linux-kernel - Re: [PATCH 2/2] media: rc: add driver for IR remote receiver on MT7623 SoC

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Message-ID: <1483931601.16976.48.camel@mtkswgap22>
Date:   Mon, 9 Jan 2017 11:13:21 +0800
From:   Sean Wang <sean.wang@...iatek.com>
To:     Sean Young <sean@...s.org>
CC:     <mchehab@....samsung.com>, <hdegoede@...hat.com>,
        <hkallweit1@...il.com>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <matthias.bgg@...il.com>,
        <andi.shyti@...sung.com>, <hverkuil@...all.nl>,
        <ivo.g.dimitrov.75@...il.com>, <linux-media@...r.kernel.org>,
        <devicetree@...r.kernel.org>, <linux-mediatek@...ts.infradead.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <keyhaede@...il.com>
Subject: Re: [PATCH 2/2] media: rc: add driver for IR remote receiver on
 MT7623 SoC

On Sun, 2017-01-08 at 21:16 +0000, Sean Young wrote:
> Hi Sean,
> 
> On Fri, Jan 06, 2017 at 03:31:25PM +0800, Sean Wang wrote:
> > On Thu, 2017-01-05 at 17:12 +0000, Sean Young wrote:
> > > On Fri, Jan 06, 2017 at 12:06:24AM +0800, sean.wang@...iatek.com wrote:
> > > > +	/* Handle pulse and space until end of message */
> > > > +	for (i = 0 ; i < MTK_CHKDATA_SZ ; i++) {
> > > > +		val = mtk_r32(ir, MTK_CHKDATA_REG(i));
> > > > +		dev_dbg(ir->dev, "@reg%d=0x%08x\n", i, val);
> > > > +
> > > > +		for (j = 0 ; j < 4 ; j++) {
> > > > +			wid = (val & (0xff << j * 8)) >> j * 8;
> > > > +			rawir.pulse = !rawir.pulse;
> > > > +			rawir.duration = wid * (MTK_IR_SAMPLE + 1);
> > > > +			ir_raw_event_store_with_filter(ir->rc, &rawir);
> > > > +
> > > > +			if (MTK_IR_END(wid))
> > > > +				goto end_msg;
> > > > +		}
> > > > +	}
> > > 
> > > If I read this correctly, there is a maximum of 17 * 4 = 68 edges per
> > > IR message. The rc6 mce key 0 (scancode 0x800f0400) is 69 edges, so that
> > > won't work.
> > > 
> > Uh, this is related to hardware limitation. Maximum number hardware
> > holds indeed is only 68 edges as you said :( 
> > 
> > For the case, I will try change the logic into that the whole message 
> > is dropped if no end of message is seen within 68 counts to avoid
> > wasting CPU for decoding. 
> 
> I'm not sure it is worthwhile dropping the IR in that case. The processing
> is minimal and it might be possible that we have just enough IR to decode
> a scancode even if the trailing end of message is missing. Note that
> the call to ir_raw_event_set_idle() will generate an timeout IR event, so
> there will always be an end of message marker.


1)
I agree with you :) The original logic I made already as you pointed out
is sent incomplete IR message to let ir-raw try to decode as possible.

2)
I had another question. I found multiple and same IR messages being
received when using SONY remote controller. Should driver needs to
report each message or only one of these to the upper layer ?


> All I wanted to do was point out a limitation in case there is a
> workaround; if there is not then we might as well make do with the IR
> we do have.

I also will leave some words about limitation we had in the comments.

> Thanks
> Sean