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([37.142.145.227]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-48e71b959c1sm5457300f8f.45.2026.10.30.15.37.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Oct 2026 15:37:26 -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 Subject: [PATCH v2 14/15] HID: ft260: i2c: fix i2c_reset sysfs store return value Date: Sat, 31 Oct 2026 00:36:36 +0200 Message-ID: <20261030223637.86907-15-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 A sysfs store must return the number of bytes it consumed. kernfs hands that value straight to write(2). i2c_reset_store() returns whatever ft260_i2c_reset() returns, which is the length of the feature report it sent, 2, not 0. The "return count" below it never runs, so every write to i2c_reset returns 2 whatever its size. A write of two bytes is right by coincidence, because the report is two bytes long. A caller that leaves out the newline, as C and Python code usually does, writes one byte and gets 2 back, which is more than it asked for: echo -n 1 > i2c_reset 1 byte, write() returns 2, bash ignores it printf 1 > i2c_reset 1 byte, dash reports an I/O error echo 1 > i2c_reset 2 bytes, correct by coincidence Return 0 from ft260_i2c_reset() on success. The value is discarded by its other callers, ft260_hid_output_report_check_status(), ft260_i2c_probe() and ft260_i2c_abort(), whose own four callers discard it as well. Fixes: 6a82582d9fa4 ("HID: ft260: add usb hid to i2c host bridge driver") Signed-off-by: Michael Zaidman --- drivers/hid/hid-ft260.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c index f7d01d9e07f7..cd1117c170e1 100644 --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -551,7 +551,7 @@ static int ft260_i2c_reset(struct hid_device *hdev) } ft260_dbg("done\n"); - return ret; + return 0; } static int ft260_hid_output_report(struct hid_device *hdev, u8 *data, -- 2.43.0