linux-kernel - Re: [PATCH v6.1 1/1] Input: Add userio module

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Date:	Fri, 2 Oct 2015 10:37:14 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	cpaul@...hat.com
Cc:	David Herrmann <dh.herrmann@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-input@...r.kernel.org, linux-api@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Arnd Bergmann <arnd@...db.de>, Joe Perches <joe@...ches.com>,
	Jiri Slaby <jslaby@...e.com>,
	Vishnu Patekar <vishnupatekar0510@...il.com>,
	Sebastian Ott <sebott@...ux.vnet.ibm.com>,
	Benjamin Tissoires <benjamin.tissoires@...hat.com>,
	Hans de Goede <hdegoede@...hat.com>,
	linux-doc@...r.kernel.org
Subject: Re: [PATCH v6.1 1/1] Input: Add userio module

On Wed, Sep 23, 2015 at 01:54:59PM -0400, cpaul@...hat.com wrote:
> +static int userio_device_write(struct serio *id, unsigned char val)
> +{
> +	struct userio_device *userio = id->port_data;
> +	unsigned long flags;
> +
> +	if (!userio)
> +		return -1;

I still have the same question: how can this happen? Where do we reset
port data to NULL? What happens if we set to NULL after checking?

> +
> +	spin_lock_irqsave(&userio->buf_lock, flags);
> +
> +	userio->buf[userio->head] = val;
> +	userio->head = (userio->head + 1) % USERIO_BUFSIZE;
> +
> +	if (userio->head == userio->tail)
> +		dev_warn(userio_misc.this_device,
> +			 "Buffer overflowed, userio client isn't keeping up");
> +
> +	spin_unlock_irqrestore(&userio->buf_lock, flags);
> +
> +	wake_up_interruptible(&userio->waitq);
> +
> +	return 0;
> +}

Thanks.

-- 
Dmitry
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