[PATCH v10 fixup 1/2] mfd: asus-transformer-ec: use 8-byte event reads on SL101

[Florian Krischer <florian.krischer@fkr.dev>]

The SL101 embedded controller exposes the event window at 0x6a through
8-byte reads. This matches the downstream ASUS SL101 driver, which uses
an 8-byte SMBus I2C block read for command responses and events.

The generic 32-byte event read used by v10 prevents the physical SL101
keyboard from completing PS/2 initialization.

Use a variant-specific event read length for the SL101 in both the
clear-buffer and interrupt paths. Keep the 32-byte entry size for other
variants.

Tested on an ASUS Eee Pad Slider SL101 with EC firmware SL101-0202.
With the matching serio fixup, the built-in keyboard completes atkbd
initialization and works.

Signed-off-by: Florian Krischer <florian.krischer@fkr.dev>
---
 drivers/mfd/asus-transformer-ec.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

--- a/drivers/mfd/asus-transformer-ec.c
+++ b/drivers/mfd/asus-transformer-ec.c
@@ -229,8 +229,18 @@
 	return ret;
 }

+static size_t asus_ec_read_size(const struct asus_ec_data *ddata)
+{
+	/* SL101 firmware exposes an 8-byte event window at 0x6a. */
+	if (ddata->info->variant == ASUSEC_SL101_DOCK)
+		return 8;
+
+	return ASUSEC_ENTRY_SIZE;
+}
+
 static void asus_ec_clear_buffer(struct asus_ec_data *ddata)
 {
+	size_t read_size = asus_ec_read_size(ddata);
 	int ret, retry = ASUSEC_RSP_BUFFER_SIZE;

 	/*
@@ -239,8 +249,8 @@
 	 */
 	while (retry--) {
 		ret = i2c_smbus_read_i2c_block_data(ddata->client, ASUSEC_READ_BUF,
-						    ASUSEC_ENTRY_SIZE, ddata->ec_buf);
-		if (ret < ASUSEC_ENTRY_SIZE)
+						    read_size, ddata->ec_buf);
+		if (ret < read_size)
 			continue;

 		if (ddata->ec_buf[ASUSEC_IRQ_STATUS] & ASUSEC_OBF_MASK)
@@ -318,12 +328,13 @@
 static irqreturn_t asus_ec_interrupt(int irq, void *dev_id)
 {
 	struct asus_ec_data *ddata = dev_id;
+	size_t read_size = asus_ec_read_size(ddata);
 	unsigned long notify_action;
 	int ret;

 	ret = i2c_smbus_read_i2c_block_data(ddata->client, ASUSEC_READ_BUF,
-					    ASUSEC_ENTRY_SIZE, ddata->ec_buf);
-	if (ret < ASUSEC_ENTRY_SIZE)
+					    read_size, ddata->ec_buf);
+	if (ret < read_size)
 		return IRQ_NONE;

 	/* Check status byte with ASUSEC_OBF_MASK if data is valid */
--