Add a sysfs interface to instantiate and delete SPI devices using the
spidev driver. This can be used when developing a driver on a
self-soldered board which doesn't yet have proper SPI device declaration
at the platform level, and presumably for various debugging situations.
Inspired by 99cd8e25875a ("i2c: Add a sysfs interface to instantiate
devices").
Signed-off-by: Kyle Roeschley <kyle.roesch...@ni.com>
---
Documentation/spi/spi-summary | 14 ++++++++
drivers/spi/spi.c | 78 +++++++++++++++++++++++++++++++++++++++++++
include/linux/spi/spi.h | 3 ++
3 files changed, 95 insertions(+)
diff --git a/Documentation/spi/spi-summary b/Documentation/spi/spi-summary
index 1721c1b570c3..51d9747c4426 100644
--- a/Documentation/spi/spi-summary
+++ b/Documentation/spi/spi-summary
@@ -339,6 +339,20 @@ up the spi bus master, and will likely need
spi_new_device() to provide the
board info based on the board that was hotplugged. Of course, you'd later
call at least spi_unregister_device() when that board is removed.
+Alternatively, a sysfs interface was added to let the user create devices which
+using the spidev driver. This interface is made of 2 attribute files which are
+created in every SPI master directory: new_device and delete_device. Both files
+are write only and you must write the decimal SPI chip select number to them in
+order to properly instantiate or delete a SPI device. As no two devices can be
+attached to the same master with the same chip select line, the chip select
+number is sufficient to uniquely identify the device to be deleted.
+
+Example:
+# echo 1 > /sys/class/spi_master/spi0/new_device
+
+In general, this interface should only be used when in-kernel device
+declaration can't be done.
+
When Linux includes support for MMC/SD/SDIO/DataFlash cards through SPI, those
configurations will also be dynamic. Fortunately, such devices all support
basic device identification probes, so they should hotplug normally.
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index b33a727a0158..648ccdf359f9 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -242,8 +242,85 @@ static const struct attribute_group
spi_controller_statistics_group = {
.attrs = spi_controller_statistics_attrs,
};
+static ssize_t
+new_device_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct spi_controller *ctlr = container_of(dev, struct spi_controller,
+ dev);
+ struct spi_device *spi;
+ struct spi_board_info bi = {
+ .modalias = "spidev",
+ .max_speed_hz = ctlr->max_speed_hz,
+ };
+
+ if (kstrtou16(buf, 0, &bi.chip_select) < 0)
+ return -EINVAL;
+
+ spi = spi_new_device(ctlr, &bi);
+ if (!spi) {
+ dev_err(dev, "can't create new device\n");
+ return -ENXIO;
+ }
+
+ mutex_lock(&ctlr->bus_lock_mutex);
+ list_add_tail(&spi->userspace_device, &ctlr->userspace_devices);
+ mutex_unlock(&ctlr->bus_lock_mutex);
+
+ dev_info(dev, "created spidev device %s\n", dev_name(&spi->dev));
+
+ return count;
+}
+static DEVICE_ATTR_WO(new_device);
+
+static ssize_t
+delete_device_store(struct device *dev, struct device_attribute *attr,
+ const char *buf, size_t count)
+{
+ struct spi_controller *ctlr = container_of(dev, struct spi_controller,
+ dev);
+ struct spi_device *spi, *next;
+ int ret = -ENXIO;
+ u16 cs;
+
+ if (kstrtou16(buf, 0, &cs) < 0)
+ return -EINVAL;
+
+ mutex_lock(&ctlr->bus_lock_mutex);
+ list_for_each_entry_safe(spi, next, &ctlr->userspace_devices,
+ userspace_device) {
+ if (spi->chip_select != cs)
+ continue;
+
+ dev_info(dev, "deleting spidev device %s\n",
+ dev_name(&spi->dev));
+ list_del(&spi->userspace_device);
+ spi_unregister_device(spi);
+ ret = count;
+ break;
+ }
+ mutex_unlock(&ctlr->bus_lock_mutex);
+
+ if (ret == -ENXIO)
+ dev_err(dev, "can't find spidev device %u in list\n", cs);
+
+ return ret;
+}
+static DEVICE_ATTR_WO(delete_device);
+
+static struct attribute *spi_controller_userspace_attrs[] = {
+ &dev_attr_new_device.attr,
+ &dev_attr_delete_device.attr,
+ NULL,
+};
+
+static const struct attribute_group spi_controller_userspace_group = {
+ .attrs = spi_controller_userspace_attrs,
+};
+
static const struct attribute_group *spi_master_groups[] = {
&spi_controller_statistics_group,
+ &spi_controller_userspace_group,
NULL,
};
@@ -2129,6 +2206,7 @@ int spi_register_controller(struct spi_controller *ctlr)
return id;
ctlr->bus_num = id;
}
+ INIT_LIST_HEAD(&ctlr->userspace_devices);
INIT_LIST_HEAD(&ctlr->queue);
spin_lock_init(&ctlr->queue_lock);
spin_lock_init(&ctlr->bus_lock_spinlock);
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index bc6bb325d1bf..f7255745326d 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -172,6 +172,8 @@ struct spi_device {
/* the statistics */
struct spi_statistics statistics;
+ struct list_head userspace_device;
+
/*
* likely need more hooks for more protocol options affecting how
* the controller talks to each chip, like:
@@ -410,6 +412,7 @@ struct spi_controller {
struct device dev;
struct list_head list;
+ struct list_head userspace_devices;
/* other than negative (== assign one dynamically), bus_num is fully
* board-specific. usually that simplifies to being SOC-specific.
--
2.15.1
