From c636142b025f3026d0ff4dcd6ed4a369b3b93f3d Mon Sep 17 00:00:00 2001
From: Matt DeVillier <matt.devillier@gmail.com>
Date: Mon, 28 Mar 2022 22:35:42 -0500
Subject: drivers/i2c/generic: Add support for i2c device detection

Add 'detect' flag which can be attached to devices which may or may not
be present at runtime, and for which coreboot should probe the i2c bus
to confirm device presence prior to adding an entry for it in the SSDT.

This is useful for boards which may utilize touchpads/touchscreens from
multiple vendors, so that only the device(s) present are added to the
SSDT. This relieves the burden from the OS to detect/probe if a device
is actually present and allows the OS to trust the ACPI _STA value.

Change-Id: I1a4169ed6416d544773a37d29cdcc154d3c28519
Signed-off-by: Matt DeVillier <matt.devillier@gmail.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/63211
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@tutanota.com>
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
---
 src/drivers/i2c/generic/chip.h    | 11 +++++++++++
 src/drivers/i2c/generic/generic.c | 12 ++++++++++++
 2 files changed, 23 insertions(+)

(limited to 'src/drivers')

diff --git a/src/drivers/i2c/generic/chip.h b/src/drivers/i2c/generic/chip.h
index 284c9d1967..a99b09536e 100644
--- a/src/drivers/i2c/generic/chip.h
+++ b/src/drivers/i2c/generic/chip.h
@@ -31,6 +31,17 @@ struct drivers_i2c_generic_config {
 	 */
 	int probed;
 
+	/*
+	 * This flag will add a device property which will indicate
+	 * that coreboot should attempt to detect the device on the i2c
+	 * bus before generating a device entry in the SSDT.
+	 *
+	 * This can be used to declare a device that may not exist on
+	 * the board, for example to support multiple touchpads and/or
+	 * touchscreens.
+	 */
+	int detect;
+
 	/* GPIO used to indicate if this device is present */
 	unsigned int device_present_gpio;
 	unsigned int device_present_gpio_invert;
diff --git a/src/drivers/i2c/generic/generic.c b/src/drivers/i2c/generic/generic.c
index 656b9e6c16..872891b64b 100644
--- a/src/drivers/i2c/generic/generic.c
+++ b/src/drivers/i2c/generic/generic.c
@@ -3,6 +3,7 @@
 #include <acpi/acpi_device.h>
 #include <acpi/acpigen.h>
 #include <console/console.h>
+#include <device/i2c_bus.h>
 #include <device/i2c_simple.h>
 #include <device/device.h>
 #include <device/path.h>
@@ -65,6 +66,17 @@ void i2c_generic_fill_ssdt(const struct device *dev,
 		return;
 	}
 
+	if (config->detect) {
+		struct device *const busdev = i2c_busdev(dev);
+		if (!i2c_dev_detect(busdev, dev->path.i2c.device)) {
+			printk(BIOS_SPEW, "%s: %s at %s -- NOT FOUND, skipping\n",
+				path,
+				config->desc ? : dev->chip_ops->name,
+				dev_path(dev));
+			return;
+		}
+	}
+
 	/* Device */
 	acpigen_write_scope(scope);
 	acpigen_write_device(acpi_device_name(dev));
-- 
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