platform/surface: dtx: Add support for native SSAM devices

Add support for native SSAM devices to the DTX driver. This allows
support for the Surface Book 3, on which the DTX device is not present
in ACPI.

Signed-off-by: Maximilian Luz <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Hans de Goede <[e-mail]>

drivers/platform/surface/Kconfig

···
 	  behavior of this process, which includes the option to abort it in
 	  case the base is still in use or speed it up in case it is not.
 
+	  Note that this module can be built without support for the Surface
+	  Aggregator Bus (i.e. CONFIG_SURFACE_AGGREGATOR_BUS=n). In that case,
+	  some devices, specifically the Surface Book 3, will not be supported.
+
 config SURFACE_GPE
 	tristate "Surface GPE/Lid Support Driver"
 	depends on DMI

drivers/platform/surface/surface_dtx.c

···
 #include <linux/workqueue.h>
 
 #include <linux/surface_aggregator/controller.h>
+#include <linux/surface_aggregator/device.h>
 #include <linux/surface_aggregator/dtx.h>
 
 
···
 		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
 	},
 };
-module_platform_driver(surface_dtx_platform_driver);
+
+
+/* -- SSAM device driver. --------------------------------------------------- */
+
+#ifdef CONFIG_SURFACE_AGGREGATOR_BUS
+
+static int surface_dtx_ssam_probe(struct ssam_device *sdev)
+{
+	struct sdtx_device *ddev;
+
+	ddev = sdtx_device_create(&sdev->dev, sdev->ctrl);
+	if (IS_ERR(ddev))
+		return PTR_ERR(ddev);
+
+	ssam_device_set_drvdata(sdev, ddev);
+	return 0;
+}
+
+static void surface_dtx_ssam_remove(struct ssam_device *sdev)
+{
+	sdtx_device_destroy(ssam_device_get_drvdata(sdev));
+}
+
+static const struct ssam_device_id surface_dtx_ssam_match[] = {
+	{ SSAM_SDEV(BAS, 0x01, 0x00, 0x00) },
+	{ },
+};
+MODULE_DEVICE_TABLE(ssam, surface_dtx_ssam_match);
+
+static struct ssam_device_driver surface_dtx_ssam_driver = {
+	.probe = surface_dtx_ssam_probe,
+	.remove = surface_dtx_ssam_remove,
+	.match_table = surface_dtx_ssam_match,
+	.driver = {
+		.name = "surface_dtx",
+		.pm = &surface_dtx_pm_ops,
+		.probe_type = PROBE_PREFER_ASYNCHRONOUS,
+	},
+};
+
+static int ssam_dtx_driver_register(void)
+{
+	return ssam_device_driver_register(&surface_dtx_ssam_driver);
+}
+
+static void ssam_dtx_driver_unregister(void)
+{
+	ssam_device_driver_unregister(&surface_dtx_ssam_driver);
+}
+
+#else /* CONFIG_SURFACE_AGGREGATOR_BUS */
+
+static int ssam_dtx_driver_register(void)
+{
+	return 0;
+}
+
+static void ssam_dtx_driver_unregister(void)
+{
+}
+
+#endif /* CONFIG_SURFACE_AGGREGATOR_BUS */
+
+
+/* -- Module setup. --------------------------------------------------------- */
+
+static int __init surface_dtx_init(void)
+{
+	int status;
+
+	status = ssam_dtx_driver_register();
+	if (status)
+		return status;
+
+	status = platform_driver_register(&surface_dtx_platform_driver);
+	if (status)
+		ssam_dtx_driver_unregister();
+
+	return status;
+}
+module_init(surface_dtx_init);
+
+static void __exit surface_dtx_exit(void)
+{
+	platform_driver_unregister(&surface_dtx_platform_driver);
+	ssam_dtx_driver_unregister();
+}
+module_exit(surface_dtx_exit);
 
 MODULE_AUTHOR("Maximilian Luz <[e-mail]>");
 MODULE_DESCRIPTION("Detachment-system driver for Surface System Aggregator Module");