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From: Johan Hovold <johan@kernel.org>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Johan Hovold <johan@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	linux-usb@vger.kernel.org,
	Thomas Winischhofer <thomas@winischhofer.net>,
	"Ahmed S. Darwish" <a.darwish@linutronix.de>,
	Mathias Nyman <mathias.nyman@intel.com>,
	Valentina Manea <valentina.manea.m@gmail.com>,
	Shuah Khan <shuah@kernel.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	linux-omap@vger.kernel.org, Kukjin Kim <kgene@kernel.org>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org,
	Felipe Balbi <balbi@kernel.org>,
	Duncan Sands <duncan.sands@free.fr>
Subject: Re: [patch V2 03/13] USB: serial: keyspan_pda: Consolidate room query
Date: Sun, 25 Oct 2020 18:05:45 +0100	[thread overview]
Message-ID: <20201025170545.GS26280@localhost> (raw)
In-Reply-To: <20201019101109.903651690@linutronix.de>

On Mon, Oct 19, 2020 at 12:06:32PM +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.

As Alan pointed out, this buffer is in fact required and not pointless
at all even if reallocating it may be suboptimal.

Note however that there are several further allocations done by
usb_control_msg() for each control request.

> Allocate a byte buffer at init which can be used instead. The buffer is
> only used in open() and tty->write(). 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.

As I mentioned in my comments to the previous patch, I've rewritten the
driver so that is no longer does this query in the write path. I kept
the buffer allocation for now though in case you want to rework this one
top.

Johan

  reply	other threads:[~2020-10-25 17:05 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-19 10:06 [patch V2 00/13] USB: Cleanup in_interupt/in_irq/in_atomic() usage Thomas Gleixner
2020-10-19 10:06 ` [patch V2 01/13] USB: sisusbvga: Make console support depend on BROKEN Thomas Gleixner
2020-10-19 10:06 ` [patch V2 02/13] USB: serial: keyspan_pda: Replace in_interrupt() usage Thomas Gleixner
2020-10-25 16:56   ` Johan Hovold
2020-10-26 12:47     ` Sebastian Andrzej Siewior
2020-10-27  8:16       ` Johan Hovold
2020-10-19 10:06 ` [patch V2 03/13] USB: serial: keyspan_pda: Consolidate room query Thomas Gleixner
2020-10-25 17:05   ` Johan Hovold [this message]
2020-10-19 10:06 ` [patch V2 04/13] USB: serial: digi_acceleport: Remove in_interrupt() usage Thomas Gleixner
2020-10-25 17:16   ` Johan Hovold
2020-10-26 14:03     ` [PATCH v3 04/13 ] " Sebastian Andrzej Siewior
2020-10-27  8:26       ` Johan Hovold
2020-10-19 10:06 ` [patch V2 05/13] usb: xhci: Remove in_interrupt() checks Thomas Gleixner
2020-10-19 10:06 ` [patch V2 06/13] usb: host: isp1362: Replace in_interrupt() usage Thomas Gleixner
2020-10-28 11:27   ` Greg Kroah-Hartman
2020-10-19 10:06 ` [patch V2 07/13] usbip: Remove in_interrupt() check Thomas Gleixner
2020-10-19 10:06 ` [patch V2 08/13] usb: hosts: Remove in_interrupt() from comments Thomas Gleixner
2020-10-19 16:28   ` Alan Stern
2020-10-19 10:06 ` [patch V2 09/13] USB: host: ehci-pmcmsp: Cleanup usb_hcd_msp_remove() Thomas Gleixner
2020-10-19 16:28   ` Alan Stern
2020-10-19 10:06 ` [patch V2 10/13] usb: gadget: pxa27x_udc: Replace in_interrupt() usage in comments Thomas Gleixner
2020-10-19 10:06 ` [patch V2 11/13] usb: gadget: udc: Remove in_interrupt()/in_irq() from comments Thomas Gleixner
2020-10-19 16:28   ` Alan Stern
2020-10-19 10:06 ` [patch V2 12/13] usb: core: Replace in_interrupt() in comments Thomas Gleixner
2020-10-19 16:28   ` Alan Stern
2020-10-19 10:06 ` [patch V2 13/13] usb: atm: Replace in_interrupt() usage in comment Thomas Gleixner
2020-10-19 10:28   ` Duncan Sands

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