From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.amicon.ru (mail.amicon.ru [77.108.111.100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3E7072FD1B3; Wed, 29 Apr 2026 13:53:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=77.108.111.100 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777470821; cv=none; b=PjpFRNilrR4fdCUGMsAH7HHLVlproY+OQse60eb4eYFdeme1QjrdG0PS9s3DmS0PgktY6ByBEY4ew92TXVmFYbdCieJKhbE7ahAmshvUv/beflGFBgUO3Nv+DII3dXEseOrQfSu7r7vKY+tYvVibvJBhTi0VSta7bLVBJ2CNU1I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1777470821; c=relaxed/simple; bh=FuV6t38owbOwUeQ5bl5rvJjuJFhjtOXS4dXpe55g2dc=; h=Content-Type:From:To:CC:Subject:Date:Message-ID:MIME-Version; b=hzIwfepIRKdyD2qjphUBjVGjreEAN5dPBgQ4KCmr0zu+/NXvA0eMydTvMxfrvQ3NiBqJm4eb2q5dV9DXGc/JD0JYZA7vB9BQmt9Mcy+lM+y2Mv0IKW3TAd/xAPB6tmCdFudZmQGhPlgkIJHvvM1NyowASpctyufptG7gwGhtAjM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amicon.ru; spf=pass smtp.mailfrom=amicon.ru; dkim=pass (2048-bit key) header.d=amicon.ru header.i=@amicon.ru header.b=S0Q+AYzH; arc=none smtp.client-ip=77.108.111.100 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amicon.ru Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amicon.ru Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=amicon.ru header.i=@amicon.ru header.b="S0Q+AYzH" Content-Transfer-Encoding: 8bit Content-Type: text/plain DKIM-Signature: v=1; a=rsa-sha256; d=amicon.ru; s=mail; c=simple/simple; t=1777469907; h=from:subject:to:date:message-id; bh=FuV6t38owbOwUeQ5bl5rvJjuJFhjtOXS4dXpe55g2dc=; b=S0Q+AYzHzvRlPeccqgK0RXwZagzRlkraVMomN+AaTBIiiiK4+DQ36xuOzsILyAh7kcugNzX65uO YQ+4JYUeWXtsfvidUTwr3fAXXPtTwoKNeODNY52StgJZrnqzRrRtZydh+g4HuLIg98G4HXUmRS8KW cKv194kAOMZrIUnDcLh6DiAZcNkNvNJO/nWaIdV6Rl997NpfThiNYDbIbDN9apFuSQkeI9fbnVOzH qwg4vfbnESy/FAXpIusAeu09Se1T1XZirVglKNNfOjtcbMV/g3ww6sBxbl7AhLCT11O/UQ1OvDAXS 164MhjxNdik3WjX+LQuSYyJ7GEstOh+V1oIw== Received: from example.com (172.16.2.46) by mail.amicon.lan (192.168.0.59) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.27; Wed, 29 Apr 2026 16:38:27 +0300 From: Agalakov Daniil To: Johan Hovold CC: Agalakov Daniil , Greg Kroah-Hartman , , , , Roman Razov , Iskhakov Daniil Subject: [PATCH] USB: serial: mos7720: fix actual baud rate not reported back to TTY Date: Wed, 29 Apr 2026 16:38:12 +0300 Message-ID: <20260429133815.317534-1-ade@amicon.ru> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-usb@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-ClientProxiedBy: mail.amicon.lan (192.168.0.59) To mail.amicon.lan (192.168.0.59) The calc_baud_rate_divisor() function computes a divisor from the requested baud rate using integer arithmetic, which means the actual hardware baud rate may differ from the requested one. Previously this rounded value was never propagated back to the TTY layer, so tty_encode_baud_rate() was called with the requested rate rather than the actual one. Change baudrate parameters in calc_baud_rate_divisor() and send_cmd_write_baud_rate() to pointers so the actual resulting baud rate can be written back to the caller. Update *baudrate with the computed value (230400 / custom) after divisor calculation. In change_port_settings(), pass &baud to send_cmd_write_baud_rate() and guard tty_encode_baud_rate() with a status check, so the TTY is only updated on success and receives the true hardware baud rate. Found by Linux Verification Center (linuxtesting.org) with SVACE. Fixes: 65d063ab21fe ("USB: mos7720: clean up termios") Co-developed-by: Iskhakov Daniil Signed-off-by: Iskhakov Daniil Signed-off-by: Agalakov Daniil --- drivers/usb/serial/mos7720.c | 29 ++++++++++++++--------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/drivers/usb/serial/mos7720.c b/drivers/usb/serial/mos7720.c index 94459408e7fb..1052217edf26 100644 --- a/drivers/usb/serial/mos7720.c +++ b/drivers/usb/serial/mos7720.c @@ -1264,9 +1264,9 @@ static const struct divisor_table_entry divisor_table[] = { /***************************************************************************** * calc_baud_rate_divisor * this function calculates the proper baud rate divisor for the specified - * baud rate. + * baud rate and updates the baudrate parameter with the actual value. *****************************************************************************/ -static int calc_baud_rate_divisor(struct usb_serial_port *port, int baudrate, int *divisor) +static int calc_baud_rate_divisor(struct usb_serial_port *port, int *baudrate, int *divisor) { int i; __u16 custom; @@ -1274,10 +1274,10 @@ static int calc_baud_rate_divisor(struct usb_serial_port *port, int baudrate, in __u16 round; - dev_dbg(&port->dev, "%s - %d\n", __func__, baudrate); + dev_dbg(&port->dev, "%s - %d\n", __func__, *baudrate); for (i = 0; i < ARRAY_SIZE(divisor_table); i++) { - if (divisor_table[i].baudrate == baudrate) { + if (divisor_table[i].baudrate == *baudrate) { *divisor = divisor_table[i].divisor; return 0; } @@ -1285,18 +1285,19 @@ static int calc_baud_rate_divisor(struct usb_serial_port *port, int baudrate, in /* After trying for all the standard baud rates * * Try calculating the divisor for this baud rate */ - if (baudrate > 75 && baudrate < 230400) { + if (*baudrate > 75 && *baudrate < 230400) { /* get the divisor */ - custom = (__u16)(230400L / baudrate); + custom = (__u16)(230400L / *baudrate); /* Check for round off */ - round1 = (__u16)(2304000L / baudrate); + round1 = (__u16)(2304000L / *baudrate); round = (__u16)(round1 - (custom * 10)); if (round > 4) custom++; *divisor = custom; + *baudrate = 230400L / custom; - dev_dbg(&port->dev, "Baud %d = %d\n", baudrate, custom); + dev_dbg(&port->dev, "Baud %d = %d\n", *baudrate, custom); return 0; } @@ -1307,10 +1308,10 @@ static int calc_baud_rate_divisor(struct usb_serial_port *port, int baudrate, in /* * send_cmd_write_baud_rate * this function sends the proper command to change the baud rate of the - * specified port. + * specified port and updates the baudrate parameter with the actual value. */ static int send_cmd_write_baud_rate(struct moschip_port *mos7720_port, - int baudrate) + int *baudrate) { struct usb_serial_port *port; struct usb_serial *serial; @@ -1325,7 +1326,7 @@ static int send_cmd_write_baud_rate(struct moschip_port *mos7720_port, serial = port->serial; number = port->port_number; - dev_dbg(&port->dev, "%s - baud = %d\n", __func__, baudrate); + dev_dbg(&port->dev, "%s - baud = %d\n", __func__, *baudrate); /* Calculate the Divisor */ status = calc_baud_rate_divisor(port, baudrate, &divisor); @@ -1474,10 +1475,8 @@ static void change_port_settings(struct tty_struct *tty, } dev_dbg(&port->dev, "%s - baud rate = %d\n", __func__, baud); - status = send_cmd_write_baud_rate(mos7720_port, baud); - /* FIXME: needs to write actual resulting baud back not just - blindly do so */ - if (cflag & CBAUD) + status = send_cmd_write_baud_rate(mos7720_port, &baud); + if (!status && (cflag & CBAUD)) tty_encode_baud_rate(tty, baud, baud); /* Enable Interrupts */ write_mos_reg(serial, port_number, MOS7720_IER, 0x0c); -- 2.51.0