Add dev_warn_probe() and improve error handling in

Merge series from Dragan Simic <dsimic@manjaro.org>:

This is a small series that introduces dev_warn_probe() function, which
produces warnings on failed resource acquisitions, and improves error
handling in the probe paths of Rockchip SPI drivers, by using functions
dev_err_probe() and dev_warn_probe() properly in multiple places.

This series also performs a bunch of small, rather trivial code cleanups,
to make the code neater and a bit easier to read.

3 files changed, 115 insertions, 43 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index a4c853411a6b..a84a7b952cfd 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -4980,6 +4980,49 @@ define_dev_printk_level(_dev_info, KERN_INFO);
 
 #endif
 
+static void __dev_probe_failed(const struct device *dev, int err, bool fatal,
+			       const char *fmt, va_list vargsp)
+{
+	struct va_format vaf;
+	va_list vargs;
+
+	/*
+	 * On x86_64 and possibly on other architectures, va_list is actually a
+	 * size-1 array containing a structure.  As a result, function parameter
+	 * vargsp decays from T[1] to T*, and &vargsp has type T** rather than
+	 * T(*)[1], which is expected by its assignment to vaf.va below.
+	 *
+	 * One standard way to solve this mess is by creating a copy in a local
+	 * variable of type va_list and then using a pointer to that local copy
+	 * instead, which is the approach employed here.
+	 */
+	va_copy(vargs, vargsp);
+
+	vaf.fmt = fmt;
+	vaf.va = &vargs;
+
+	switch (err) {
+	case -EPROBE_DEFER:
+		device_set_deferred_probe_reason(dev, &vaf);
+		dev_dbg(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
+		break;
+
+	case -ENOMEM:
+		/* Don't print anything on -ENOMEM, there's already enough output */
+		break;
+
+	default:
+		/* Log fatal final failures as errors, otherwise produce warnings */
+		if (fatal)
+			dev_err(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
+		else
+			dev_warn(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
+		break;
+	}
+
+	va_end(vargs);
+}
+
 /**
  * dev_err_probe - probe error check and log helper
  * @dev: the pointer to the struct device
@@ -4992,7 +5035,7 @@ define_dev_printk_level(_dev_info, KERN_INFO);
  * -EPROBE_DEFER and propagate error upwards.
  * In case of -EPROBE_DEFER it sets also defer probe reason, which can be
  * checked later by reading devices_deferred debugfs attribute.
- * It replaces code sequence::
+ * It replaces the following code sequence::
  *
  * 	if (err != -EPROBE_DEFER)
  * 		dev_err(dev, ...);
@@ -5004,47 +5047,77 @@ define_dev_printk_level(_dev_info, KERN_INFO);
  *
  * 	return dev_err_probe(dev, err, ...);
  *
- * Using this helper in your probe function is totally fine even if @err is
- * known to never be -EPROBE_DEFER.
+ * Using this helper in your probe function is totally fine even if @err
+ * is known to never be -EPROBE_DEFER.
  * The benefit compared to a normal dev_err() is the standardized format
- * of the error code, it being emitted symbolically (i.e. you get "EAGAIN"
- * instead of "-35") and the fact that the error code is returned which allows
- * more compact error paths.
+ * of the error code, which is emitted symbolically (i.e. you get "EAGAIN"
+ * instead of "-35"), and having the error code returned allows more
+ * compact error paths.
  *
  * Returns @err.
  */
 int dev_err_probe(const struct device *dev, int err, const char *fmt, ...)
 {
-	struct va_format vaf;
-	va_list args;
+	va_list vargs;
 
-	va_start(args, fmt);
-	vaf.fmt = fmt;
-	vaf.va = &args;
+	va_start(vargs, fmt);
 
-	switch (err) {
-	case -EPROBE_DEFER:
-		device_set_deferred_probe_reason(dev, &vaf);
-		dev_dbg(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
-		break;
+	/* Use dev_err() for logging when err doesn't equal -EPROBE_DEFER */
+	__dev_probe_failed(dev, err, true, fmt, vargs);
 
-	case -ENOMEM:
-		/*
-		 * We don't print anything on -ENOMEM, there is already enough
-		 * output.
-		 */
-		break;
+	va_end(vargs);
 
-	default:
-		dev_err(dev, "error %pe: %pV", ERR_PTR(err), &vaf);
-		break;
-	}
+	return err;
+}
+EXPORT_SYMBOL_GPL(dev_err_probe);
 
-	va_end(args);
+/**
+ * dev_warn_probe - probe error check and log helper
+ * @dev: the pointer to the struct device
+ * @err: error value to test
+ * @fmt: printf-style format string
+ * @...: arguments as specified in the format string
+ *
+ * This helper implements common pattern present in probe functions for error
+ * checking: print debug or warning message depending if the error value is
+ * -EPROBE_DEFER and propagate error upwards.
+ * In case of -EPROBE_DEFER it sets also defer probe reason, which can be
+ * checked later by reading devices_deferred debugfs attribute.
+ * It replaces the following code sequence::
+ *
+ * 	if (err != -EPROBE_DEFER)
+ * 		dev_warn(dev, ...);
+ * 	else
+ * 		dev_dbg(dev, ...);
+ * 	return err;
+ *
+ * with::
+ *
+ * 	return dev_warn_probe(dev, err, ...);
+ *
+ * Using this helper in your probe function is totally fine even if @err
+ * is known to never be -EPROBE_DEFER.
+ * The benefit compared to a normal dev_warn() is the standardized format
+ * of the error code, which is emitted symbolically (i.e. you get "EAGAIN"
+ * instead of "-35"), and having the error code returned allows more
+ * compact error paths.
+ *
+ * Returns @err.
+ */
+int dev_warn_probe(const struct device *dev, int err, const char *fmt, ...)
+{
+	va_list vargs;
+
+	va_start(vargs, fmt);
+
+	/* Use dev_warn() for logging when err doesn't equal -EPROBE_DEFER */
+	__dev_probe_failed(dev, err, false, fmt, vargs);
+
+	va_end(vargs);
 
 	return err;
 }
-EXPORT_SYMBOL_GPL(dev_err_probe);
+EXPORT_SYMBOL_GPL(dev_warn_probe);
 
 static inline bool fwnode_is_primary(struct fwnode_handle *fwnode)
 {
diff --git a/drivers/spi/spi-rockchip.c b/drivers/spi/spi-rockchip.c
index 794fd94e4833..864e58167417 100644
--- a/drivers/spi/spi-rockchip.c
+++ b/drivers/spi/spi-rockchip.c
@@ -773,15 +773,15 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 
 	rs->apb_pclk = devm_clk_get_enabled(&pdev->dev, "apb_pclk");
 	if (IS_ERR(rs->apb_pclk)) {
-		dev_err(&pdev->dev, "Failed to get apb_pclk\n");
-		ret = PTR_ERR(rs->apb_pclk);
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(rs->apb_pclk),
+				    "Failed to get apb_pclk\n");
 		goto err_put_ctlr;
 	}
 
 	rs->spiclk = devm_clk_get_enabled(&pdev->dev, "spiclk");
 	if (IS_ERR(rs->spiclk)) {
-		dev_err(&pdev->dev, "Failed to get spi_pclk\n");
-		ret = PTR_ERR(rs->spiclk);
+		ret = dev_err_probe(&pdev->dev, PTR_ERR(rs->spiclk),
+				    "Failed to get spi_pclk\n");
 		goto err_put_ctlr;
 	}
 
@@ -817,8 +817,7 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 
 	rs->fifo_len = get_fifo_len(rs);
 	if (!rs->fifo_len) {
-		dev_err(&pdev->dev, "Failed to get fifo length\n");
-		ret = -EINVAL;
+		ret = dev_err_probe(&pdev->dev, -EINVAL, "Failed to get fifo length\n");
 		goto err_put_ctlr;
 	}
 
@@ -858,22 +857,21 @@ static int rockchip_spi_probe(struct platform_device *pdev)
 
 	ctlr->dma_tx = dma_request_chan(rs->dev, "tx");
 	if (IS_ERR(ctlr->dma_tx)) {
-		/* Check tx to see if we need defer probing driver */
-		if (PTR_ERR(ctlr->dma_tx) == -EPROBE_DEFER) {
-			ret = -EPROBE_DEFER;
+		/* Check tx to see if we need to defer driver probing */
+		ret = dev_warn_probe(rs->dev, PTR_ERR(ctlr->dma_tx),
+				     "Failed to request optional TX DMA channel\n");
+		if (ret == -EPROBE_DEFER)
 			goto err_disable_pm_runtime;
-		}
-		dev_warn(rs->dev, "Failed to request TX DMA channel\n");
 		ctlr->dma_tx = NULL;
 	}
 
 	ctlr->dma_rx = dma_request_chan(rs->dev, "rx");
 	if (IS_ERR(ctlr->dma_rx)) {
-		if (PTR_ERR(ctlr->dma_rx) == -EPROBE_DEFER) {
-			ret = -EPROBE_DEFER;
+		/* Check rx to see if we need to defer driver probing */
+		ret = dev_warn_probe(rs->dev, PTR_ERR(ctlr->dma_rx),
+				     "Failed to request optional RX DMA channel\n");
+		if (ret == -EPROBE_DEFER)
 			goto err_free_dma_tx;
-		}
-		dev_warn(rs->dev, "Failed to request RX DMA channel\n");
 		ctlr->dma_rx = NULL;
 	}
 
diff --git a/include/linux/dev_printk.h b/include/linux/dev_printk.h
index ca32b5bb28eb..eb2094e43050 100644
--- a/include/linux/dev_printk.h
+++ b/include/linux/dev_printk.h
@@ -276,6 +276,7 @@ do {									\
 			dev_driver_string(dev), dev_name(dev), ## arg)
 
 __printf(3, 4) int dev_err_probe(const struct device *dev, int err, const char *fmt, ...);
+__printf(3, 4) int dev_warn_probe(const struct device *dev, int err, const char *fmt, ...);
 
 /* Simple helper for dev_err_probe() when ERR_PTR() is to be returned. */
 #define dev_err_ptr_probe(dev, ___err, fmt, ...) \