From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC5A5CCA47C for ; Sun, 24 Jul 2022 12:20:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232624AbiGXMUx (ORCPT ); Sun, 24 Jul 2022 08:20:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39000 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229450AbiGXMUw (ORCPT ); Sun, 24 Jul 2022 08:20:52 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B1702D92 for ; Sun, 24 Jul 2022 05:20:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4CC6E61049 for ; Sun, 24 Jul 2022 12:20:51 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id ACBA8C3411E; Sun, 24 Jul 2022 12:20:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658665250; bh=9oa6ZKzUpEHAYnP8Kd9PAuB8Sy4kuuavFNYHYwcGb5o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=RpSw35D7JmJPcJkmumX5U3Pi/iRbtNdf7RgpzieYwsoqCxDqj8r9Op+N+YP5JdyLx s1oJLirfAX3WzpGmKqqA1I/+RhTpe5eClex9cuSalJPnsRa5gWwBVCmgYahvVYXUdC xLWYsdJnMPFRCGercAELfpGkDsExhFO95i6gSEpsh9xJ5obpRJ4y01W5Z+pvbrfjrx SioNA8wt/Oh1B8WMcx67mFDfgosuevP7CbqXrkMrE3ptqUeoYj4nGd+BhQ5eCS7OxQ rmiqf6ojF4c7dSwh4ehF3szQ4xg9wfX9QzPlbmXABn3FFqSpeSsq7Bc4dkqyVL/NiE 8dfc5buW+DeoA== Received: from johan by xi.lan with local (Exim 4.94.2) (envelope-from ) id 1oFabS-0006Xq-Jm; Sun, 24 Jul 2022 14:20:59 +0200 Date: Sun, 24 Jul 2022 14:20:58 +0200 From: Johan Hovold To: Marek =?utf-8?B?QmVow7pu?= Cc: linux-usb@vger.kernel.org, Pali =?utf-8?B?Um9ow6Fy?= , Greg Kroah-Hartman Subject: Re: [PATCH v2 4/7] USB: serial: ftdi_sio: Do not reset baud rate to 9600 Baud on error Message-ID: References: <20220712115306.26471-1-kabel@kernel.org> <20220712115306.26471-5-kabel@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20220712115306.26471-5-kabel@kernel.org> Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org On Tue, Jul 12, 2022 at 01:53:03PM +0200, Marek Behún wrote: > From: Pali Rohár > > If setting new baud rate fails, all other drivers leave the device at > previous baud rate, only ftdi_sio resets to 9600 Baud. > Change this behavior to that of other drivers so that /dev/ttyUSB* > devices behave in the same way. These statements are not true. Several USB serial driver set 9600 baud on errors for historical reasons. Yet others clamp. It's inconsistent at best. > Signed-off-by: Pali Rohár > Tested-by: Marek Behún > Signed-off-by: Marek Behún > --- > Greg pointed out that this make break some people's workflow, that they > may depend on this behavior. > > This is of course possible, although IMO improbable: it would be weird > to depend on the fall back to 9600 Baud on error, instead of expecting > that the baud rate didn't change at all (like in other /dev/ttyUSB* > drivers). > > Nonetheless if someone complains that they workflow got broken, we will > need to revert this. > static u32 get_ftdi_divisor(struct tty_struct *tty, > - struct usb_serial_port *port) > + struct usb_serial_port *port, speed_t old_baud) > { > struct ftdi_private *priv = usb_get_serial_port_data(port); > struct device *dev = &port->dev; > @@ -1322,6 +1322,8 @@ static u32 get_ftdi_divisor(struct tty_struct *tty, > __func__, priv->custom_divisor, baud); > } > > + if (!baud) > + baud = old_baud; > if (!baud) > baud = 9600; This looks like it breaks B0 handling. Either way, an unrelated change. > switch (priv->chip_type) { > @@ -1330,8 +1332,12 @@ static u32 get_ftdi_divisor(struct tty_struct *tty, > if (div_value == -1) { > dev_dbg(dev, "%s - Baudrate (%d) requested is not supported\n", > __func__, baud); > - baud = 9600; > + baud = old_baud ? old_baud : 9600; > div_value = ftdi_sio_baud_to_divisor(baud); > + if (div_value == -1) { > + baud = 9600; > + div_value = ftdi_sio_baud_to_divisor(baud); > + } > div_okay = 0; > } > break; > @@ -1340,8 +1346,8 @@ static u32 get_ftdi_divisor(struct tty_struct *tty, > div_value = ftdi_232am_baud_to_divisor(baud); > } else { > dev_dbg(dev, "%s - Baud rate too high!\n", __func__); > - baud = 9600; > - div_value = ftdi_232am_baud_to_divisor(9600); > + baud = (old_baud >= 183 && old_baud <= 3000000) ? old_baud : 9600; And please avoid using the ternary operator which tend to just hurt readability. Looks like this needs to be refactored in some way. > @@ -1525,7 +1536,7 @@ static int set_serial_info(struct tty_struct *tty, struct serial_struct *ss) > if (priv->flags & ASYNC_SPD_MASK) > dev_warn_ratelimited(&port->dev, "use of SPD flags is deprecated\n"); > > - change_speed(tty, port); > + change_speed(tty, port, 0); Zero has a special meaning (B0). > } > mutex_unlock(&priv->cfg_lock); > return 0; > @@ -2774,9 +2785,12 @@ static void ftdi_set_termios(struct tty_struct *tty, > /* Drop RTS and DTR */ > clear_mctrl(port, TIOCM_DTR | TIOCM_RTS); > } else { > + speed_t old_baud = > + old_termios ? tty_termios_baud_rate(old_termios) : 0; Just use 9600 if you don't have an old termios. The termios rate should be valid in that case. Johan