[1/5] spi: spi_lock_bus and spi_unlock_bus

Commit Message

Ernst Schwab Feb. 16, 2010, 7:57 p.m. UTC

None

Patch

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 70845cc..b82b8ad 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -653,6 +653,54 @@  static void spi_complete(void *arg)
 }
 
 /**
+ * spi_lock_bus - lock SPI bus for exclusive access
+ * @spi: device which want to lock the bus
+ * Context: any
+ *
+ * Once the caller owns exclusive access to the SPI bus,
+ * only messages for this device will be transferred.
+ * Messages for other devices are queued but not transferred until
+ * the bus owner unlock the bus.
+ *
+ * The caller may call spi_lock_bus() before spi_sync() or spi_async().
+ * So this call may be used in irq and other contexts which can't sleep,
+ * as well as from task contexts which can sleep.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_lock_bus(struct spi_device *spi)
+{
+	if (spi->master->lock_bus)
+		return spi->master->lock_bus(spi);
+	else
+		return 0;
+}
+EXPORT_SYMBOL_GPL(spi_lock_bus);
+
+/**
+ * spi_unlock_bus - unlock SPI bus
+ * @spi: device which want to unlock the bus
+ * Context: any
+ *
+ * The caller has called spi_lock_bus() to lock the bus. It calls
+ * spi_unlock_bus() to release the bus so messages for other devices
+ * can be transferred.
+ *
+ * If the caller did not call spi_lock_bus() before, spi_unlock_bus()
+ * should have no effect.
+ *
+ * It returns zero on success, else a negative error code.
+ */
+int spi_unlock_bus(struct spi_device *spi)
+{
+	if (spi->master->unlock_bus)
+		return spi->master->unlock_bus(spi);
+	else
+		return 0;
+}
+EXPORT_SYMBOL_GPL(spi_unlock_bus);
+
+/**
  * spi_sync - blocking/synchronous SPI data transfers
  * @spi: device with which data will be exchanged
  * @message: describes the data transfers
diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h
index c47c4b4..c53292c 100644
--- a/include/linux/spi/spi.h
+++ b/include/linux/spi/spi.h
@@ -214,6 +214,8 @@  static inline void spi_unregister_driver(struct spi_driver *sdrv)
  *	the device whose settings are being modified.
  * @transfer: adds a message to the controller's transfer queue.
  * @cleanup: frees controller-specific state
+ * @lock_bus: lock SPI bus for exclusive access
+ * @unlock_bus: unlock SPI bus so other devices can access
  *
  * Each SPI master controller can communicate with one or more @spi_device
  * children.  These make a small bus, sharing MOSI, MISO and SCK signals
@@ -286,6 +288,9 @@  struct spi_master {
 
 	/* called on release() to free memory provided by spi_master */
 	void			(*cleanup)(struct spi_device *spi);
+
+	int			(*lock_bus)(struct spi_device *spi);
+	int			(*unlock_bus)(struct spi_device *spi);
 };
 
 static inline void *spi_master_get_devdata(struct spi_master *master)
@@ -578,6 +583,8 @@  spi_async(struct spi_device *spi, struct spi_message *message)
  */
 
 extern int spi_sync(struct spi_device *spi, struct spi_message *message);
+extern int spi_lock_bus(struct spi_device *spi);
+extern int spi_unlock_bus(struct spi_device *spi);
 
 /**
  * spi_write - SPI synchronous write