linux-kernel - [PATCH v3 01/12] HID: ft260: ft260_xfer

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Message-Id: <20221030203403.4637-2-michael.zaidman@gmail.com>
Date:   Sun, 30 Oct 2022 22:33:52 +0200
From:   Michael Zaidman <michael.zaidman@...il.com>
To:     jikos@...nel.org
Cc:     linux-kernel@...r.kernel.org, linux-input@...r.kernel.org,
        linux-i2c@...r.kernel.org, germain.hebert@...abb.com,
        Enrik.Berkhan@...a.de, Michael Zaidman <michael.zaidman@...il.com>,
        Guillaume Champagne <champagne.guillaume.c@...il.com>
Subject: [PATCH v3 01/12] 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>
Tested-by: Guillaume Champagne <champagne.guillaume.c@...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);
-- 
2.34.1