linux-kernel - Re: [PATCH 03/14 v3] Input: atmel_mxt_ts - refactor mxt_read/write

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Date:	Tue, 8 May 2012 22:50:09 -0700
From:	Dmitry Torokhov <dmitry.torokhov@...il.com>
To:	Henrik Rydberg <rydberg@...omail.se>
Cc:	Daniel Kurtz <djkurtz@...omium.org>,
	Joonyoung Shim <jy0922.shim@...sung.com>,
	Nick Dyer <nick.dyer@...ev.co.uk>, linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org, Benson Leung <bleung@...omium.org>,
	Yufeng Shen <miletus@...omium.org>
Subject: Re: [PATCH 03/14 v3] Input: atmel_mxt_ts - refactor
 mxt_read/write_reg to take a length

Hi Henrik,

On Tue, Apr 24, 2012 at 01:23:19PM +0200, Henrik Rydberg wrote:
> Hi Daniel,
> 
> > The i2c bus requires 5 bytes to do a 1 byte read (1-byte i2c address + 2
> > byte offset + 1-byte i2c address + 1 byte data), or 4 bytes to do a
> > 1-byte write (1 byte i2c address + 2 byte offset + 1 byte data).
> > 
> > By taking a length with reads and writes, the driver can amortize
> > transaction overhead by performing larger transactions where appropriate.
> > 
> > This patch just sets up the new API.  Later patches refactor reads/writes
> > to take advantage of the larger transactions.
> > 
> > These functions are also now return any errors reported by the i2c layer.
> > 
> > Signed-off-by: Daniel Kurtz <djkurtz@...omium.org>
> > ---
> 
> In the cyttsp a dedicate tx buffer is used, which is a bit easier on
> the eyes.

Cyttsp needs a cacheline aligned buffer because it can be wired over
SPI, that is why it has a dedicate buffer.

-- 
Dmitry
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