linux-kernel - Re: [PATCH v1] Input: elants_i2c: Add Elan touchscreen support

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Message-ID: <20141120203523.GC14798@dtor-glaptop>
Date:	Thu, 20 Nov 2014 12:35:23 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Oliver Neukum <oneukum@...e.de>
Cc:	scott <scott.liu@....com.tw>, linux-kernel@...r.kernel.org,
	linux-input@...r.kernel.org,
	Vincent Wang <vincent.wang@....com.tw>,
	Jeff Chuang <jeff.chuang@....com.tw>,
	Benson Leung <bleung@...omium.org>,
	Benjamin Tissoires <benjamin.tissoires@...il.com>,
	Henrik Rydberg <rydberg@...omail.se>,
	David Herrmann <dh.herrmann@...il.com>
Subject: Re: [PATCH v1] Input: elants_i2c: Add Elan touchscreen support

On Thu, Nov 20, 2014 at 09:27:35PM +0100, Oliver Neukum wrote:
> On Thu, 2014-11-20 at 09:47 -0800, Dmitry Torokhov wrote:
> > Hi Oliver,
> > 
> > On Thu, Nov 20, 2014 at 11:31:30AM +0100, Oliver Neukum wrote:
> > > > +static int elants_i2c_initialize(struct elants_data *ts)
> > > > +{
> > > > +       struct i2c_client *client = ts->client;
> > > > +       int error, retry_cnt;
> > > > +       const u8 hello_packet[] = { 0x55, 0x55, 0x55, 0x55 };
> > > > +       const u8 recov_packet[] = { 0x55, 0x55, 0x80, 0x80 };
> > > > +       u8 buf[HEADER_SIZE];
> > > > +
> > > 
> > > Strictly speaking you should disable preemption here.
> > 
> > Umm, why?
> 
> You said the upper bound matters. So you need to protect yourself
> against losing too much time by preemption.

We are using i2c so we can't really disable preemption here... I think
we  have enough slack, although I would indeed lower the sleep time.
I'll let Scott comment on that.

Thanks.

-- 
Dmitry
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