Re: [PATCH 01/18] i2c: guarantee that I2C_M_RD will be 0x0001 forever

["Shevchenko, Andriy" <andriy.shevchenko@intel.com>]

On Mon, 2016-04-04 at 13:26 +0300, Andy Shevchenko wrote:
> On Sun, 2016-04-03 at 20:44 +0200, Wolfram Sang wrote:
> > 
> > There is code out there in user space and kernel space which relies
> > on
> > I2C_M_RD being bit 0 to simplify their bit operations. Add a
> > comment
> > to
> > make sure this will never break. Do proper sorting of the defines
> > while
> > we are here.
> Didn't see a comment as stated though.

Ah, overlooked it. Anyway, perhaps worth to mention under
Documentation. What do you think?

> 
> > 
> > 
> > Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
> > ---
> >  include/uapi/linux/i2c.h | 13 +++++++------
> >  1 file changed, 7 insertions(+), 6 deletions(-)
> > 
> > diff --git a/include/uapi/linux/i2c.h b/include/uapi/linux/i2c.h
> > index b0a7dd61eb353a..adcbef4bff610a 100644
> > --- a/include/uapi/linux/i2c.h
> > +++ b/include/uapi/linux/i2c.h
> > @@ -68,14 +68,15 @@
> >  struct i2c_msg {
> >  	__u16 addr;	/* slave address			
> > *
> > /
> >  	__u16 flags;
> > -#define I2C_M_TEN		0x0010	/* this is a ten
> > bit
> > chip address */
> >  #define I2C_M_RD		0x0001	/* read data, from
> > slave to master */
> > -#define I2C_M_STOP		0x8000	/* if
> > I2C_FUNC_PROTOCOL_MANGLING */
> > -#define I2C_M_NOSTART		0x4000	/* if
> > I2C_FUNC_NOSTART */
> > -#define I2C_M_REV_DIR_ADDR	0x2000	/* if
> > I2C_FUNC_PROTOCOL_MANGLING */
> > -#define I2C_M_IGNORE_NAK	0x1000	/* if
> > I2C_FUNC_PROTOCOL_MANGLING */
> > -#define I2C_M_NO_RD_ACK		0x0800	/* if
> > I2C_FUNC_PROTOCOL_MANGLING */
> > +					/* I2C_M_RD is guaranteed
> > to
> > be 0x0001! */
> > +#define I2C_M_TEN		0x0010	/* this is a ten
> > bit
> > chip address */
> >  #define I2C_M_RECV_LEN		0x0400	/* length will
> > be first received byte */
> > +#define I2C_M_NO_RD_ACK		0x0800	/* if
> > I2C_FUNC_PROTOCOL_MANGLING */
> > +#define I2C_M_IGNORE_NAK	0x1000	/* if
> > I2C_FUNC_PROTOCOL_MANGLING */
> > +#define I2C_M_REV_DIR_ADDR	0x2000	/* if
> > I2C_FUNC_PROTOCOL_MANGLING */
> > +#define I2C_M_NOSTART		0x4000	/* if
> > I2C_FUNC_NOSTART */
> > +#define I2C_M_STOP		0x8000	/* if
> > I2C_FUNC_PROTOCOL_MANGLING */
> >  	__u16 len;		/* msg length			
> > 	*/
> >  	__u8 *buf;		/* pointer to msg data		
> > 	*/
> >  };

-- 
Andy Shevchenko <andriy.shevchenko@intel.com>
Intel Finland Oy
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