linux-kernel - Re: [PATCH] sh: maple: add support for Maple controller as a joystick

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <11B1B6AB-D879-4BB9-AE05-C5025B449CA1@gmail.com>
Date:	Sat, 20 Dec 2008 14:17:25 -0800
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Adrian McMenamin <adrian@...golddream.dyndns.info>
Cc:	Matt Fleming <matt@...sole-pimps.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-sh <linux-sh@...r.kernel.org>,
	Andrew Morton <akpm@...l.org>, Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH] sh: maple: add support for Maple controller as a joystick

On Dec 20, 2008, at 12:47 PM, Adrian McMenamin <adrian@...golddream.dyndns.info 
 > wrote:

> On Sat, 2008-12-20 at 12:19 -0800, Dmitry Torokhov wrote:
>> On Saturday 20 December 2008 08:07:27 Adrian McMenamin wrote:
>>> On Sat, 2008-12-20 at 15:16 +0000, Matt Fleming wrote:
>>>> On Fri, Dec 19, 2008 at 11:15:42PM +0000, Adrian McMenamin wrote:
>>>>> Add support for the SEGA Dreamcast Maple controller as a joystick
>>>>
>>>> [snip]
>>>>
>>>>> +    struct dc_pad *pad = maple_get_drvdata(mapledev);
>>>>> +    struct input_dev *dev = pad->dev;
>>>>> +    unsigned char *res = mq->recvbuf;
>>>>> +
>>>>> +    buttons = ~cpu_to_le16(*(unsigned short *)(res + 8));
>>>>> +
>>>>
>>>> I may be wrong but shouldn't this use the I/O accessor functions?
>>>
>>> It's not iomemory, so I don't think so. The maple bus writes to a  
>>> buffer
>>> in the physical RAM.
>>>
>>
>> Hmm, but why we are going _from_ cpu order to le16??? I'd expect we
>> wanted to do conversion the other way around. I pulled it out of  
>> 'next'
>> for now.
>>
> The data is transmitted here by the bus in 32 bit little endian blocks
> but makes sense in le16 bit lumps. Off is 1 and on is 0 - hence the ~
>
> The first 16 bits are the button data the next 16 bits are the (start
> of) the axis data. Both cpu and bus data (in this case - it can vary)
> are little endian.

Right, so I think we need le16_to_cpu here, you want the data in  
native CPU order to manipulate it.

-- 
Dmitry

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/