diff options
| -rw-r--r-- | drivers/spi/spi.c | 40 |
1 files changed, 29 insertions, 11 deletions
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 964124b60db..75e86865234 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); |