linux-kernel - Re: [PATCH v9 2/7] i2c: Add FSI-attached I2C master algorithm

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Date:   Tue, 05 Jun 2018 09:38:06 +1000
From:   Benjamin Herrenschmidt <benh@...nel.crashing.org>
To:     Andy Shevchenko <andy.shevchenko@...il.com>,
        Eddie James <eajames@...ux.vnet.ibm.com>
Cc:     linux-i2c <linux-i2c@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Rob Herring <robh+dt@...nel.org>,
        Joel Stanley <joel@....id.au>,
        Mark Rutland <mark.rutland@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Randy Dunlap <rdunlap@...radead.org>
Subject: Re: [PATCH v9 2/7] i2c: Add FSI-attached I2C master algorithm

On Mon, 2018-06-04 at 22:21 +0300, Andy Shevchenko wrote:
> > +#define I2C_INT_ENABLE         0x0000ff80
> > +#define I2C_INT_ERR            0x0000fcc0
> 
> Now it looks like a flags combinations.
> For me as for reader would be better to see quickly a decoded line.
> 
> My proposal is to introduce something like following
> 
> _INT_ALL  GENMASK()
> _INT_ENABLE (_INT_ALL & ~(_FOO | _BAR))
> _INT_ERR ... similar way as above ...
> 
> What do you think?

I don't think this absolutely needs to change but yes, open coding is
error prone. However I would think it more readable to use positive
logic and just list all the bits that are *set* even if it's a bit more
text:

#define I2C_INT_ERR	(I2C_INT_INV_CMD	|\                			
 I2C_INT_PARITY         |\
			 I2C_INT_BE_OVERRUN	|\
			.../...)

#define I2C_INT_ENABLE	(I2C_INT_ERR		|\
			 I2C_INT_DAT_REQ	|\
			 I2C_INT_CMD_COMP)

Note: Eddie, I notice I2C_INT_BUSY is in "ERR" but not in "ENABLE", any
reason for that ?

Cheers,
Ben.