iio: dac: adi-axi-dac: improve probe() error messaging

The current error handling for calls such as devm_clk_get_enabled() in
the adi-axi-dac probe() function means that, if a property such as
'clocks' (for example) is not present in the devicetree when booting a
kernel with the driver enabled, the resulting error message will be
vague, e.g.:

|adi_axi_dac 44a00000.dac: probe with driver adi_axi_dac failed with error -2

Change the devm_clk_get_enabled(), devm_regmap_init_mmio(), and
devm_iio_backend_register() checks to use dev_err_probe() with some
context for easier debugging.

After the change:

|adi_axi_dac 44a00000.dac: error -ENOENT: failed to get clock
|adi_axi_dac 44a00000.dac: probe with driver adi_axi_dac failed with error -2
Suggested-by: Nuno Sa <nuno.sa@analog.com>
Tested-by: Angelo Dureghello <adureghello@baylibre.com>
Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
Link: https://patch.msgid.link/20240617151820.3337034-1-tgamblin@baylibre.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/dac/adi-axi-dac.c

@@ -545,7 +545,8 @@ static int axi_dac_probe(struct platform_device *pdev)
 
 	clk = devm_clk_get_enabled(&pdev->dev, NULL);
 	if (IS_ERR(clk))
-		return PTR_ERR(clk);
+		return dev_err_probe(&pdev->dev, PTR_ERR(clk),
+				     "failed to get clock\n");
 
 	base = devm_platform_ioremap_resource(pdev, 0);
 	if (IS_ERR(base))
@@ -555,7 +556,8 @@ static int axi_dac_probe(struct platform_device *pdev)
 	st->regmap = devm_regmap_init_mmio(&pdev->dev, base,
 					   &axi_dac_regmap_config);
 	if (IS_ERR(st->regmap))
-		return PTR_ERR(st->regmap);
+		return dev_err_probe(&pdev->dev, PTR_ERR(st->regmap),
+				     "failed to init register map\n");
 
 	/*
 	 * Force disable the core. Up to the frontend to enable us. And we can
@@ -601,7 +603,8 @@ static int axi_dac_probe(struct platform_device *pdev)
 	mutex_init(&st->lock);
 	ret = devm_iio_backend_register(&pdev->dev, &axi_dac_generic, st);
 	if (ret)
-		return ret;
+		return dev_err_probe(&pdev->dev, ret,
+				     "failed to register iio backend\n");
 
 	dev_info(&pdev->dev, "AXI DAC IP core (%d.%.2d.%c) probed\n",
 		 ADI_AXI_PCORE_VER_MAJOR(ver),