[PATCH v3 01/12] HID: ft260: ft260_xfer_status routine cleanup

Michael Zaidman
2022-10-30T20:34:27Z

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@gmail.com>
Tested-by: Guillaume Champagne <champagne.guillaume.c@gmail.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