mfd: tps6105x: Fix possible NULL pointer access

tps6105 driver provides two cells. One is for GPIO and another one is
for selected mode depending on platform data. When tps6105x is used in
GPIO-only mode, this driver calls mfd_add_devices() with mfd_cell
.name == NULL. This value causes an oops in platform_device_register()
later.

The following patch adds a mfd_cell for each possible mode thereby
excluding .name assignment in runtime.
Signed-off-by: Denis Grigoryev <grigoryev@fastwel.ru>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/tps6105x.c

@@ -64,27 +64,47 @@ static int tps6105x_startup(struct tps6105x *tps6105x)
 }
 
 /*
- * MFD cells - we have one cell which is selected operation
- * mode, and we always have a GPIO cell.
+ * MFD cells - we always have a GPIO cell and we have one cell
+ * which is selected operation mode.
  */
-static struct mfd_cell tps6105x_cells[] = {
-	{
-		/* name will be runtime assigned */
-		.id = -1,
-	},
-	{
-		.name = "tps6105x-gpio",
-		.id = -1,
-	},
+static struct mfd_cell tps6105x_gpio_cell = {
+	.name = "tps6105x-gpio",
+};
+
+static struct mfd_cell tps6105x_leds_cell = {
+	.name = "tps6105x-leds",
+};
+
+static struct mfd_cell tps6105x_flash_cell = {
+	.name = "tps6105x-flash",
 };
 
+static struct mfd_cell tps6105x_regulator_cell = {
+	.name = "tps6105x-regulator",
+};
+
+static int tps6105x_add_device(struct tps6105x *tps6105x,
+			       struct mfd_cell *cell)
+{
+	cell->platform_data = tps6105x;
+	cell->pdata_size = sizeof(*tps6105x);
+
+	return mfd_add_devices(&tps6105x->client->dev,
+			       PLATFORM_DEVID_AUTO, cell, 1, NULL, 0, NULL);
+}
+
 static int tps6105x_probe(struct i2c_client *client,
 			const struct i2c_device_id *id)
 {
 	struct tps6105x			*tps6105x;
 	struct tps6105x_platform_data	*pdata;
 	int ret;
-	int i;
+
+	pdata = dev_get_platdata(&client->dev);
+	if (!pdata) {
+		dev_err(&client->dev, "missing platform data\n");
+		return -ENODEV;
+	}
 
 	tps6105x = devm_kmalloc(&client->dev, sizeof(*tps6105x), GFP_KERNEL);
 	if (!tps6105x)
@@ -96,7 +116,6 @@ static int tps6105x_probe(struct i2c_client *client,
 
 	i2c_set_clientdata(client, tps6105x);
 	tps6105x->client = client;
-	pdata = dev_get_platdata(&client->dev);
 	tps6105x->pdata = pdata;
 
 	ret = tps6105x_startup(tps6105x);
@@ -105,38 +124,33 @@ static int tps6105x_probe(struct i2c_client *client,
 		return ret;
 	}
 
-	/* Remove warning texts when you implement new cell drivers */
+	ret = tps6105x_add_device(tps6105x, &tps6105x_gpio_cell);
+	if (ret)
+		return ret;
+
 	switch (pdata->mode) {
 	case TPS6105X_MODE_SHUTDOWN:
 		dev_info(&client->dev,
 			 "present, not used for anything, only GPIO\n");
 		break;
 	case TPS6105X_MODE_TORCH:
-		tps6105x_cells[0].name = "tps6105x-leds";
-		dev_warn(&client->dev,
-			 "torch mode is unsupported\n");
+		ret = tps6105x_add_device(tps6105x, &tps6105x_leds_cell);
 		break;
 	case TPS6105X_MODE_TORCH_FLASH:
-		tps6105x_cells[0].name = "tps6105x-flash";
-		dev_warn(&client->dev,
-			 "flash mode is unsupported\n");
+		ret = tps6105x_add_device(tps6105x, &tps6105x_flash_cell);
 		break;
 	case TPS6105X_MODE_VOLTAGE:
-		tps6105x_cells[0].name ="tps6105x-regulator";
+		ret = tps6105x_add_device(tps6105x, &tps6105x_regulator_cell);
 		break;
 	default:
+		dev_warn(&client->dev, "invalid mode: %d\n", pdata->mode);
 		break;
 	}
 
-	/* Set up and register the platform devices. */
-	for (i = 0; i < ARRAY_SIZE(tps6105x_cells); i++) {
-		/* One state holder for all drivers, this is simple */
-		tps6105x_cells[i].platform_data = tps6105x;
-		tps6105x_cells[i].pdata_size = sizeof(*tps6105x);
-	}
+	if (ret)
+		mfd_remove_devices(&client->dev);
 
-	return mfd_add_devices(&client->dev, 0, tps6105x_cells,
-			       ARRAY_SIZE(tps6105x_cells), NULL, 0, NULL);
+	return ret;
 }
 
 static int tps6105x_remove(struct i2c_client *client)