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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/
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