From: Alan Stern <stern@rowland.harvard.edu>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Felipe Balbi <balbi@kernel.org>,
Thomas Winischhofer <thomas@winischhofer.net>,
Mathias Nyman <mathias.nyman@intel.com>,
Peter Zijlstra <peterz@infradead.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
linux-usb@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
Krzysztof Kozlowski <krzk@kernel.org>,
Johan Hovold <johan@kernel.org>,
linux-samsung-soc@vger.kernel.org, Kukjin Kim <kgene@kernel.org>,
Valentina Manea <valentina.manea.m@gmail.com>,
Duncan Sands <duncan.sands@free.fr>,
"Ahmed S. Darwish" <a.darwish@linutronix.de>,
linux-omap@vger.kernel.org, Shuah Khan <shuah@kernel.org>,
linux-arm-kernel@lists.infradead.org
Subject: Re: [patch 03/12] USB: serial: keyspan_pda: Consolidate room query
Date: Wed, 14 Oct 2020 12:14:33 -0400 [thread overview]
Message-ID: <20201014161433.GB712494@rowland.harvard.edu> (raw)
In-Reply-To: <20201014145727.338773481@linutronix.de>
On Wed, Oct 14, 2020 at 04:52:18PM +0200, Thomas Gleixner wrote:
> From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
>
> 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 <bigeasy@linutronix.de>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> Cc: Johan Hovold <johan@kernel.org>
> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 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
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2020-10-14 16:16 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-14 14:52 [patch 00/12] UBS: Cleanup in_interupt/in_irq/in_atomic() usage Thomas Gleixner
2020-10-14 14:52 ` [patch 02/12] USB: serial: keyspan_pda: Replace in_interrupt() usage Thomas Gleixner
2020-10-14 14:52 ` [patch 03/12] USB: serial: keyspan_pda: Consolidate room query Thomas Gleixner
2020-10-14 16:14 ` Alan Stern [this message]
2020-10-14 16:17 ` Thomas Gleixner
2020-10-14 16:27 ` Sebastian Andrzej Siewior
2020-10-14 16:34 ` Alan Stern
2020-10-14 16:44 ` Sebastian Andrzej Siewior
2020-10-14 14:52 ` [patch 04/12] USB: serial: digi_acceleport: Remove in_interrupt() usage Thomas Gleixner
2020-10-14 14:52 ` [patch 05/12] usb: xhci: Remove in_interrupt() checks Thomas Gleixner
2020-10-23 13:38 ` Mathias Nyman
2020-10-14 14:52 ` [patch 06/12] usb: host: isp1362: Replace in_interrupt() usage Thomas Gleixner
2020-10-14 14:52 ` [patch 07/12] usbip: Remove in_interrupt() check Thomas Gleixner
2020-10-14 15:45 ` Shuah Khan
2020-10-14 14:52 ` [patch 08/12] usb: hosts: Remove in_interrupt() from comments Thomas Gleixner
2020-10-14 15:24 ` Krzysztof Kozlowski
2020-10-14 16:20 ` Alan Stern
2020-10-14 14:52 ` [patch 09/12] usb: gadget: pxa27x_udc: Replace in_interrupt() usage in comments Thomas Gleixner
2020-10-14 14:52 ` [patch 10/12] usb: gadget: udc: Remove in_interrupt()/in_irq() from comments Thomas Gleixner
2020-10-14 16:22 ` Alan Stern
2020-10-14 14:52 ` [patch 11/12] usb: core: Replace in_interrupt() in comments Thomas Gleixner
2020-10-14 16:27 ` Alan Stern
2020-10-14 16:41 ` Sebastian Andrzej Siewior
2020-10-14 18:13 ` Alan Stern
2020-10-14 14:52 ` [patch 12/12] usb: atm: Replace in_interrupt() usage in comment Thomas Gleixner
2020-10-23 8:01 ` [patch 00/12] UBS: Cleanup in_interupt/in_irq/in_atomic() usage Pavel Machek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20201014161433.GB712494@rowland.harvard.edu \
--to=stern@rowland.harvard.edu \
--cc=a.darwish@linutronix.de \
--cc=balbi@kernel.org \
--cc=bigeasy@linutronix.de \
--cc=duncan.sands@free.fr \
--cc=gregkh@linuxfoundation.org \
--cc=johan@kernel.org \
--cc=kgene@kernel.org \
--cc=krzk@kernel.org \
--cc=linux-arm-kernel@lists.infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-omap@vger.kernel.org \
--cc=linux-samsung-soc@vger.kernel.org \
--cc=linux-usb@vger.kernel.org \
--cc=mathias.nyman@intel.com \
--cc=peterz@infradead.org \
--cc=shuah@kernel.org \
--cc=tglx@linutronix.de \
--cc=thomas@winischhofer.net \
--cc=valentina.manea.m@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).