drivers:seco-stm32.c: some info about stm32 made available through sysfs

 - firmware version and chip-id of the stm32 can be read from sysfs
 - in difference to other gpio controlers the stm32 can serve as interrupt-
   controler without having gpios configured

drivers/staging/mfd/seco-stm32.c

@@ -45,6 +45,7 @@ struct stm32 {
 	struct mutex lock;
 	int irq_base;
 	int irq_map[STM32_IRQ_MAX];
+	unsigned char chip_id, fw_ver;
 	//unsigned int irq_mask;
 	//struct mutex i2c_lock;
 	//struct mutex irq_lock;
@@ -466,6 +467,27 @@ static void stm32_irq_flow_handler(struct irq_desc *desc)
 }
 #endif
 
+
+// sysfs
+// can be found in /sys/bus/i2c/devices/b-aaaa
+// were b is the bus number and aaaa is the address in hex
+static ssize_t fw_ver_show(struct device *dev,
+						   struct device_attribute *attr, char *buf)
+{
+	struct stm32 *stm32=dev_get_drvdata(dev);
+	return sprintf(buf, "0x%02hhx\n",stm32->fw_ver);
+}
+static DEVICE_ATTR_RO(fw_ver);
+
+static ssize_t chip_id_show(struct device *dev,
+							struct device_attribute *attr, char *buf)
+{
+	struct stm32 *stm32=dev_get_drvdata(dev);
+	return sprintf(buf, "0x%02hhx\n",stm32->chip_id);
+}
+static DEVICE_ATTR_RO(chip_id);
+
+
 // parse the device tree
 //static int stm32_parse_dt(struct device *dev, struct stm32 *stm32)
 static int stm32_parse_dt(struct i2c_client *client, struct stm32 *stm32)
@@ -598,6 +620,13 @@ static int stm32_probe(struct i2c_client *client,
 	struct stm32 *stm32;
 
 	dev_info(dev,"%s\n", __FUNCTION__);
+
+	// allocate memory for private data
+	stm32=devm_kzalloc(dev, sizeof(*stm32), GFP_KERNEL);
+	if(!stm32)
+		return -ENOMEM;
+	stm32->pwm_chip.dev=dev;
+
 	// read the chip id
 	err=i2c_xfer(client, STM32_READ, STM32_REG_ID, 0);
 	if(err < 0)
@@ -612,6 +641,7 @@ static int stm32_probe(struct i2c_client *client,
 		dev_err(dev, "%s: invalid chip id (0x%02x)\n", __FUNCTION__, err);
 		return -ENOENT;
 	}
+	stm32->chip_id=(unsigned char)err;
 	dev_info(dev, "%s: chip id: 0x%02x\n", __FUNCTION__, err);
 
 	// read firmware version
@@ -622,19 +652,15 @@ static int stm32_probe(struct i2c_client *client,
 				__FUNCTION__, err);
 		return err;
 	}
+	stm32->fw_ver=(unsigned char)err;
 	dev_info(dev,"%s: firmware 0x%02x\n", __FUNCTION__, err);
 
-	// allocate memory for private data and fill it from the device tree
-	stm32=devm_kzalloc(dev, sizeof(*stm32), GFP_KERNEL);
-	if(!stm32)
-		return -ENOMEM;
-
-	stm32->pwm_chip.dev=dev;
+	// fill private data from the device tree
 	err=stm32_parse_dt(client, stm32);
 	if(err)
 		return err;
 
-	if(!stm32->pwm_chip.npwm && !stm32->gpio_chip.ngpio)
+	if(!stm32->pwm_chip.npwm && !stm32->gpio_chip.ngpio && !client->irq)
 		return -ENOENT;
 	mutex_init(&stm32->lock);
 	dev_set_drvdata(dev, stm32);
@@ -695,6 +721,10 @@ static int stm32_probe(struct i2c_client *client,
 			return err;
 	}
 
+	// add sysfs entries
+	device_create_file(dev, &dev_attr_chip_id);
+	device_create_file(dev, &dev_attr_fw_ver);
+
 	dev_info(dev, "%s: OK\n", __FUNCTION__);
 
 	return 0;