Merge branch 'at91' into devel

[linux-2.6-omap-h63xx.git] / drivers / spi / spi.c

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 964124b60db2560b12f15d08dbdeeff43a058e16..75e86865234c924a67bb94d39c3fc259a6925b5a 100644 (file)
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -226,10 +226,11 @@ EXPORT_SYMBOL_GPL(spi_alloc_device);
  * Companion function to spi_alloc_device.  Devices allocated with
  * spi_alloc_device can be added onto the spi bus with this function.
  *
- * Returns 0 on success; non-zero on failure
+ * Returns 0 on success; negative errno on failure
  */
 int spi_add_device(struct spi_device *spi)
 {
+       static DEFINE_MUTEX(spi_add_lock);
        struct device *dev = spi->master->dev.parent;
        int status;
 
@@ -246,26 +247,43 @@ int spi_add_device(struct spi_device *spi)
                        "%s.%u", spi->master->dev.bus_id,
                        spi->chip_select);
 
-       /* drivers may modify this initial i/o setup */
+
+       /* We need to make sure there's no other device with this
+        * chipselect **BEFORE** we call setup(), else we'll trash
+        * its configuration.  Lock against concurrent add() calls.
+        */
+       mutex_lock(&spi_add_lock);
+
+       if (bus_find_device_by_name(&spi_bus_type, NULL, spi->dev.bus_id)
+                       != NULL) {
+               dev_err(dev, "chipselect %d already in use\n",
+                               spi->chip_select);
+               status = -EBUSY;
+               goto done;
+       }
+
+       /* Drivers may modify this initial i/o setup, but will
+        * normally rely on the device being setup.  Devices
+        * using SPI_CS_HIGH can't coexist well otherwise...
+        */
        status = spi->master->setup(spi);
        if (status < 0) {
                dev_err(dev, "can't %s %s, status %d\n",
                                "setup", spi->dev.bus_id, status);
-               return status;
+               goto done;
        }
 
-       /* driver core catches callers that misbehave by defining
-        * devices that already exist.
-        */
+       /* Device may be bound to an active driver when this returns */
        status = device_add(&spi->dev);
-       if (status < 0) {
+       if (status < 0)
                dev_err(dev, "can't %s %s, status %d\n",
                                "add", spi->dev.bus_id, status);
-               return status;
-       }
+       else
+               dev_dbg(dev, "registered child %s\n", spi->dev.bus_id);
 
-       dev_dbg(dev, "registered child %s\n", spi->dev.bus_id);
-       return 0;
+done:
+       mutex_unlock(&spi_add_lock);
+       return status;
 }
 EXPORT_SYMBOL_GPL(spi_add_device);