[PATCH] HID: i2c-hid: Add quirk for sleep before reset

[Brendan McGrath]

Support for the Asus Touchpad was recently added. It turns out this
device can fail initialisation (and become unusable) when the RESET
command is sent too soon after the POWER ON command.

Unfortunately the i2c-hid specification does not specify the need for
a delay between these two commands. But it was discovered the Windows
driver has a 1ms delay.

As a result, this patch adds a new QUIRK to the i2c-hid module that
allows a device to specify a specific sleep inbetween the POWER ON and
RESET commands.

See https://github.com/vlasenko/hid-asus-dkms/issues/24 for further
details.

Signed-off-by: Brendan McGrath <redmcg@xxxxxxxxxxxxxxxxxxx>
---
I considered three approaches for this patch:
a) add a hardcoded sleep that would affect all devices;
b) add a quirk with a hardcoded sleep value; or
c) add a quirk with a configurable sleep value

Each was a trade off between flexibility and the amount of code/complexity required.

In the end I chose c) as this allowed for the most flexibility; but would
be happy to resubmit the patch using one of the other options (or any other
alternative).

 drivers/hid/i2c-hid/i2c-hid.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/drivers/hid/i2c-hid/i2c-hid.c b/drivers/hid/i2c-hid/i2c-hid.c
index 8d53efe..fb1ebfa 100644
--- a/drivers/hid/i2c-hid/i2c-hid.c
+++ b/drivers/hid/i2c-hid/i2c-hid.c
@@ -45,6 +45,7 @@
 
 /* quirks to control the device */
 #define I2C_HID_QUIRK_SET_PWR_WAKEUP_DEV	BIT(0)
+#define I2C_HID_QUIRK_SLEEP_BEFORE_RESET	BIT(1)
 
 /* flags */
 #define I2C_HID_STARTED		0
@@ -156,17 +157,26 @@ struct i2c_hid {
 
 	bool			irq_wake_enabled;
 	struct mutex		reset_lock;
+
+	__u32			reset_usleep_low;
+	__u32			reset_usleep_high;
 };
 
 static const struct i2c_hid_quirks {
 	__u16 idVendor;
 	__u16 idProduct;
 	__u32 quirks;
+	__u32 reset_usleep_low;
+	__u32 reset_usleep_high;
 } i2c_hid_quirks[] = {
 	{ USB_VENDOR_ID_WEIDA, USB_DEVICE_ID_WEIDA_8752,
 		I2C_HID_QUIRK_SET_PWR_WAKEUP_DEV },
 	{ USB_VENDOR_ID_WEIDA, USB_DEVICE_ID_WEIDA_8755,
 		I2C_HID_QUIRK_SET_PWR_WAKEUP_DEV },
+	{ USB_VENDOR_ID_ASUSTEK, USB_DEVICE_ID_ASUSTEK_TOUCHPAD,
+		I2C_HID_QUIRK_SLEEP_BEFORE_RESET,
+		 .reset_usleep_low = 750,
+		 .reset_usleep_high = 5000 },
 	{ 0, 0 }
 };
 
@@ -177,16 +187,16 @@ static const struct i2c_hid_quirks {
  *
  * Returns: a u32 quirks value.
  */
-static u32 i2c_hid_lookup_quirk(const u16 idVendor, const u16 idProduct)
+static const struct i2c_hid_quirks* i2c_hid_lookup_quirk(const u16 idVendor, const u16 idProduct)
 {
-	u32 quirks = 0;
+	const struct i2c_hid_quirks *quirks = NULL;
 	int n;
 
 	for (n = 0; i2c_hid_quirks[n].idVendor; n++)
 		if (i2c_hid_quirks[n].idVendor == idVendor &&
 		    (i2c_hid_quirks[n].idProduct == (__u16)HID_ANY_ID ||
 		     i2c_hid_quirks[n].idProduct == idProduct))
-			quirks = i2c_hid_quirks[n].quirks;
+			quirks = &i2c_hid_quirks[n];
 
 	return quirks;
 }
@@ -425,6 +435,9 @@ static int i2c_hid_hwreset(struct i2c_client *client)
 	if (ret)
 		goto out_unlock;
 
+	if (ihid->quirks & I2C_HID_QUIRK_SLEEP_BEFORE_RESET)
+		usleep_range(ihid->reset_usleep_low, ihid->reset_usleep_high);
+
 	i2c_hid_dbg(ihid, "resetting...\n");
 
 	ret = i2c_hid_command(client, &hid_reset_cmd, NULL, 0);
@@ -1005,6 +1018,7 @@ static int i2c_hid_probe(struct i2c_client *client,
 	struct i2c_hid *ihid;
 	struct hid_device *hid;
 	__u16 hidRegister;
+	const struct i2c_hid_quirks *quirks;
 	struct i2c_hid_platform_data *platform_data = client->dev.platform_data;
 
 	dbg_hid("HID probe called for i2c 0x%02x\n", client->addr);
@@ -1091,7 +1105,15 @@ static int i2c_hid_probe(struct i2c_client *client,
 		 client->name, hid->vendor, hid->product);
 	strlcpy(hid->phys, dev_name(&client->dev), sizeof(hid->phys));
 
-	ihid->quirks = i2c_hid_lookup_quirk(hid->vendor, hid->product);
+	quirks = i2c_hid_lookup_quirk(hid->vendor, hid->product);
+
+	if (quirks)
+		ihid->quirks = quirks->quirks;
+
+	if (ihid->quirks & I2C_HID_QUIRK_SLEEP_BEFORE_RESET) {
+		ihid->reset_usleep_low = quirks->reset_usleep_low;
+		ihid->reset_usleep_high = quirks->reset_usleep_high;
+	}
 
 	ret = hid_add_device(hid);
 	if (ret) {
-- 
2.7.4