patch "serdev: Fix detection of UART devices on Apple machines." added to tty-linus

This is a note to let you know that I've just added the patch titled

serdev: Fix detection of UART devices on Apple machines.

to my tty git tree which can be found at
git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-linus branch.

The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.

If you have any questions about this process, please let me know.

From 35d4670aaec7206b5ef19c842ca33076bde562e4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ronald=20Tschal=C3=A4r?= <[email protected]>
Date: Tue, 11 Feb 2020 11:47:23 -0800
Subject: serdev: Fix detection of UART devices on Apple machines.
MIME-Version: 1.0
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On Apple devices the _CRS method returns an empty resource template, and the resource settings are instead provided by the _DSM method. But commit 33364d63c75d6182fa369cea80315cf1bb0ee38e (serdev: Add ACPI devices by ResourceSource field) changed the search for serdev devices to require valid, non-empty resource template, thereby breaking Apple devices and causing bluetooth devices to not be found.

This expands the check so that if we don't find a valid template, and we're on an Apple machine, then just check for the device being an immediate child of the controller and having a "baud" property.

---
 drivers/tty/serdev/core.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

index 42345e79920c..c5f0d936b003 100644
@@ -18,6 +18,7 @@
 #include <linux/sched.h>
 #include <linux/serdev.h>
 #include <linux/slab.h>
+#include <linux/platform_data/x86/apple.h>
 
 static bool is_registered;
 static DEFINE_IDA(ctrl_ida);

@@ -631,6 +632,15 @@ static int acpi_serdev_check_resources(struct serdev_controller *ctrl,
 	if (ret)
 		return ret;
 
+	/*
+	 * Apple machines provide an empty resource template, so on those
+	 * machines just look for immediate children with a "baud" property
+	 * (from the _DSM method) instead.
+	 */
+	if (!lookup.controller_handle && x86_apple_machine &&
+	    !acpi_dev_get_property(adev, "baud", ACPI_TYPE_BUFFER, NULL))
+		acpi_get_parent(adev->handle, &lookup.controller_handle);
+
 	/* Make sure controller and ResourceSource handle match */
 	if (ACPI_HANDLE(ctrl->dev.parent) != lookup.controller_handle)
 		return -ENODEV;

2.25.1