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([37.142.145.227]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-48e71b959c1sm5457300f8f.45.2026.10.30.15.37.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Oct 2026 15:37:18 -0700 (PDT) From: Michael Zaidman To: Jiri Kosina , Benjamin Tissoires Cc: Linus Walleij , Bartosz Golaszewski , Greg Kroah-Hartman , Jiri Slaby , Raman Varabets , Germain Hebert , Christina Quast , Rio Liu , Bruno Giacomazzi , linux-input@vger.kernel.org, linux-serial@vger.kernel.org, linux-gpio@vger.kernel.org, linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Michael Zaidman , Chris Keeser Subject: [PATCH v2 10/15] HID: ft260: i2c: fix large write transaction failure Date: Sat, 31 Oct 2026 00:36:32 +0200 Message-ID: <20261030223637.86907-11-michael.zaidman@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261030223637.86907-1-michael.zaidman@gmail.com> References: <20261030223637.86907-1-michael.zaidman@gmail.com> X-Mailing-List: linux-serial@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Fixes a regression from commit 5afac727defa ("HID: ft260: missed NACK from busy device"), which waited for bus-idle after every HID write report except when the report flag was exactly FT260_FLAG_START. Multi-report I2C writes keep the bus busy between chunks for atomicity. Treating those middle reports like a final STOP caused ft260_xfer_status() to spin on -EAGAIN after the second HID report and fail large writes. Write-then-read combined transfers still worked. Pass the bus-busy check policy from the caller: ft260_i2c_write() and ft260_smbus_write() wait for idle only when the report they send carries STOP; intermediate chunks and the command phase of a combined transfer do not. The SMBus side matters for register reads. The command phase is written with FT260_FLAG_START and no STOP, because a repeated START read follows and the controller deliberately keeps the bus busy to keep the transaction atomic. Checking the busy bit there makes ft260_xfer_status() return -EAGAIN on every retry and the command write fail with -EIO, which breaks probing of clients that read registers: ads1x19 6-0040: Failed to read config register: -5 leds-pca963x: probe of 6-0008 failed with error -5 Fixes: 5afac727defa ("HID: ft260: missed NACK from busy device") Reported-by: Chris Keeser Closes: https://github.com/MichaelZaidman/hid-ft260/issues/35 Tested-by: Chris Keeser Reported-by: Bruno Giacomazzi Closes: https://github.com/MichaelZaidman/hid-ft260/issues/42 Signed-off-by: Michael Zaidman --- drivers/hid/hid-ft260.c | 35 ++++++++++++++++------------------- 1 file changed, 16 insertions(+), 19 deletions(-) diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c index dca0250f2c25..65835e13fa2a 100644 --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -576,9 +576,14 @@ static int ft260_xfer_status(struct ft260_device *dev, u8 bus_busy) } dev->clock = le16_to_cpu(report.clock); - ft260_dbg("bus_status %#02x, clock %u\n", report.bus_status, - dev->clock); + ft260_dbg("bus_status %#02x, clock %u, bus_busy %#02x\n", + report.bus_status, dev->clock, bus_busy); + /* + * Do not check the busy bit for combined transactions + * since the controller keeps the bus busy between writing + * and reading IOs to ensure an atomic operation. + */ if (report.bus_status & (FT260_I2C_STATUS_CTRL_BUSY | bus_busy)) return -EAGAIN; @@ -612,13 +617,10 @@ static int ft260_hid_output_report(struct hid_device *hdev, u8 *data, } static int ft260_hid_output_report_check_status(struct ft260_device *dev, - u8 *data, int len) + u8 *data, int len, u8 bus_busy) { - u8 bus_busy; int ret, usec, try = 100; struct hid_device *hdev = dev->hdev; - struct ft260_i2c_write_request_report *rep = - (struct ft260_i2c_write_request_report *)data; ret = ft260_hid_output_report(hdev, data, len); if (ret < 0) { @@ -635,16 +637,6 @@ static int ft260_hid_output_report_check_status(struct ft260_device *dev, ft260_dbg("wait %d usec, len %d\n", usec, len); } - /* - * Do not check the busy bit for combined transactions - * since the controller keeps the bus busy between writing - * and reading IOs to ensure an atomic operation. - */ - if (rep->flag == FT260_FLAG_START) - bus_busy = 0; - else - bus_busy = FT260_I2C_STATUS_BUS_BUSY; - do { ret = ft260_xfer_status(dev, bus_busy); if (ret != -EAGAIN) @@ -661,6 +653,7 @@ static int ft260_hid_output_report_check_status(struct ft260_device *dev, static int ft260_i2c_write(struct ft260_device *dev, u8 addr, u8 *data, int len, u8 flag) { + u8 bus_busy = 0; int ret, wr_len, idx = 0; struct ft260_i2c_write_request_report *rep = (struct ft260_i2c_write_request_report *)dev->i2c_wr_buf; @@ -673,8 +666,10 @@ static int ft260_i2c_write(struct ft260_device *dev, u8 addr, u8 *data, do { if (len <= FT260_WR_I2C_DATA_MAX) { wr_len = len; - if (flag == FT260_FLAG_START_STOP) + if (flag == FT260_FLAG_START_STOP) { rep->flag |= FT260_FLAG_STOP; + bus_busy = FT260_I2C_STATUS_BUS_BUSY; + } } else { wr_len = FT260_WR_I2C_DATA_MAX; } @@ -690,7 +685,7 @@ static int ft260_i2c_write(struct ft260_device *dev, u8 addr, u8 *data, rep->flag, data[0]); ret = ft260_hid_output_report_check_status(dev, (u8 *)rep, - wr_len + 4); + wr_len + 4, bus_busy); if (ret < 0) { ft260_dbg("failed with %d\n", ret); return ret; @@ -731,7 +726,9 @@ static int ft260_smbus_write(struct ft260_device *dev, u8 addr, u8 cmd, ft260_dbg("rep %#02x addr %#02x cmd %#02x datlen %d replen %d\n", rep->report, addr, cmd, rep->length, len); - ret = ft260_hid_output_report_check_status(dev, (u8 *)rep, len); + ret = ft260_hid_output_report_check_status(dev, (u8 *)rep, len, + (flag & FT260_FLAG_STOP) ? + FT260_I2C_STATUS_BUS_BUSY : 0); if (ret < 0) ft260_dbg("failed with %d\n", ret); -- 2.43.0