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authorMika Westerberg <mika.westerberg@linux.intel.com>2016-07-04 17:18:15 +0300
committerMark Brown <broonie@kernel.org>2016-07-04 16:28:52 +0200
commitcf9f4327a306be58df6c0b3817d7ef06a2a3da03 (patch)
tree5eef0fca251233c13da8fc04db14bad541a87dff /drivers/spi
parent1a695a905c18548062509178b98bc91e67510864 (diff)
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@linux.intel.com> Signed-off-by: Mark Brown <broonie@kernel.org>
Diffstat (limited to 'drivers/spi')
-rw-r--r--drivers/spi/spidev.c41
1 files changed, 41 insertions, 0 deletions
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,