Driver core: change add_uevent_var to use a struct

This changes the uevent buffer functions to use a struct instead of a
long list of parameters. It does no longer require the caller to do the
proper buffer termination and size accounting, which is currently wrong
in some places. It fixes a known bug where parts of the uevent
environment are overwritten because of wrong index calculations.

Many thanks to Mathieu Desnoyers for finding bugs and improving the
error handling.

Signed-off-by: Kay Sievers <kay.sievers@vrfy.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>


diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
index e84d215..bcb8dd5 100644
--- a/drivers/spi/spi.c
+++ b/drivers/spi/spi.c
@@ -67,14 +67,11 @@
 	return strncmp(spi->modalias, drv->name, BUS_ID_SIZE) == 0;
 }
 
-static int spi_uevent(struct device *dev, char **envp, int num_envp,
-		char *buffer, int buffer_size)
+static int spi_uevent(struct device *dev, struct kobj_uevent_env *env)
 {
 	const struct spi_device		*spi = to_spi_device(dev);
 
-	envp[0] = buffer;
-	snprintf(buffer, buffer_size, "MODALIAS=%s", spi->modalias);
-	envp[1] = NULL;
+	add_uevent_var(env, "MODALIAS=%s", spi->modalias);
 	return 0;
 }