1 files changed, 4 insertions, 3 deletions

diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index 94f5e8ed83a7..7a3f733051e9 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -395,7 +395,7 @@ EXPORT_SYMBOL_GPL(spi_alloc_master);
 int __init_or_module
 spi_register_master(struct spi_master *master)
 {
-        static atomic_t         dyn_bus_id = ATOMIC_INIT(0);
+        static atomic_t         dyn_bus_id = ATOMIC_INIT((1<<16) - 1);
         struct device           *dev = master->cdev.dev;
         int                     status = -ENODEV;
         int                     dynamic = 0;
@@ -404,7 +404,7 @@ spi_register_master(struct spi_master *master)
                 return -ENODEV;
 
         /* convention:  dynamically assigned bus IDs count down from the max */
-        if (master->bus_num == 0) {
+        if (master->bus_num < 0) {
                 master->bus_num = atomic_dec_return(&dyn_bus_id);
                 dynamic = 1;
         }
@@ -522,7 +522,8 @@ int spi_sync(struct spi_device *spi, struct spi_message *message)
 }
 EXPORT_SYMBOL_GPL(spi_sync);
 
-#define SPI_BUFSIZ      (SMP_CACHE_BYTES)
+/* portable code must never pass more than 32 bytes */
+#define SPI_BUFSIZ      max(32,SMP_CACHE_BYTES)
 
 static u8       *buf;