[PATCH v2 4/7] Input: synaptics-rmi4 - f55: handle zero electrode count

[Caleb Connolly <caleb.connolly@linaro.org>]

From: methanal <baclofen@tuta.io>

Some third party ICs claim to support f55 but report an electrode count
of 0. Catch this and bail out early so that we don't confuse the i2c bus
with 0 sized reads.

Signed-off-by: methanal <baclofen@tuta.io>
[simplify code, adjust wording]
Signed-off-by: Caleb Connolly <caleb.connolly@linaro.org>
---
 drivers/input/rmi4/rmi_f55.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/input/rmi4/rmi_f55.c b/drivers/input/rmi4/rmi_f55.c
index 488adaca4dd0..ad2ef14ae9f4 100644
--- a/drivers/input/rmi4/rmi_f55.c
+++ b/drivers/input/rmi4/rmi_f55.c
@@ -52,6 +52,11 @@ static int rmi_f55_detect(struct rmi_function *fn)
 
 	f55->num_rx_electrodes = f55->qry[F55_NUM_RX_OFFSET];
 	f55->num_tx_electrodes = f55->qry[F55_NUM_TX_OFFSET];
+	if (!f55->num_rx_electrodes || !f55->num_tx_electrodes) {
+		rmi_dbg(RMI_DEBUG_FN, &fn->dev,
+			"F55 query returned no electrodes, giving up\n");
+		return 0;
+	}
 
 	f55->cfg_num_rx_electrodes = f55->num_rx_electrodes;
 	f55->cfg_num_tx_electrodes = f55->num_rx_electrodes;

-- 
2.42.0