gpio: fix probe() error return in gpio driver probes

A number of drivers in drivers/gpio return -ENODEV when confronted with
missing setup parameters such as the platform data.  However, returning
-ENODEV causes the driver layer to silently ignore the driver as it
assumes the probe did not find anything and was only speculative.

To make life easier to discern why a driver is not being attached, change
to returning -EINVAL, which is a better description of the fact that the
driver data was not valid.

Also add a set of dev_dbg() statements to the error paths to provide an
better explanation of the error as there may be more that one point in the
driver.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/gpio/mcp23s08.c b/drivers/gpio/mcp23s08.c
index 89c1d22..f6fae0e 100644
--- a/drivers/gpio/mcp23s08.c
+++ b/drivers/gpio/mcp23s08.c
@@ -310,8 +310,10 @@ static int mcp23s08_probe(struct spi_device *spi)
 	unsigned			base;
 
 	pdata = spi->dev.platform_data;
-	if (!pdata || !gpio_is_valid(pdata->base))
-		return -ENODEV;
+	if (!pdata || !gpio_is_valid(pdata->base)) {
+		dev_dbg(&spi->dev, "invalid or missing platform data\n");
+		return -EINVAL;
+	}
 
 	for (addr = 0; addr < 4; addr++) {
 		if (!pdata->chip[addr].is_present)