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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 220F8C43457 for ; Wed, 14 Oct 2020 16:14:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C5CB4214D8 for ; Wed, 14 Oct 2020 16:14:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728178AbgJNQOe (ORCPT ); Wed, 14 Oct 2020 12:14:34 -0400 Received: from netrider.rowland.org ([192.131.102.5]:55587 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1730423AbgJNQOe (ORCPT ); Wed, 14 Oct 2020 12:14:34 -0400 Received: (qmail 718746 invoked by uid 1000); 14 Oct 2020 12:14:33 -0400 Date: Wed, 14 Oct 2020 12:14:33 -0400 From: Alan Stern To: Thomas Gleixner Cc: LKML , Peter Zijlstra , Sebastian Andrzej Siewior , Johan Hovold , Greg Kroah-Hartman , linux-usb@vger.kernel.org, Thomas Winischhofer , "Ahmed S. Darwish" , Mathias Nyman , Valentina Manea , Shuah Khan , linux-omap@vger.kernel.org, Kukjin Kim , Krzysztof Kozlowski , linux-arm-kernel@lists.infradead.org, linux-samsung-soc@vger.kernel.org, Felipe Balbi , Duncan Sands Subject: Re: [patch 03/12] USB: serial: keyspan_pda: Consolidate room query Message-ID: <20201014161433.GB712494@rowland.harvard.edu> References: <20201014145215.518912759@linutronix.de> <20201014145727.338773481@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201014145727.338773481@linutronix.de> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-omap@vger.kernel.org On Wed, Oct 14, 2020 at 04:52:18PM +0200, Thomas Gleixner wrote: > From: Sebastian Andrzej Siewior > > Having two copies of the same code doesn't make the code more readable and > allocating a buffer of 1 byte for a synchronous operation is a pointless > exercise. Not so. In fact, it is required, because a portion of a structure cannot be mapped for DMA unless it is aligned at a cache line boundary. > Add a byte buffer to struct keyspan_pda_private which can be used > instead. The buffer is only used in open() and tty->write(). This won't work. > Console writes > are not calling into the query. open() obviously happens before write() and > the writes are serialized by bit 0 of port->write_urbs_free which protects > also the transaction itself. > > Move the actual query into a helper function and cleanup the usage sites in > keyspan_pda_write() and keyspan_pda_open(). > > Signed-off-by: Sebastian Andrzej Siewior > Signed-off-by: Thomas Gleixner > Cc: Johan Hovold > Cc: Greg Kroah-Hartman > Cc: linux-usb@vger.kernel.org > --- > drivers/usb/serial/keyspan_pda.c | 102 ++++++++++++++++----------------------- > 1 file changed, 43 insertions(+), 59 deletions(-) > > --- a/drivers/usb/serial/keyspan_pda.c > +++ b/drivers/usb/serial/keyspan_pda.c > @@ -47,6 +47,7 @@ struct keyspan_pda_private { > struct work_struct unthrottle_work; > struct usb_serial *serial; > struct usb_serial_port *port; > + u8 query_buf; > }; > > > @@ -436,6 +437,31 @@ static int keyspan_pda_tiocmset(struct t > return rc; > } > > +/* > + * Using priv->query_buf is safe here because this is only called for TTY > + * operations open() and write(). write() comes post open() obviously and > + * write() itself is serialized via bit 0 of port->write_urbs_free. Console > + * writes are never calling into this. > + */ > +static int keyspan_pda_query_room(struct usb_serial *serial, > + struct keyspan_pda_private *priv) > +{ > + int res; > + > + res = usb_control_msg(serial->dev, usb_rcvctrlpipe(serial->dev, 0), > + 6, /* write_room */ > + USB_TYPE_VENDOR | USB_RECIP_INTERFACE | USB_DIR_IN, > + 0, /* value */ > + 0, /* index */ > + &priv->query_buf, > + 1, > + 2000); Instead, consider using the new usb_control_msg_recv() API. But it might be better to allocate the buffer once and for all. Alan Stern