linux-kernel - RE: [linux-nfc] [PATCH RFC] nfc: add a driver for pn532 connected on uart

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Message-ID: <A4DEEF93D8D14A418311321B77DB71E9C9E299@IRSMSX104.ger.corp.intel.com>
Date:	Fri, 23 Aug 2013 09:47:57 +0000
From:	"Rymarkiewicz, WaldemarX" <waldemarx.rymarkiewicz@...el.com>
To:	Lars Poeschel <poeschel@...onage.de>
CC:	Lars Poeschel <larsi@....tu-dresden.de>,
	"sameo@...ux.intel.com" <sameo@...ux.intel.com>,
	"jslaby@...e.cz" <jslaby@...e.cz>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-wireless@...r.kernel.org" <linux-wireless@...r.kernel.org>,
	"linux-nfc@...ts.01.org" <linux-nfc@...ts.01.org>
Subject: RE: [linux-nfc] [PATCH RFC] nfc: add a driver for pn532 connected
 on uart

Hi,

>Yes, I know that and I explicitly mentioned that. I had to get this chip working
>somehow and I had to begin somewhere. The pn533 driver is really very hard 
>to understand with it's massive use of nested callbacks, workqueues and
>usb urbs. So I took the approach to try to understand what happens while modifying
>and would then later factor out what both drivers have in common.
>The other way is understanding the code first and then decide what would be needed for
> both chips, factor that out and then write the pn532 uart specific stuff. And this uart stuff
>is a pain itself in linux. This way seemed much harder to me,
> especially as I have no pn533 device to test which things will break.

I understand. It took me some time to understand this too. Now, it's even harder after adding  protocol ops, but still is pretty well layered. 

> I suggest to separate transport layer from the core in pn533 and add 
> support for uart and usb separately. This is exactly what I've planned 
> while changing pn533 to support acr122 device.
>> Yes, I agree with you this should be done. I'll expect it to be challenging
>> but based on my previous work this could be doable. 

Be sure there will be pitfalls separating transport.  I've already experienced some of them adding support for acr122. 

>> I'll look into that in my next free timeslot. I'll not be able to do that in the next two months. 
>>Sorry.

No worries. I know this pain :) 

Thanks,
/Waldek
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