i2c: use an IRQ to report Host Notify events, not alert

The current SMBus Host Notify implementation relies on .alert() to
relay its notifications. However, the use cases where SMBus Host
Notify is needed currently is to signal data ready on touchpads.

This is closer to an IRQ than a custom API through .alert().
Given that the 2 touchpad manufacturers (Synaptics and Elan) that
use SMBus Host Notify don't put any data in the SMBus payload, the
concept actually matches one to one.

Benefits are multiple:
- simpler code and API: the client will just have an IRQ, and
  nothing needs to be added in the adapter beside internally
  enabling it.
- no more specific workqueue, the threading is handled by IRQ core
  directly (when required)
- no more races when removing the device (the drivers are already
  required to disable irq on remove)
- simpler handling for drivers: use plain regular IRQs
- no more dependency on i2c-smbus for i2c-i801 (and any other adapter)
- the IRQ domain is created automatically when the adapter exports
  the Host Notify capability
- the IRQ are assign only if ACPI, OF and the caller did not assign
  one already
- the domain is automatically destroyed on remove
- fewer lines of code (minus 20, yeah!)

Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 7 insertions, 25 deletions

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index c0c0cac9950c..e242db43774b 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -269,7 +269,6 @@ struct i801_priv {
 	 */
 	bool acpi_reserved;
 	struct mutex acpi_lock;
-	struct smbus_host_notify *host_notify;
 };
 
 #define FEATURE_SMBUS_PEC	BIT(0)
@@ -585,10 +584,10 @@ static irqreturn_t i801_host_notify_isr(struct i801_priv *priv)
 
 	/*
 	 * With the tested platforms, reading SMBNTFDDAT (22 + (p)->smba)
-	 * always returns 0 and is safe to read.
-	 * We just use 0 given we have no use of the data right now.
+	 * always returns 0. Our current implementation doesn't provide
+	 * data, so we just ignore it.
 	 */
-	i2c_handle_smbus_host_notify(priv->host_notify, addr, 0);
+	i2c_handle_smbus_host_notify(&priv->adapter, addr);
 
 	/* clear Host Notify bit and return */
 	outb_p(SMBSLVSTS_HST_NTFY_STS, SMBSLVSTS(priv));
@@ -951,17 +950,12 @@ static u32 i801_func(struct i2c_adapter *adapter)
 		I2C_FUNC_SMBUS_HOST_NOTIFY : 0);
 }
 
-static int i801_enable_host_notify(struct i2c_adapter *adapter)
+static void i801_enable_host_notify(struct i2c_adapter *adapter)
 {
 	struct i801_priv *priv = i2c_get_adapdata(adapter);
 
 	if (!(priv->features & FEATURE_HOST_NOTIFY))
-		return -ENOTSUPP;
-
-	if (!priv->host_notify)
-		priv->host_notify = i2c_setup_smbus_host_notify(adapter);
-	if (!priv->host_notify)
-		return -ENOMEM;
+		return;
 
 	priv->original_slvcmd = inb_p(SMBSLVCMD(priv));
 
@@ -971,8 +965,6 @@ static int i801_enable_host_notify(struct i2c_adapter *adapter)
 
 	/* clear Host Notify bit to allow a new notification */
 	outb_p(SMBSLVSTS_HST_NTFY_STS, SMBSLVSTS(priv));
-
-	return 0;
 }
 
 static void i801_disable_host_notify(struct i801_priv *priv)
@@ -1647,14 +1639,7 @@ static int i801_probe(struct pci_dev *dev, const struct pci_device_id *id)
 		return err;
 	}
 
-	/*
-	 * Enable Host Notify for chips that supports it.
-	 * It is done after i2c_add_adapter() so that we are sure the work queue
-	 * is not used if i2c_add_adapter() fails.
-	 */
-	err = i801_enable_host_notify(&priv->adapter);
-	if (err && err != -ENOTSUPP)
-		dev_warn(&dev->dev, "Unable to enable SMBus Host Notify\n");
+	i801_enable_host_notify(&priv->adapter);
 
 	i801_probe_optional_slaves(priv);
 	/* We ignore errors - multiplexing is optional */
@@ -1705,11 +1690,8 @@ static int i801_resume(struct device *dev)
 {
 	struct pci_dev *pci_dev = to_pci_dev(dev);
 	struct i801_priv *priv = pci_get_drvdata(pci_dev);
-	int err;
 
-	err = i801_enable_host_notify(&priv->adapter);
-	if (err && err != -ENOTSUPP)
-		dev_warn(dev, "Unable to enable SMBus Host Notify\n");
+	i801_enable_host_notify(&priv->adapter);
 
 	return 0;
 }