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([37.142.145.227]) by smtp.googlemail.com with ESMTPSA id ffacd0b85a97d-48e71b959c1sm5457300f8f.45.2026.10.30.15.37.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 30 Oct 2026 15:37:24 -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 13/15] HID: ft260: i2c: reject an I2C clock outside the supported range Date: Sat, 31 Oct 2026 00:36:35 +0200 Message-ID: <20261030223637.86907-14-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-i2c@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 The clock sysfs attribute passes any 16-bit value to the chip. The chip accepts it, reports it back in the I2C status report that clock_show reads, and runs the bus at the 100 kHz default. A read of 2048 bytes takes the same 0.298 s after writing 50, 3500 or 65535 as it does after writing 100, while 60 and 3400 give 0.387 s and 0.058 s. Userspace has no way to see that the value was not applied. Refuse a value outside the 60-3400 kHz range named in the datasheet section 4.4.16. ft260_uart_change_speed() checks the baud rate against FT260_UART_CFG_BAUD_MIN and FT260_UART_CFG_BAUD_MAX, but termios has no error return, so it falls back to 9600. A sysfs store can return an error, so the clock store refuses the value. FT260_WORD_ATTR_STORE() takes the parse function as a parameter now, so a word attribute with no range of its own keeps passing kstrtou16. Signed-off-by: Michael Zaidman --- drivers/hid/hid-ft260.c | 31 ++++++++++++++++++++++++++++--- 1 file changed, 28 insertions(+), 3 deletions(-) diff --git a/drivers/hid/hid-ft260.c b/drivers/hid/hid-ft260.c index 50f68790c04d..f7d01d9e07f7 100644 --- a/drivers/hid/hid-ft260.c +++ b/drivers/hid/hid-ft260.c @@ -68,6 +68,11 @@ MODULE_PARM_DESC(debug, "Toggle FT260 debugging messages"); #define FT260_WR_I2C_DATA_MAX 60 #define FT260_WR_UART_DATA_MAX 62 + +/* I2C bus clock range in kHz, see the FT260 datasheet section 4.4.16 */ +#define FT260_I2C_CLOCK_MIN 60 +#define FT260_I2C_CLOCK_MAX 3400 + #define FT260_GPIOCHIP "ft260_gpio" #define FT260_GPIO_0_5_COUNT 6 #define FT260_GPIO_A_H_COUNT 8 @@ -1529,6 +1534,25 @@ static void ft260_attr_dummy_func(struct hid_device *hdev, u8 req, u16 value) { } +/* + * The chip takes any 16-bit value and reports it back in the I2C status + * report, but runs the bus at the 100 kHz default when the value is + * outside the documented range. The report gives no way to tell the two + * cases apart, so refuse the value here. + */ +static int ft260_i2c_clock_parse(const char *buf, unsigned int base, u16 *clock) +{ + int ret = kstrtou16(buf, base, clock); + + if (ret) + return ret; + + if (*clock < FT260_I2C_CLOCK_MIN || *clock > FT260_I2C_CLOCK_MAX) + return -EINVAL; + + return 0; +} + #define FT260_ATTR_SHOW(name, reptype, id, type, func) \ static ssize_t name##_show(struct device *kdev, \ struct device_attribute *attr, char *buf) \ @@ -1586,9 +1610,9 @@ static void ft260_attr_dummy_func(struct hid_device *hdev, u8 req, u16 value) FT260_ATTR_STORE(name, reptype, FT260_SYSTEM_SETTINGS, req, \ u8, kstrtou8, func, FT260_STORE_NATIVE) -#define FT260_WORD_ATTR_STORE(name, reptype, req, func) \ +#define FT260_WORD_ATTR_STORE(name, reptype, req, strtou, func) \ FT260_ATTR_STORE(name, reptype, FT260_SYSTEM_SETTINGS, req, \ - u16, kstrtou16, func, cpu_to_le16) + u16, strtou, func, cpu_to_le16) FT260_SSTAT_ATTR_SHOW(chip_mode); static DEVICE_ATTR_RO(chip_mode); @@ -1641,7 +1665,8 @@ static DEVICE_ATTR_RW(clock_ctl); FT260_I2CST_ATTR_SHOW(clock); FT260_WORD_ATTR_STORE(clock, ft260_set_i2c_speed_report, - FT260_SET_I2C_CLOCK_SPEED, ft260_attr_dummy_func); + FT260_SET_I2C_CLOCK_SPEED, ft260_i2c_clock_parse, + ft260_attr_dummy_func); static DEVICE_ATTR_RW(clock); static ssize_t i2c_reset_store(struct device *kdev, -- 2.43.0