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-rw-r--r--drivers/spi/spi.c40
1 files changed, 29 insertions, 11 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 964124b60db2..75e86865234c 100644
--- 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);

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