From: Andrew Duggan <aduggan@synaptics.com>
To: linux-input@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Andrew Duggan <aduggan@synaptics.com>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        Benjamin Tissoires <benjamin.tissoires@redhat.com>,
        Nick Dyer <nick@shmanahar.org>, Jiri Kosina <jikos@kernel.org>
Subject: [PATCH] Input: synaptics-rmi4 - Only read the F54 query registers which are used
Date: Tue, 20 Jun 2017 16:08:48 -0700
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The F54 driver is currently only using the first 6 bytes of F54 so there
is no need to read all 27 bytes. Some Dell systems
(Dell XP13 9333 and similar) have an issue with the touchpad or I2C bus
when readiing reports larger then 16 bytes. Reads larger then 16 bytes
are reported in two HID reports. Something about the back to back
reports seems to cause the next read to report incorrect data. This
results in F30 failing to load and the click button failing to work.

Previous issues with the I2C controller or touchpad were addressed in:
commit 5b65c2a02966 ("HID: rmi: check sanity of the incoming report")

Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=195949
Signed-off-by: Andrew Duggan <aduggan@synaptics.com>
---
Also, in addition to changing the size of the read I moved the query
buffer. I figured that since the query buffer is only acceessed in the
rmi_f54_detect function it was not necessary keep it in f54_data. The
parsed values are already being stored in f54_data.

Thanks,
Andrew


 drivers/input/rmi4/rmi_f54.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/input/rmi4/rmi_f54.c b/drivers/input/rmi4/rmi_f54.c
index dea63e2..f5206e2 100644
--- a/drivers/input/rmi4/rmi_f54.c
+++ b/drivers/input/rmi4/rmi_f54.c
@@ -31,9 +31,6 @@
 #define F54_GET_REPORT          1
 #define F54_FORCE_CAL           2
 
-/* Fixed sizes of reports */
-#define F54_QUERY_LEN			27
-
 /* F54 capabilities */
 #define F54_CAP_BASELINE	(1 << 2)
 #define F54_CAP_IMAGE8		(1 << 3)
@@ -95,7 +92,6 @@ struct rmi_f54_reports {
 struct f54_data {
 	struct rmi_function *fn;
 
-	u8 qry[F54_QUERY_LEN];
 	u8 num_rx_electrodes;
 	u8 num_tx_electrodes;
 	u8 capabilities;
@@ -632,22 +628,23 @@ static int rmi_f54_detect(struct rmi_function *fn)
 {
 	int error;
 	struct f54_data *f54;
+	u8 buf[6];
 
 	f54 = dev_get_drvdata(&fn->dev);
 
 	error = rmi_read_block(fn->rmi_dev, fn->fd.query_base_addr,
-			       &f54->qry, sizeof(f54->qry));
+			       buf, sizeof(buf));
 	if (error) {
 		dev_err(&fn->dev, "%s: Failed to query F54 properties\n",
 			__func__);
 		return error;
 	}
 
-	f54->num_rx_electrodes = f54->qry[0];
-	f54->num_tx_electrodes = f54->qry[1];
-	f54->capabilities = f54->qry[2];
-	f54->clock_rate = f54->qry[3] | (f54->qry[4] << 8);
-	f54->family = f54->qry[5];
+	f54->num_rx_electrodes = buf[0];
+	f54->num_tx_electrodes = buf[1];
+	f54->capabilities = buf[2];
+	f54->clock_rate = buf[3] | (buf[4] << 8);
+	f54->family = buf[5];
 
 	rmi_dbg(RMI_DEBUG_FN, &fn->dev, "F54 num_rx_electrodes: %d\n",
 		f54->num_rx_electrodes);
-- 
2.7.4