spi: Create helper API to lookup ACPI info for spi device

This can then be used to find a spi resource inside an
ACPI node, and allocate a spi device.

Signed-off-by: Stefan Binding <sbinding@opensource.cirrus.com>

drivers/spi/spi.c

@@ -2410,19 +2410,25 @@ static int acpi_spi_add_resource(struct acpi_resource *ares, void *data)
 	return 1;
 }
 
-static acpi_status acpi_register_spi_device(struct spi_controller *ctlr,
-					    struct acpi_device *adev)
+/**
+ * acpi_spi_device_alloc - Allocate a spi device, and fill it in with ACPI information
+ * @ctlr: controller to which the spi device belongs
+ * @adev: ACPI Device for the spi device
+ *
+ * This should be used to allocate a new spi device from and ACPI Node.
+ * The caller is responsible for calling spi_add_device to register the spi device.
+ *
+ * Return: a pointer to the new device, or ERR_PTR on error.
+ */
+struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
+					 struct acpi_device *adev)
 {
 	acpi_handle parent_handle = NULL;
 	struct list_head resource_list;
 	struct acpi_spi_lookup lookup = {};
 	struct spi_device *spi;
 	int ret;
 
-	if (acpi_bus_get_status(adev) || !adev->status.present ||
-	    acpi_device_enumerated(adev))
-		return AE_OK;
-
 	lookup.ctlr		= ctlr;
 	lookup.irq		= -1;
 
@@ -2433,7 +2439,7 @@ static acpi_status acpi_register_spi_device(struct spi_controller *ctlr,
 
 	if (ret < 0)
 		/* found SPI in _CRS but it points to another controller */
-		return AE_OK;
+		return ERR_PTR(-ENODEV);
 
 	if (!lookup.max_speed_hz &&
 	    ACPI_SUCCESS(acpi_get_parent(adev->handle, &parent_handle)) &&
@@ -2443,23 +2449,43 @@ static acpi_status acpi_register_spi_device(struct spi_controller *ctlr,
 	}
 
 	if (!lookup.max_speed_hz)
-		return AE_OK;
+		return ERR_PTR(-ENODEV);
 
 	spi = spi_alloc_device(ctlr);
 	if (!spi) {
 		dev_err(&ctlr->dev, "failed to allocate SPI device for %s\n",
 			dev_name(&adev->dev));
-		return AE_NO_MEMORY;
+		return ERR_PTR(-ENOMEM);
 	}
 
-
 	ACPI_COMPANION_SET(&spi->dev, adev);
 	spi->max_speed_hz	= lookup.max_speed_hz;
 	spi->mode		|= lookup.mode;
 	spi->irq		= lookup.irq;
 	spi->bits_per_word	= lookup.bits_per_word;
 	spi->chip_select	= lookup.chip_select;
 
+	return spi;
+}
+EXPORT_SYMBOL_GPL(acpi_spi_device_alloc);
+
+static acpi_status acpi_register_spi_device(struct spi_controller *ctlr,
+					    struct acpi_device *adev)
+{
+	struct spi_device *spi;
+
+	if (acpi_bus_get_status(adev) || !adev->status.present ||
+	    acpi_device_enumerated(adev))
+		return AE_OK;
+
+	spi = acpi_spi_device_alloc(ctlr, adev);
+	if (IS_ERR(spi)) {
+		if (PTR_ERR(spi) == -ENOMEM)
+			return AE_NO_MEMORY;
+		else
+			return AE_OK;
+	}
+
 	acpi_set_modalias(adev, acpi_device_hid(adev), spi->modalias,
 			  sizeof(spi->modalias));
 

include/linux/spi/spi.h

@@ -16,6 +16,7 @@
 #include <linux/gpio/consumer.h>
 
 #include <uapi/linux/spi/spi.h>
+#include <linux/acpi.h>
 
 struct dma_chan;
 struct software_node;
@@ -759,6 +760,17 @@ extern int devm_spi_register_controller(struct device *dev,
 					struct spi_controller *ctlr);
 extern void spi_unregister_controller(struct spi_controller *ctlr);
 
+#if IS_ENABLED(CONFIG_ACPI)
+extern struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
+						struct acpi_device *adev);
+#else
+static inline struct spi_device *acpi_spi_device_alloc(struct spi_controller *ctlr,
+						       struct acpi_device *adev);
+{
+	return ERR_PTR(-EOPNOTSUPP);
+}
+#endif
+
 /*
  * SPI resource management while processing a SPI message
  */