rtc: rework rtc_register_device() resource management

rtc_register_device() is a managed interface but it doesn't use devres
by itself - instead it marks an rtc_device as "registered" and the devres
callback for devm_rtc_allocate_device() takes care of resource release.

This doesn't correspond with the design behind devres where managed
structures should not be aware of being managed. The correct solution
here is to register a separate devres callback for unregistering the
device.

While at it: rename rtc_register_device() to devm_rtc_register_device()
and add it to the list of managed interfaces in devres.rst. This way we
can avoid any potential confusion of driver developers who may expect
there to exist a corresponding unregister function.

Signed-off-by: Bartosz Golaszewski <bgolaszewski@baylibre.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Link: https://lore.kernel.org/r/20201109163409.24301-8-brgl@bgdev.pl

Documentation/driver-api/driver-model/devres.rst

@@ -414,6 +414,7 @@ RESET
 RTC
   devm_rtc_device_register()
   devm_rtc_allocate_device()
+  devm_rtc_register_device()
   devm_rtc_nvmem_register()
 
 SERDEV

arch/alpha/kernel/rtc.c

@@ -216,6 +216,6 @@ alpha_rtc_init(void)
 		rtc->ops = &remote_rtc_ops;
 #endif
 
-	return rtc_register_device(rtc);
+	return devm_rtc_register_device(rtc);
 }
 device_initcall(alpha_rtc_init);

drivers/mfd/menelaus.c

@@ -1119,7 +1119,7 @@ static inline void menelaus_rtc_init(struct menelaus_chip *m)
 		menelaus_write_reg(MENELAUS_RTC_CTRL, m->rtc_control);
 	}
 
-	err = rtc_register_device(m->rtc);
+	err = devm_rtc_register_device(m->rtc);
 	if (err) {
 		if (alarm) {
 			menelaus_remove_irq_work(MENELAUS_RTCALM_IRQ);

drivers/rtc/class.c

@@ -321,8 +321,10 @@ static void rtc_device_get_offset(struct rtc_device *rtc)
  *
  * @rtc: the RTC class device to destroy
  */
-static void rtc_device_unregister(struct rtc_device *rtc)
+static void devm_rtc_unregister_device(void *data)
 {
+	struct rtc_device *rtc = data;
+
 	mutex_lock(&rtc->ops_lock);
 	/*
 	 * Remove innards of this RTC, then disable it, before
@@ -339,10 +341,7 @@ static void devm_rtc_release_device(struct device *dev, void *res)
 {
 	struct rtc_device *rtc = *(struct rtc_device **)res;
 
-	if (rtc->registered)
+	put_device(&rtc->dev);
-		rtc_device_unregister(rtc);
-	else
-		put_device(&rtc->dev);
 }
 
 struct rtc_device *devm_rtc_allocate_device(struct device *dev)
@@ -383,7 +382,7 @@ exit_ida:
 }
 EXPORT_SYMBOL_GPL(devm_rtc_allocate_device);
 
-int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
+int __devm_rtc_register_device(struct module *owner, struct rtc_device *rtc)
 {
 	struct rtc_wkalrm alrm;
 	int err;
@@ -413,7 +412,6 @@ int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
 
 	rtc_proc_add_device(rtc);
 
-	rtc->registered = true;
 	dev_info(rtc->dev.parent, "registered as %s\n",
 		 dev_name(&rtc->dev));
 
@@ -422,9 +420,10 @@ int __rtc_register_device(struct module *owner, struct rtc_device *rtc)
 		rtc_hctosys(rtc);
 #endif
 
-	return 0;
+	return devm_add_action_or_reset(rtc->dev.parent,
+					devm_rtc_unregister_device, rtc);
 }
-EXPORT_SYMBOL_GPL(__rtc_register_device);
+EXPORT_SYMBOL_GPL(__devm_rtc_register_device);
 
 /**
  * devm_rtc_device_register - resource managed rtc_device_register()
@@ -454,7 +453,7 @@ struct rtc_device *devm_rtc_device_register(struct device *dev,
 
 	rtc->ops = ops;
 
-	err = __rtc_register_device(owner, rtc);
+	err = __devm_rtc_register_device(owner, rtc);
 	if (err)
 		return ERR_PTR(err);
 

drivers/rtc/rtc-88pm80x.c

@@ -294,7 +294,7 @@ static int pm80x_rtc_probe(struct platform_device *pdev)
 	info->rtc_dev->ops = &pm80x_rtc_ops;
 	info->rtc_dev->range_max = U32_MAX;
 
-	ret = rtc_register_device(info->rtc_dev);
+	ret = devm_rtc_register_device(info->rtc_dev);
 	if (ret)
 		goto out_rtc;
 

drivers/rtc/rtc-88pm860x.c

@@ -307,7 +307,7 @@ static int pm860x_rtc_probe(struct platform_device *pdev)
 	info->rtc_dev->ops = &pm860x_rtc_ops;
 	info->rtc_dev->range_max = U32_MAX;
 
-	ret = rtc_register_device(info->rtc_dev);
+	ret = devm_rtc_register_device(info->rtc_dev);
 	if (ret)
 		return ret;
 

drivers/rtc/rtc-ab-b5ze-s3.c

@@ -892,7 +892,7 @@ static int abb5zes3_probe(struct i2c_client *client,
 		}
 	}
 
-	ret = rtc_register_device(data->rtc);
+	ret = devm_rtc_register_device(data->rtc);
 
 err:
 	if (ret && data->irq)

drivers/rtc/rtc-ab-eoz9.c

@@ -420,7 +420,7 @@ static int abeoz9_probe(struct i2c_client *client,
 	data->rtc->range_min = RTC_TIMESTAMP_BEGIN_2000;
 	data->rtc->range_max = RTC_TIMESTAMP_END_2099;
 
-	ret = rtc_register_device(data->rtc);
+	ret = devm_rtc_register_device(data->rtc);
 	if (ret)
 		return ret;
 

drivers/rtc/rtc-ab3100.c

@@ -238,7 +238,7 @@ static int __init ab3100_rtc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, rtc);
 
-	return rtc_register_device(rtc);
+	return devm_rtc_register_device(rtc);
 }
 
 static struct platform_driver ab3100_rtc_driver = {

drivers/rtc/rtc-ab8500.c

@@ -404,7 +404,7 @@ static int ab8500_rtc_probe(struct platform_device *pdev)
 	if (err)
 		return err;
 
-	return rtc_register_device(rtc);
+	return devm_rtc_register_device(rtc);
 }
 
 static int ab8500_rtc_remove(struct platform_device *pdev)

drivers/rtc/rtc-abx80x.c

@@ -851,7 +851,7 @@ static int abx80x_probe(struct i2c_client *client,
 		return err;
 	}
 
-	return rtc_register_device(priv->rtc);
+	return devm_rtc_register_device(priv->rtc);
 }
 
 static const struct i2c_device_id abx80x_id[] = {

drivers/rtc/rtc-ac100.c

@@ -610,7 +610,7 @@ static int ac100_rtc_probe(struct platform_device *pdev)
 	if (ret)
 		return ret;
 
-	return rtc_register_device(chip->rtc);
+	return devm_rtc_register_device(chip->rtc);
 }
 
 static int ac100_rtc_remove(struct platform_device *pdev)

drivers/rtc/rtc-armada38x.c

@@ -556,7 +556,7 @@ static __init int armada38x_rtc_probe(struct platform_device *pdev)
 
 	rtc->rtc_dev->range_max = U32_MAX;
 
-	return rtc_register_device(rtc->rtc_dev);
+	return devm_rtc_register_device(rtc->rtc_dev);
 }
 
 #ifdef CONFIG_PM_SLEEP

drivers/rtc/rtc-aspeed.c

@@ -104,7 +104,7 @@ static int aspeed_rtc_probe(struct platform_device *pdev)
 	rtc->rtc_dev->range_min = RTC_TIMESTAMP_BEGIN_1900;
 	rtc->rtc_dev->range_max = 38814989399LL; /* 3199-12-31 23:59:59 */
 
-	return rtc_register_device(rtc->rtc_dev);
+	return devm_rtc_register_device(rtc->rtc_dev);
 }
 
 static const struct of_device_id aspeed_rtc_match[] = {

drivers/rtc/rtc-at91rm9200.c

@@ -538,7 +538,7 @@ static int __init at91_rtc_probe(struct platform_device *pdev)
 
 	rtc->range_min = RTC_TIMESTAMP_BEGIN_1900;
 	rtc->range_max = RTC_TIMESTAMP_END_2099;
-	ret = rtc_register_device(rtc);
+	ret = devm_rtc_register_device(rtc);
 	if (ret)
 		goto err_clk;
 

drivers/rtc/rtc-at91sam9.c

@@ -431,7 +431,7 @@ static int at91_rtc_probe(struct platform_device *pdev)
 		dev_warn(&pdev->dev, "%s: SET TIME!\n",
 			 dev_name(&rtc->rtcdev->dev));
 
-	return rtc_register_device(rtc->rtcdev);
+	return devm_rtc_register_device(rtc->rtcdev);
 
 err_clk:
 	clk_disable_unprepare(rtc->sclk);

drivers/rtc/rtc-au1xxx.c

@@ -104,7 +104,7 @@ static int au1xtoy_rtc_probe(struct platform_device *pdev)
 
 	platform_set_drvdata(pdev, rtcdev);
 
-	return rtc_register_device(rtcdev);
+	return devm_rtc_register_device(rtcdev);
 }
 
 static struct platform_driver au1xrtc_driver = {

drivers/rtc/rtc-bd70528.c

@@ -604,7 +604,7 @@ static int bd70528_probe(struct platform_device *pdev)
 		}
 	}
 
-	return rtc_register_device(rtc);
+	return devm_rtc_register_device(rtc);
 }
 
 static const struct platform_device_id bd718x7_rtc_id[] = {

drivers/rtc/rtc-brcmstb-waketimer.c

@@ -252,7 +252,7 @@ static int brcmstb_waketmr_probe(struct platform_device *pdev)
 	timer->rtc->ops = &brcmstb_waketmr_ops;
 	timer->rtc->range_max = U32_MAX;
 
-	ret = rtc_register_device(timer->rtc);
+	ret = devm_rtc_register_device(timer->rtc);
 	if (ret)
 		goto err_notifier;
 

drivers/rtc/rtc-cadence.c

@@ -336,7 +336,7 @@ static int cdns_rtc_probe(struct platform_device *pdev)
 	writel(0, crtc->regs + CDNS_RTC_HMR);
 	writel(CDNS_RTC_KRTCR_KRTC, crtc->regs + CDNS_RTC_KRTCR);
 
-	ret = rtc_register_device(crtc->rtc_dev);
+	ret = devm_rtc_register_device(crtc->rtc_dev);
 	if (ret)
 		goto err_disable_wakeup;