linux-kernel - Re: [RFC ebeam PATCH v3 0/2]

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Message-ID: <50207357.5080208@laposte.net>
Date:	Tue, 07 Aug 2012 03:45:59 +0200
From:	Yann Cantin <yann.cantin@...oste.net>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
CC:	Greg KH <gregkh@...uxfoundation.org>, linux-input@...r.kernel.org,
	linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC ebeam PATCH v3 0/2]

Le 07/08/2012 00:09, Dmitry Torokhov a écrit :
> On Monday, August 06, 2012 02:44:23 PM Greg KH wrote:
>> On Mon, Aug 06, 2012 at 11:21:42PM +0200, Yann Cantin wrote:
>>> Hi,
>>>
>>> New USB input driver for eBeam devices.
>>>
>>> Currently, only the Luidia eBeam classic projection model is supported.
>>> Edge model and a NEC interactive video-projector support planned for the
>>> end of the mounth.
>>>
>>> Patch 1 to blacklist the device for hid generic-usb.
>>>
>>> Patch 2 is the actual driver.
>>>
>>> Changes from previous :
>>> - switch to div64_s64 for portable 64/64-bits divisions
> 
> Do you really need this much precision? It will be slower on 32 bits..

Yes. I can give the details if you want (homography computation without
floating point maths).

>>> - some cosmetics in device name
>>> - unused include and def removed
>>> - variables name changes for readability
>>>
>>> Pending issues :
>>>
>>> - sysfs custom files : need to pass 13 parameters for calibration :
>>>   choice is between lots of simply-handled, or few with a big sscanf.
>>
>> sysfs is "one value per file", so use lots of different files please.
> 
> This is kind of a "one value" though - it is a transformation matrix.
> Maybe switch it to binary - 9 s32?

Right, but this somehow obfuscate the api. In the other hand, i doubt
there will be lots of calibration tools other that mine.

Is there any drawback for numerous sysfs custom files ?

-- 
Yann Cantin
A4FEB47F
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