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Tue, 18 Nov 2025 13:04:10 -0800 (PST) Sender: Guenter Roeck From: Guenter Roeck To: Wim Van Sebroeck Cc: linux-watchdog@vger.kernel.org, linux-kernel@vger.kernel.org, Guenter Roeck Subject: [PATCH] watchdog: Always return time left until watchdog times out Date: Tue, 18 Nov 2025 13:04:07 -0800 Message-ID: <20251118210407.2362338-1-linux@roeck-us.net> X-Mailer: git-send-email 2.45.2 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The watchdog core knows when the most recent keepalive was sent. It also knows the configured timeout. With that, it can always calculate and return the time left until a watchdog times out, even if its driver does not support it. Convert watchdog_get_timeleft() into a void function. It never returns an error after this patch is applied, so the error checks in the calling code are now pointless and can be removed. Signed-off-by: Guenter Roeck --- Tested on system which supports reading the remaining time from the hardware. Confirmed that the calculated remaining time is never more than 1 second different than the time reported by the hardware. drivers/watchdog/watchdog_dev.c | 35 ++++++++++++++------------------- 1 file changed, 15 insertions(+), 20 deletions(-) diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_de= v.c index 8369fd94fc1a..9a5e544b886b 100644 --- a/drivers/watchdog/watchdog_dev.c +++ b/drivers/watchdog/watchdog_dev.c @@ -424,20 +424,22 @@ static int watchdog_set_pretimeout(struct watchdog_de= vice *wdd, * * Get the time before a watchdog will reboot (if not pinged). * The caller must hold wd_data->lock. - * - * Return: 0 if successful, error otherwise. */ -static int watchdog_get_timeleft(struct watchdog_device *wdd, - unsigned int *timeleft) +static void watchdog_get_timeleft(struct watchdog_device *wdd, + unsigned int *timeleft) { *timeleft =3D 0; =20 - if (!wdd->ops->get_timeleft) - return -EOPNOTSUPP; + if (wdd->ops->get_timeleft) { + *timeleft =3D wdd->ops->get_timeleft(wdd); + } else { + struct watchdog_core_data *wd_data =3D wdd->wd_data; + s64 last_keepalive_ms =3D ktime_ms_delta(ktime_get(), wd_data->last_keep= alive); + s64 last_keepalive =3D DIV_ROUND_UP_ULL(last_keepalive_ms, 1000); =20 - *timeleft =3D wdd->ops->get_timeleft(wdd); - - return 0; + if (wdd->timeout > last_keepalive) + *timeleft =3D wdd->timeout - last_keepalive; + } } =20 #ifdef CONFIG_WATCHDOG_SYSFS @@ -499,16 +501,13 @@ static ssize_t timeleft_show(struct device *dev, stru= ct device_attribute *attr, { struct watchdog_device *wdd =3D dev_get_drvdata(dev); struct watchdog_core_data *wd_data =3D wdd->wd_data; - ssize_t status; unsigned int val; =20 mutex_lock(&wd_data->lock); - status =3D watchdog_get_timeleft(wdd, &val); + watchdog_get_timeleft(wdd, &val); mutex_unlock(&wd_data->lock); - if (!status) - status =3D sysfs_emit(buf, "%u\n", val); =20 - return status; + return sysfs_emit(buf, "%u\n", val); } static DEVICE_ATTR_RO(timeleft); =20 @@ -624,9 +623,7 @@ static umode_t wdt_is_visible(struct kobject *kobj, str= uct attribute *attr, struct watchdog_device *wdd =3D dev_get_drvdata(dev); umode_t mode =3D attr->mode; =20 - if (attr =3D=3D &dev_attr_timeleft.attr && !wdd->ops->get_timeleft) - mode =3D 0; - else if (attr =3D=3D &dev_attr_pretimeout.attr && !watchdog_have_pretimeo= ut(wdd)) + if (attr =3D=3D &dev_attr_pretimeout.attr && !watchdog_have_pretimeout(wd= d)) mode =3D 0; else if ((attr =3D=3D &dev_attr_pretimeout_governor.attr || attr =3D=3D &dev_attr_pretimeout_available_governors.attr) && @@ -825,9 +822,7 @@ static long watchdog_ioctl(struct file *file, unsigned = int cmd, err =3D put_user(wdd->timeout, p); break; case WDIOC_GETTIMELEFT: - err =3D watchdog_get_timeleft(wdd, &val); - if (err < 0) - break; + watchdog_get_timeleft(wdd, &val); err =3D put_user(val, p); break; case WDIOC_SETPRETIMEOUT: --=20 2.45.2