Re: [PATCH 3/8] i2c: omap: fix error checking

[Felipe Balbi]

Hi,

On Thu, Oct 25, 2012 at 12:33:18PM +0200, Michael Trimarchi wrote:
> >>> @@ -587,9 +587,9 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap,
> >>>           goto err_i2c_init;
> >>>   }
> >>>  
> >>> - /* We have an error */
> >>> - if (dev->cmd_err & (OMAP_I2C_STAT_AL | OMAP_I2C_STAT_ROVR |
> >>> -                     OMAP_I2C_STAT_XUDF)) {
> >>> + if ((dev->cmd_err & OMAP_I2C_STAT_AL)
> >>> +                 || (dev->cmd_err & OMAP_I2C_STAT_ROVR)
> >>> +                 || (dev->cmd_err & OMAP_I2C_STAT_XUDF)) {
> >>
> >> Sorry, what is the difference? I didn't understand the optimisation
> >> and why now is more clear. Can you just add a comment?
> > 
> > semantically they're not the same, right ? We want to check if each of
> > those bits are set, not if all of them are set together.
> > 
> > my 2 cents.
> 
> You are doing the same thing, but of course is better with just one

I never claimed the contrary. I said *semantically* they're not the
same.

> *if* as before . A general rule is: when you have logic expression you

We still have a single *if* and I'm sure compiler will optimize that
expression as much as it likes.

> can use undefined states to simplify the logic. 

don't-care is not the same as undefined states.

-- 
balbi

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