+/*
+ * Update the readings from the GPIO pins. If the driver has been configured to
+ * sample all GPIO's as analog voltages, a round-robin sampling method is used.
+ * Otherwise, only the configured GPIO pin is sampled.
+ *
+ * LOCKING: must hold data->update_lock
+ */
+static void ltc4245_update_gpios(struct device *dev)
+{
+ struct i2c_client *client = to_i2c_client(dev);
+ struct ltc4245_data *data = i2c_get_clientdata(client);
+ u8 gpio_curr, gpio_next, gpio_reg;
+ int i;
+
+ /* no extra gpio support, we're basically done */
+ if (!data->use_extra_gpios) {
+ data->gpios[0] = data->vregs[LTC4245_GPIOADC - 0x10];
+ return;
+ }
+
+ /*
+ * If the last reading was too long ago, then we mark all old GPIO
+ * readings as stale by setting them to -EAGAIN
+ */
+ if (time_after(jiffies, data->last_updated + 5 * HZ)) {
+ dev_dbg(&client->dev, "Marking GPIOs invalid\n");
+ for (i = 0; i < ARRAY_SIZE(data->gpios); i++)
+ data->gpios[i] = -EAGAIN;
+ }
+
+ /*
+ * Get the current GPIO pin
+ *
+ * The datasheet calls these GPIO[1-3], but we'll calculate the zero
+ * based array index instead, and call them GPIO[0-2]. This is much
+ * easier to think about.
+ */
+ gpio_curr = (data->cregs[LTC4245_GPIO] & 0xc0) >> 6;
+ if (gpio_curr > 0)
+ gpio_curr -= 1;
+
+ /* Read the GPIO voltage from the GPIOADC register */
+ data->gpios[gpio_curr] = data->vregs[LTC4245_GPIOADC - 0x10];
+
+ /* Find the next GPIO pin to read */
+ gpio_next = (gpio_curr + 1) % ARRAY_SIZE(data->gpios);
+
+ /*
+ * Calculate the correct setting for the GPIO register so it will
+ * sample the next GPIO pin
+ */
+ gpio_reg = (data->cregs[LTC4245_GPIO] & 0x3f) | ((gpio_next + 1) << 6);
+
+ /* Update the GPIO register */
+ i2c_smbus_write_byte_data(client, LTC4245_GPIO, gpio_reg);
+
+ /* Update saved data */
+ data->cregs[LTC4245_GPIO] = gpio_reg;
+}
+