Applied "spi: spidev: Add ACPI probing support" to the spi tree

[Mark Brown <broonie@xxxxxxxxxx>]

The patch

   spi: spidev: Add ACPI probing support

has been applied to the spi tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/spi.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From cf9f4327a306be58df6c0b3817d7ef06a2a3da03 Mon Sep 17 00:00:00 2001
From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Date: Mon, 4 Jul 2016 17:18:15 +0300
Subject: [PATCH] spi: spidev: Add ACPI probing support

Some IoT and maker software stacks are using spidev to perform raw access
to the SPI bus instead of relying existing drivers provided by the kernel.
They then implement their own "drivers" in userspace on top of the spidev
raw interface. This is far from being an ideal solution but we do not want
to prevent using mainline Linux in these devices.

Now, it turns out that Windows has similar SPI devices than spidev which
allow raw access on the SPI bus to userspace programs as described in the
link below:

  https://msdn.microsoft.com/windows/hardware/drivers/spb/spi-tests-in-mitt

These SPI test devices are also meant to be used during development and
testing.

In order to allow usage of spidev for development and testing in Linux, add
those same ACPI IDs to the spidev driver (which is Linux counterpart of the
Windows SPI test devices), but complain loudly so that users know it is not
good idea to use it in production systems. Instead they should be using
proper drivers for peripherals connected to the SPI bus.

Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
---
 drivers/spi/spidev.c | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/drivers/spi/spidev.c b/drivers/spi/spidev.c
index e3c19f30f591..2e05046f866b 100644
--- a/drivers/spi/spidev.c
+++ b/drivers/spi/spidev.c
@@ -29,6 +29,7 @@
 #include <linux/compat.h>
 #include <linux/of.h>
 #include <linux/of_device.h>
+#include <linux/acpi.h>
 
 #include <linux/spi/spi.h>
 #include <linux/spi/spidev.h>
@@ -700,6 +701,43 @@ static const struct of_device_id spidev_dt_ids[] = {
 MODULE_DEVICE_TABLE(of, spidev_dt_ids);
 #endif
 
+#ifdef CONFIG_ACPI
+
+/* Dummy SPI devices not to be used in production systems */
+#define SPIDEV_ACPI_DUMMY	1
+
+static const struct acpi_device_id spidev_acpi_ids[] = {
+	/*
+	 * The ACPI SPT000* devices are only meant for development and
+	 * testing. Systems used in production should have a proper ACPI
+	 * description of the connected peripheral and they should also use
+	 * a proper driver instead of poking directly to the SPI bus.
+	 */
+	{ "SPT0001", SPIDEV_ACPI_DUMMY },
+	{ "SPT0002", SPIDEV_ACPI_DUMMY },
+	{ "SPT0003", SPIDEV_ACPI_DUMMY },
+	{},
+};
+MODULE_DEVICE_TABLE(acpi, spidev_acpi_ids);
+
+static void spidev_probe_acpi(struct spi_device *spi)
+{
+	const struct acpi_device_id *id;
+
+	if (!has_acpi_companion(&spi->dev))
+		return;
+
+	id = acpi_match_device(spidev_acpi_ids, &spi->dev);
+	if (WARN_ON(!id))
+		return;
+
+	if (id->driver_data == SPIDEV_ACPI_DUMMY)
+		dev_warn(&spi->dev, "do not use this driver in production systems!\n");
+}
+#else
+static inline void spidev_probe_acpi(struct spi_device *spi) {}
+#endif
+
 /*-------------------------------------------------------------------------*/
 
 static int spidev_probe(struct spi_device *spi)
@@ -719,6 +757,8 @@ static int spidev_probe(struct spi_device *spi)
 			!of_match_device(spidev_dt_ids, &spi->dev));
 	}
 
+	spidev_probe_acpi(spi);
+
 	/* Allocate driver data */
 	spidev = kzalloc(sizeof(*spidev), GFP_KERNEL);
 	if (!spidev)
@@ -789,6 +829,7 @@ static struct spi_driver spidev_spi_driver = {
 	.driver = {
 		.name =		"spidev",
 		.of_match_table = of_match_ptr(spidev_dt_ids),
+		.acpi_match_table = ACPI_PTR(spidev_acpi_ids),
 	},
 	.probe =	spidev_probe,
 	.remove =	spidev_remove,
-- 
2.8.1

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