linux-kernel - Re: [RFT/PATCH] i8042: remove polling timer (v6)

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Message-ID: <d120d5000611030608v726b5459y743703179d079ae5@mail.gmail.com>
Date:	Fri, 3 Nov 2006 09:08:47 -0500
From:	"Dmitry Torokhov" <dmitry.torokhov@...il.com>
To:	"Vojtech Pavlik" <vojtech@...e.cz>
Cc:	"Dave Neuer" <mr.fred.smoothie@...ox.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...l.org>
Subject: Re: [RFT/PATCH] i8042: remove polling timer (v6)

On 11/3/06, Vojtech Pavlik <vojtech@...e.cz> wrote:
> On Fri, Nov 03, 2006 at 12:56:02AM -0500, Dmitry Torokhov wrote:
> > On Monday 30 October 2006 09:22, Dave Neuer wrote:
> > > On 10/30/06, Dave Neuer <mr.fred.smoothie@...ox.com> wrote:
> > > >
> > > > Maybe I'm missing something, (well actually I'm sure I'm missing
> > > > somethng). Looking at the code again, it's unclear to me why there is
> > > > even a call to the ISR in i8042_aux_write, since the latter function
> > > > already calls i8042_read_data.
> > > >
> > >
> > > Whoops, sorry. I meant i8042_command, which is called by
> > > i8042_aux_write before the call to i8042_interrupt, already calls
> > > i8042_read_data.
> > >
> >
> > It only calls i8042_read_data() if command is supposed to return data.
> > Neither I8042_CMD_AUX_SEND nor I8042_CMD_MUX_SEND wait fotr data to come
> > back.
> >
> > Anyway, I removed call to i8042_interrupt() from i8042_aux_write() because
> > it is indeed unnecessary.
>
> It was there because some older i8042's will report an error byte (=>
> data) even though no device is connected, not just set error flags.
>
> The unflushed byte in the FIFO then caused problems later on.
>
> It may be that now it'll get disposed of correctly, I haven't looked at
> the code for a while.
>

By the time serio ports are registered and there are potential users
of i8042_aux_write() we already requested AUX IRQ and I believe any
arriving data should be automatically disposed through irq handler. It
wasn't the case before, when we postponed requesting IRQ until the
port was opened...

-- 
Dmitry
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