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

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Message-ID: <20120424112319.GA9688@polaris.bitmath.org>
Date:	Tue, 24 Apr 2012 13:23:19 +0200
From:	"Henrik Rydberg" <rydberg@...omail.se>
To:	Daniel Kurtz <djkurtz@...omium.org>
Cc:	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	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 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. OTOH, the write operation seems infrequent enough to not
matter much, so

    Acked-by: Henrik Rydberg <rydberg@...omail.se>

Thanks for your patience,
Henrik
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