linux-kernel - Re: [PATCH v4 2/2] I2C: mediatek: Add driver for MediaTek I2C controller

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Date:	Wed, 21 Jan 2015 16:34:35 +0800
From:	Eddie Huang <eddie.huang@...iatek.com>
To:	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
CC:	Wolfram Sang <wsa@...-dreams.de>,
	Matthias Brugger <matthias.bgg@...il.com>,
	<srv_heupstream@...iatek.com>, Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	Grant Likely <grant.likely@...aro.org>,
	Jean Delvare <jdelvare@...e.de>, Arnd Bergmann <arnd@...db.de>,
	Doug Anderson <dianders@...omium.org>,
	Andrew Bresticker <abrestic@...omium.org>,
	Max Schwarz <max.schwarz@...ine.de>,
	Boris BREZILLON <boris.brezillon@...e-electrons.com>,
	Anders Berg <anders.berg@...gotech.com>,
	Neelesh Gupta <neelegup@...ux.vnet.ibm.com>,
	Wei Yan <sledge.yanwei@...wei.com>,
	Lee Jones <lee.jones@...aro.org>,
	Simon Glass <sjg@...omium.org>,
	Jim Cromie <jim.cromie@...il.com>,
	Bjorn Andersson <bjorn.andersson@...ymobile.com>,
	Beniamino Galvani <b.galvani@...il.com>,
	Xudong Chen <xudong.chen@...iatek.com>,
	<linux-i2c@...r.kernel.org>, <devicetree@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<yingjoe.chen@...iatek.com>, <yh.chen@...iatek.com>,
	Sascha Hauer <kernel@...gutronix.de>
Subject: Re: [PATCH v4 2/2] I2C: mediatek: Add driver for MediaTek I2C
 controller

Hi Uwe,

On Wed, 2015-01-21 at 09:20 +0100, Uwe Kleine-König wrote:
> Hello,
> 
> On Wed, Jan 21, 2015 at 11:13:24AM +0800, Eddie Huang wrote:
> > > > +	/* set when doing the transfer */
> > > > +	u16 irq_stat;			/* interrupt status */
> > > > +	unsigned int speed_hz;		/* The speed in transfer */
> > > > +	bool trans_stop;		/* i2c transfer stop */
> > > > +	enum mtk_trans_op op;
> > > > +	u16 msg_len;
> > > > +	u8 *msg_buf;			/* pointer to msg data */
> > > > +	u16 msg_aux_len;		/* WRRD mode to set AUX_LEN register*/
> > > > +	u16 addr;	/* 7bit slave address, without read/write bit */
> > > Wouldn't it be easier to maintain a pointer to the message to be
> > > transferred?
> > I think use mtk_i2c pointer is more flexible than maintain a pointer to
> > message.
> Not sure you understood what I intended to suggest. My idea was to drop
> 
> 	u16 msg_len;
> 	u8 *msg_buf;
> 	u16 msg_aux_len; // maybe
> 	u16 addr;
> 
> from struct mtk_i2c and add a struct i2c_msg *msg instead. Up to you to
> decide.
> 
Because this driver pass mtk_i2c pointer between functions, it's
flexible to use any member of struct mtk_i2c. The good thing is avoid
passing one more struct i2c_msg parameter between functions, or another
struct copy. The bad thing is make struct mtk_i2c larger. I prefer to
keep as it is now.

Best Regards
Eddie


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