linux-kernel - [PATCH v1 1/5] HID: ft260: ft260_xfer

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Message-Id: <20220525074757.7519-2-michael.zaidman@gmail.com>
Date:   Wed, 25 May 2022 10:47:53 +0300
From:   Michael Zaidman <michael.zaidman@...il.com>
To:     jikos@...nel.org, benjamin.tissoires@...hat.com, wsa@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        linux-i2c@...r.kernel.org, champagne.guillaume.c@...il.com,
        mathieu.gallichand@...atest.com,
        Michael Zaidman <michael.zaidman@...il.com>
Subject: [PATCH v1 1/5] HID: ft260: ft260_xfer_status routine cleanup

After clarifying with FTDI's support, it turned out that the error condition
(bit 1) in byte 1 of the i2c status HID report is a status bit reflecting all
error conditions. When bits 2, 3, or 4 are raised to 1, bit 1 is set to 1 also.
Since the ft260_xfer_status routine tests the error condition bit and exits
in the case of an error, the program flow never reaches the conditional
expressions for 2, 3, and 4 bits when any of them indicates an error state.
Though these expressions are never evaluated to true, they are checked several
times per IO, increasing the ft260_xfer_status polling cycle duration.

The patch removes the conditional expressions for 2, 3, and 4 bits in byte 1
of the i2c status HID report.

Signed-off-by: Michael Zaidman <michael.zaidman@...il.com>
---
 drivers/hid/hid-ft260.c | 30 ++++++++++--------------------
 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c
index 79505c64dbfe..a35201d68b15 100644
--- a/drivers/hid/hid-ft260.c
+++ b/drivers/hid/hid-ft260.c
@@ -313,27 +313,17 @@ static int ft260_xfer_status(struct ft260_device *dev)
 	if (report.bus_status & FT260_I2C_STATUS_CTRL_BUSY)
 		return -EAGAIN;
 
-	if (report.bus_status & FT260_I2C_STATUS_BUS_BUSY)
-		return -EBUSY;
-
-	if (report.bus_status & FT260_I2C_STATUS_ERROR)
+	/*
+	 * The error condition (bit 1) is a status bit reflecting any
+	 * error conditions. When any of the bits 2, 3, or 4 are raised
+	 * to 1, bit 1 is also set to 1.
+	 */
+	if (report.bus_status & FT260_I2C_STATUS_ERROR) {
+		hid_err(hdev, "i2c bus error: %#02x\n", report.bus_status);
 		return -EIO;
+	}
 
-	ret = -EIO;
-
-	if (report.bus_status & FT260_I2C_STATUS_ADDR_NO_ACK)
-		ft260_dbg("unacknowledged address\n");
-
-	if (report.bus_status & FT260_I2C_STATUS_DATA_NO_ACK)
-		ft260_dbg("unacknowledged data\n");
-
-	if (report.bus_status & FT260_I2C_STATUS_ARBITR_LOST)
-		ft260_dbg("arbitration loss\n");
-
-	if (report.bus_status & FT260_I2C_STATUS_CTRL_IDLE)
-		ret = 0;
-
-	return ret;
+	return 0;
 }
 
 static int ft260_hid_output_report(struct hid_device *hdev, u8 *data,
@@ -376,7 +366,7 @@ static int ft260_hid_output_report_check_status(struct ft260_device *dev,
 			break;
 	} while (--try);
 
-	if (ret == 0 || ret == -EBUSY)
+	if (ret == 0)
 		return 0;
 
 	ft260_i2c_reset(hdev);
-- 
2.25.1