gpio: pca953x handles more chips, i2c fault codes

Minor updates to the pca953x GPIO expander driver: handle several more
compatible parts, and stop assuming that the I2C layer's return codes are
garbage (that's now been fixed).

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Eric Miao <eric.miao@marvell.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/gpio/Kconfig

@@ -95,7 +95,7 @@ config GPIO_MAX732X
 	  number for these GPIOs.
 
 config GPIO_PCA953X
-	tristate "PCA953x, PCA955x, and MAX7310 I/O ports"
+	tristate "PCA953x, PCA955x, TCA64xx, and MAX7310 I/O ports"
 	depends on I2C
 	help
 	  Say yes here to provide access to several register-oriented
@@ -104,9 +104,10 @@ config GPIO_PCA953X
 
 	  4 bits:	pca9536, pca9537
 
-	  8 bits:	max7310, pca9534, pca9538, pca9554, pca9557
+	  8 bits:	max7310, pca9534, pca9538, pca9554, pca9557,
+	  		tca6408
 
-	  16 bits:	pca9535, pca9539, pca9555
+	  16 bits:	pca9535, pca9539, pca9555, tca6416
 
 	  This driver can also be built as a module.  If so, the module
 	  will be called pca953x.

drivers/gpio/pca953x.c

@@ -33,7 +33,12 @@ static const struct i2c_device_id pca953x_id[] = {
 	{ "pca9554", 8, },
 	{ "pca9555", 16, },
 	{ "pca9557", 8, },
+
 	{ "max7310", 8, },
+	{ "pca6107", 8, },
+	{ "tca6408", 8, },
+	{ "tca6416", 16, },
+	/* NYET:  { "tca6424", 24, }, */
 	{ }
 };
 MODULE_DEVICE_TABLE(i2c, pca953x_id);
@@ -47,9 +52,6 @@ struct pca953x_chip {
 	struct gpio_chip gpio_chip;
 };
 
-/* NOTE:  we can't currently rely on fault codes to come from SMBus
- * calls, so we map all errors to EIO here and return zero otherwise.
- */
 static int pca953x_write_reg(struct pca953x_chip *chip, int reg, uint16_t val)
 {
 	int ret;
@@ -61,7 +63,7 @@ static int pca953x_write_reg(struct pca953x_chip *chip, int reg, uint16_t val)
 
 	if (ret < 0) {
 		dev_err(&chip->client->dev, "failed writing register\n");
-		return -EIO;
+		return ret;
 	}
 
 	return 0;
@@ -78,7 +80,7 @@ static int pca953x_read_reg(struct pca953x_chip *chip, int reg, uint16_t *val)
 
 	if (ret < 0) {
 		dev_err(&chip->client->dev, "failed reading register\n");
-		return -EIO;
+		return ret;
 	}
 
 	*val = (uint16_t)ret;