
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}
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static inline void pps_get_ts(struct pps_event_time *ts)
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{
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struct system_time_snapshot snap;
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ktime_get_snapshot(&snap);
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ts->ts_real = ktime_to_timespec64(snap.real);
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#ifdef CONFIG_NTP_PPS
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ts->ts_raw = ktime_to_timespec64(snap.raw);
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#endif
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}
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/* Subtract known time delay from PPS event time(s) */
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static inline void pps_sub_ts(struct pps_event_time *ts, struct timespec64 delta)
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{
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ts->ts_real = timespec64_sub(ts->ts_real, delta);
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#ifdef CONFIG_NTP_PPS
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ts->ts_raw = timespec64_sub(ts->ts_raw, delta);
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#endif
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}
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#endif /* LINUX_PPS_KERNEL_H */
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