linux-kernel - Re: [RFC PATCH 01/06] input/rmi4: Public header and documentation

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Date:	Tue, 23 Oct 2012 15:47:28 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Christopher Heiny <cheiny@...aptics.com>
Cc:	Jean Delvare <khali@...ux-fr.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Linux Input <linux-input@...r.kernel.org>,
	Allie Xiong <axiong@...aptics.com>,
	Vivian Ly <vly@...aptics.com>,
	Daniel Rosenberg <daniel.rosenberg@...aptics.com>,
	Alexandra Chen <alexandra.chen@...synaptics.com>,
	Joerie de Gram <j.de.gram@...il.com>,
	Wolfram Sang <w.sang@...gutronix.de>,
	Mathieu Poirier <mathieu.poirier@...aro.org>,
	Linus Walleij <linus.walleij@...ricsson.com>,
	Naveen Kumar Gaddipati <naveen.gaddipati@...ricsson.com>
Subject: Re: [RFC PATCH 01/06] input/rmi4: Public header and documentation

On Tuesday, October 23, 2012 03:39:00 PM Christopher Heiny wrote:
> On 10/11/2012 01:20 AM, Dmitry Torokhov wrote:
> > On Fri, Oct 05, 2012 at 09:09:58PM -0700, Christopher Heiny wrote:
> >> +
> >> +	int (*write_block)(struct rmi_phys_device *phys, u16 addr, u8 *buf,
> >> +			   int len);
> >> +	int (*read_block)(struct rmi_phys_device *phys, u16 addr, u8 *buf,
> >> +			  int len);
> >> +
> > 
> > If you declare your buffer as [const] void * instead of u8 * I think you
> > will be able to get rid of most of your unions.
> 
> Good point.  We'll explore that.  If you see it in the next patch,
> you'll know it worked out.
> 
> >> + * Helper fn to convert a byte array representing a 16 bit value in the
> >> RMI + * endian-ness to a 16-bit value in the native processor's specific
> >> endianness. + * We don't use ntohs/htons here because, well, we're not
> >> dealing with + * a pair of 16 bit values. Casting dest to u16* wouldn't
> >> work, because + * that would imply knowing the byte order of u16 in the
> >> first place.  The + * same applies for using shifts and masks.
> >> + */
> >> +static inline u16 batohs(u8 *src)
> >> +{
> >> +	return src[1] * 0x100 + src[0];
> >> +}
> >> +
> >> +/**
> >> + * Helper function to convert a 16 bit value (in host processor
> >> endianess) to + * a byte array in the RMI endianess for u16s.  See above
> >> comment for + * why we dont us htons or something like that.
> >> + */
> >> +static inline void hstoba(u8 *dest, u16 src)
> >> +{
> >> +	dest[0] = src % 0x100;
> >> +	dest[1] = src / 0x100;
> >> +}
> > 
> > These are not used anymore, right?
> 
> There are function drivers that we chose not to include that depend on
> these.  We'll drop these from rmi.h until we're ready to submit those
> other function drivers.

OK, in this case, like last time we discussed, your function drivers
should use cpu_to_le16() and le16_to_cpu() instead.

Thanks.

-- 
Dmitry
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