Input: libps2 - introduce common interrupt handler

Instead of exposing inner workings of libps2 to drivers such as atkbd and
psmouse, have them define pre-receive and receive callbacks, and provide a
common handler that can be used with underlying serio port.

While at this add kerneldoc to the module.

Link: https://lore.kernel.org/r/ZGK81cxqjr/KS1kA@google.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

1 files changed, 161 insertions, 65 deletions

diff --git a/drivers/input/serio/libps2.c b/drivers/input/serio/libps2.c
index 09eb605364bb..7c5fc853072a 100644
--- a/drivers/input/serio/libps2.c
+++ b/drivers/input/serio/libps2.c
@@ -19,9 +19,22 @@
 
 #define DRIVER_DESC	"PS/2 driver library"
 
-MODULE_AUTHOR("Dmitry Torokhov <dtor@mail.ru>");
-MODULE_DESCRIPTION("PS/2 driver library");
-MODULE_LICENSE("GPL");
+#define PS2_CMD_SETSCALE11	0x00e6
+#define PS2_CMD_SETRES		0x10e8
+#define PS2_CMD_GETID		0x02f2
+#define PS2_CMD_RESET_BAT	0x02ff
+
+#define PS2_RET_BAT		0xaa
+#define PS2_RET_ID		0x00
+#define PS2_RET_ACK		0xfa
+#define PS2_RET_NAK		0xfe
+#define PS2_RET_ERR		0xfc
+
+#define PS2_FLAG_ACK		BIT(0)	/* Waiting for ACK/NAK */
+#define PS2_FLAG_CMD		BIT(1)	/* Waiting for a command to finish */
+#define PS2_FLAG_CMD1		BIT(2)	/* Waiting for the first byte of command response */
+#define PS2_FLAG_WAITID		BIT(3)	/* Command executing is GET ID */
+#define PS2_FLAG_NAK		BIT(4)	/* Last transmission was NAKed */
 
 static int ps2_do_sendbyte(struct ps2dev *ps2dev, u8 byte,
 			   unsigned int timeout, unsigned int max_attempts)
@@ -76,14 +89,17 @@ static int ps2_do_sendbyte(struct ps2dev *ps2dev, u8 byte,
 	return error;
 }
 
-/*
- * ps2_sendbyte() sends a byte to the device and waits for acknowledge.
- * It doesn't handle retransmission, the caller is expected to handle
+/**
+ * ps2_sendbyte - sends a byte to the device and wait for acknowledgement
+ * @ps2dev: a PS/2 device to send the data to
+ * @byte: data to be sent to the device
+ * @timeout: timeout for sending the data and receiving an acknowledge
+ *
+ * The function doesn't handle retransmission, the caller is expected to handle
  * it when needed.
  *
  * ps2_sendbyte() can only be called from a process context.
  */
-
 int ps2_sendbyte(struct ps2dev *ps2dev, u8 byte, unsigned int timeout)
 {
 	int retval;
@@ -99,6 +115,13 @@ int ps2_sendbyte(struct ps2dev *ps2dev, u8 byte, unsigned int timeout)
 }
 EXPORT_SYMBOL(ps2_sendbyte);
 
+/**
+ * ps2_begin_command - mark beginning of execution of a complex command
+ * @ps2dev: a PS/2 device executing the command
+ *
+ * Serializes a complex/compound command. Once command is finished
+ * ps2_end_command() should be called.
+ */
 void ps2_begin_command(struct ps2dev *ps2dev)
 {
 	struct mutex *m = ps2dev->serio->ps2_cmd_mutex ?: &ps2dev->cmd_mutex;
@@ -107,6 +130,10 @@ void ps2_begin_command(struct ps2dev *ps2dev)
 }
 EXPORT_SYMBOL(ps2_begin_command);
 
+/**
+ * ps2_end_command - mark end of execution of a complex command
+ * @ps2dev: a PS/2 device executing the command
+ */
 void ps2_end_command(struct ps2dev *ps2dev)
 {
 	struct mutex *m = ps2dev->serio->ps2_cmd_mutex ?: &ps2dev->cmd_mutex;
@@ -115,11 +142,13 @@ void ps2_end_command(struct ps2dev *ps2dev)
 }
 EXPORT_SYMBOL(ps2_end_command);
 
-/*
- * ps2_drain() waits for device to transmit requested number of bytes
- * and discards them.
+/**
+ * ps2_drain - waits for device to transmit requested number of bytes
+ * and discards them
+ * @ps2dev: the PS/2 device that should be drained
+ * @maxbytes: maximum number of bytes to be drained
+ * @timeout: time to drain the device
  */
-
 void ps2_drain(struct ps2dev *ps2dev, size_t maxbytes, unsigned int timeout)
 {
 	if (maxbytes > sizeof(ps2dev->cmdbuf)) {
@@ -142,11 +171,11 @@ void ps2_drain(struct ps2dev *ps2dev, size_t maxbytes, unsigned int timeout)
 }
 EXPORT_SYMBOL(ps2_drain);
 
-/*
- * ps2_is_keyboard_id() checks received ID byte against the list of
- * known keyboard IDs.
+/**
+ * ps2_is_keyboard_id - checks received ID byte against the list of
+ *   known keyboard IDs
+ * @id_byte: data byte that should be checked
  */
-
 bool ps2_is_keyboard_id(u8 id_byte)
 {
 	static const u8 keyboard_ids[] = {
@@ -167,7 +196,6 @@ EXPORT_SYMBOL(ps2_is_keyboard_id);
  * response and tries to reduce remaining timeout to speed up command
  * completion.
  */
-
 static int ps2_adjust_timeout(struct ps2dev *ps2dev,
 			      unsigned int command, unsigned int timeout)
 {
@@ -217,13 +245,19 @@ static int ps2_adjust_timeout(struct ps2dev *ps2dev,
 	return timeout;
 }
 
-/*
- * ps2_command() sends a command and its parameters to the mouse,
- * then waits for the response and puts it in the param array.
+/**
+ * __ps2_command - send a command to PS/2 device
+ * @ps2dev: the PS/2 device that should execute the command
+ * @param: a buffer containing parameters to be sent along with the command,
+ *   or place where the results of the command execution will be deposited,
+ *   or both
+ * @command: command word that encodes the command itself, as well as number of
+ *   additional parameter bytes that should be sent to the device and expected
+ *   length of the command response
  *
- * ps2_command() can only be called from a process context
+ * Not serialized. Callers should use ps2_begin_command() and ps2_end_command()
+ * to ensure proper serialization for complex commands.
  */
-
 int __ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)
 {
 	unsigned int timeout;
@@ -327,6 +361,20 @@ int __ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)
 }
 EXPORT_SYMBOL(__ps2_command);
 
+/**
+ * ps2_command - send a command to PS/2 device
+ * @ps2dev: the PS/2 device that should execute the command
+ * @param: a buffer containing parameters to be sent along with the command,
+ *   or place where the results of the command execution will be deposited,
+ *   or both
+ * @command: command word that encodes the command itself, as well as number of
+ *   additional parameter bytes that should be sent to the device and expected
+ *   length of the command response
+ *
+ * Note: ps2_command() serializes the command execution so that only one
+ * command can be executed at a time for either individual port or the entire
+ * 8042 controller.
+ */
 int ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)
 {
 	int rc;
@@ -339,14 +387,16 @@ int ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)
 }
 EXPORT_SYMBOL(ps2_command);
 
-/*
- * ps2_sliced_command() sends an extended PS/2 command to the mouse
- * using sliced syntax, understood by advanced devices, such as Logitech
- * or Synaptics touchpads. The command is encoded as:
+/**
+ * ps2_sliced_command - sends an extended PS/2 command to a mouse
+ * @ps2dev: the PS/2 device that should execute the command
+ * @command: command byte
+ *
+ * The command is sent using "sliced" syntax understood by advanced devices,
+ * such as Logitech or Synaptics touchpads. The command is encoded as:
  * 0xE6 0xE8 rr 0xE8 ss 0xE8 tt 0xE8 uu where (rr*64)+(ss*16)+(tt*4)+uu
  * is the command.
  */
-
 int ps2_sliced_command(struct ps2dev *ps2dev, u8 command)
 {
 	int i;
@@ -372,12 +422,22 @@ out:
 }
 EXPORT_SYMBOL(ps2_sliced_command);
 
-/*
- * ps2_init() initializes ps2dev structure
+/**
+ * ps2_init - initializes ps2dev structure
+ * @ps2dev: structure to be initialized
+ * @serio: serio port associated with the PS/2 device
+ * @pre_receive_handler: validation handler to check basic communication state
+ * @receive_handler: main protocol handler
+ *
+ * Prepares ps2dev structure for use in drivers for PS/2 devices.
  */
-
-void ps2_init(struct ps2dev *ps2dev, struct serio *serio)
+void ps2_init(struct ps2dev *ps2dev, struct serio *serio,
+	      ps2_pre_receive_handler_t pre_receive_handler,
+	      ps2_receive_handler_t receive_handler)
 {
+	ps2dev->pre_receive_handler = pre_receive_handler;
+	ps2dev->receive_handler = receive_handler;
+
 	mutex_init(&ps2dev->cmd_mutex);
 	lockdep_set_subclass(&ps2dev->cmd_mutex, serio->depth);
 	init_waitqueue_head(&ps2dev->wait);
@@ -387,11 +447,35 @@ void ps2_init(struct ps2dev *ps2dev, struct serio *serio)
 EXPORT_SYMBOL(ps2_init);
 
 /*
- * ps2_handle_ack() is supposed to be used in interrupt handler
- * to properly process ACK/NAK of a command from a PS/2 device.
+ * ps2_handle_response() stores device's response to a command and notifies
+ * the process waiting for completion of the command. Note that there is a
+ * distinction between waiting for the first byte of the response, and
+ * waiting for subsequent bytes. It is done so that callers could shorten
+ * timeouts once first byte of response is received.
  */
+static void ps2_handle_response(struct ps2dev *ps2dev, u8 data)
+{
+	if (ps2dev->cmdcnt)
+		ps2dev->cmdbuf[--ps2dev->cmdcnt] = data;
 
-bool ps2_handle_ack(struct ps2dev *ps2dev, u8 data)
+	if (ps2dev->flags & PS2_FLAG_CMD1) {
+		ps2dev->flags &= ~PS2_FLAG_CMD1;
+		if (ps2dev->cmdcnt)
+			wake_up(&ps2dev->wait);
+	}
+
+	if (!ps2dev->cmdcnt) {
+		ps2dev->flags &= ~PS2_FLAG_CMD;
+		wake_up(&ps2dev->wait);
+	}
+}
+
+/*
+ * ps2_handle_ack() processes ACK/NAK of a command from a PS/2 device,
+ * possibly applying workarounds for mice not acknowledging the "get ID"
+ * command.
+ */
+static void ps2_handle_ack(struct ps2dev *ps2dev, u8 data)
 {
 	switch (data) {
 	case PS2_RET_ACK:
@@ -436,53 +520,25 @@ bool ps2_handle_ack(struct ps2dev *ps2dev, u8 data)
 		 */
 		dev_dbg(&ps2dev->serio->dev, "unexpected %#02x\n", data);
 		ps2dev->flags &= ~PS2_FLAG_WAITID;
-		return true;
+		return;
 	}
 
 	if (!ps2dev->nak)
 		ps2dev->flags &= ~PS2_FLAG_NAK;
 
 	ps2dev->flags &= ~PS2_FLAG_ACK;
-	wake_up(&ps2dev->wait);
 
 	if (!ps2dev->nak && data != PS2_RET_ACK)
 		ps2_handle_response(ps2dev, data);
-
-	return true;
-}
-EXPORT_SYMBOL(ps2_handle_ack);
-
-/*
- * ps2_handle_response() is supposed to be used in interrupt handler
- * to properly store device's response to a command and notify process
- * waiting for completion of the command.
- */
-
-bool ps2_handle_response(struct ps2dev *ps2dev, u8 data)
-{
-	if (ps2dev->cmdcnt)
-		ps2dev->cmdbuf[--ps2dev->cmdcnt] = data;
-
-	if (ps2dev->flags & PS2_FLAG_CMD1) {
-		ps2dev->flags &= ~PS2_FLAG_CMD1;
-		if (ps2dev->cmdcnt)
-			wake_up(&ps2dev->wait);
-	}
-
-	if (!ps2dev->cmdcnt) {
-		ps2dev->flags &= ~PS2_FLAG_CMD;
+	else
 		wake_up(&ps2dev->wait);
-	}
-
-	return true;
 }
-EXPORT_SYMBOL(ps2_handle_response);
 
 /*
  * Clears state of PS/2 device after communication error by resetting majority
  * of flags and waking up waiters, if any.
  */
-void ps2_cmd_aborted(struct ps2dev *ps2dev)
+static void ps2_cleanup(struct ps2dev *ps2dev)
 {
 	unsigned long old_flags = ps2dev->flags;
 
@@ -494,6 +550,46 @@ void ps2_cmd_aborted(struct ps2dev *ps2dev)
 
 	if (old_flags & (PS2_FLAG_ACK | PS2_FLAG_CMD))
 		wake_up(&ps2dev->wait);
+}
 
+/**
+ * ps2_interrupt - common interrupt handler for PS/2 devices
+ * @serio: serio port for the device
+ * @data: a data byte received from the device
+ * @flags: flags such as %SERIO_PARITY or %SERIO_TIMEOUT indicating state of
+ *   the data transfer
+ *
+ * ps2_interrupt() invokes pre-receive handler, optionally handles command
+ * acknowledgement and response from the device, and finally passes the data
+ * to the main protocol handler for future processing.
+ */
+irqreturn_t ps2_interrupt(struct serio *serio, u8 data, unsigned int flags) {
+	struct ps2dev *ps2dev = serio_get_drvdata(serio);
+	enum ps2_disposition rc;
+
+	rc = ps2dev->pre_receive_handler(ps2dev, data, flags);
+	switch (rc) {
+	case PS2_ERROR:
+		ps2_cleanup(ps2dev);
+		break;
+
+	case PS2_IGNORE:
+		break;
+
+	case PS2_PROCESS:
+		if (ps2dev->flags & PS2_FLAG_ACK)
+			ps2_handle_ack(ps2dev, data);
+		else if (ps2dev->flags & PS2_FLAG_CMD)
+			ps2_handle_response(ps2dev, data);
+		else
+			ps2dev->receive_handler(ps2dev, data);
+		break;
+	}
+
+	return IRQ_HANDLED;
 }
-EXPORT_SYMBOL(ps2_cmd_aborted);
+EXPORT_SYMBOL(ps2_interrupt);
+
+MODULE_AUTHOR("Dmitry Torokhov <dtor@mail.ru>");
+MODULE_DESCRIPTION("PS/2 driver library");
+MODULE_LICENSE("GPL");