On 2019-04-18 01:48, Ray Jui wrote: > > > On 4/14/2019 11:56 PM, Peter Rosin wrote: >> On 2019-04-13 00:59, Peter Rosin wrote: >>> On 2019-04-03 23:05, Ray Jui wrote: >>>> Change the iProc I2C driver to use the 'BIT' macro from all '1 << XXX' >>>> bit operations to get rid of compiler warning and improve readability of >>>> the code >>> >>> All? I see lots more '1 << XXX_SHIFT' matches. I might be behind though? >> >> I verified that, and yes indeed, I was behind. That said, see below... >> > > Right. Previous change that this change depends on is already queued in > i2c/for-next. > >>> Anyway, if you are cleaning up, I'm just flagging that BIT(XXX_SHIFT) looks >>> a bit clunky to me. You might consider renaming all those single-bit >>> XXX_SHIFT macros to simple be >>> >>> #define XXX BIT(<xxx>) >>> >>> instead of >>> >>> #define XXX_SHIFT <xxx> >>> >>> but that triggers more churn, so is obviously more error prone. You might >>> not dare it? >>> > > With the current code, I don't see how that is cleaner. With XXX_SHIFT > specified, it makes it very clear to the user that the define a for a > bit location within a register. You can argue and say it makes the > define longer, but not less clear. > >>> Cheers, >>> Peter >>> >>>> Signed-off-by: Ray Jui <ray....@broadcom.com> >>>> --- >>>> drivers/i2c/busses/i2c-bcm-iproc.c | 6 +++--- >>>> 1 file changed, 3 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c >>>> b/drivers/i2c/busses/i2c-bcm-iproc.c >>>> index 562942d0c05c..a845b8decac8 100644 >>>> --- a/drivers/i2c/busses/i2c-bcm-iproc.c >>>> +++ b/drivers/i2c/busses/i2c-bcm-iproc.c >>>> @@ -717,7 +717,7 @@ static int bcm_iproc_i2c_xfer_single_msg(struct >>>> bcm_iproc_i2c_dev *iproc_i2c, >>>> >>>> /* mark the last byte */ >>>> if (i == msg->len - 1) >>>> - val |= 1 << M_TX_WR_STATUS_SHIFT; >>>> + val |= BIT(M_TX_WR_STATUS_SHIFT); >>>> >>>> iproc_i2c_wr_reg(iproc_i2c, M_TX_OFFSET, val); >>>> } >>>> @@ -844,7 +844,7 @@ static int bcm_iproc_i2c_cfg_speed(struct >>>> bcm_iproc_i2c_dev *iproc_i2c) >>>> >>>> iproc_i2c->bus_speed = bus_speed; >>>> val = iproc_i2c_rd_reg(iproc_i2c, TIM_CFG_OFFSET); >>>> - val &= ~(1 << TIM_CFG_MODE_400_SHIFT); >>>> + val &= ~BIT(TIM_CFG_MODE_400_SHIFT); >>>> val |= (bus_speed == 400000) << TIM_CFG_MODE_400_SHIFT; >> >> These two statements now no longer "match". One uses BIT and the other open >> codes the shift. I think that's bad. Losing the _SHIFT suffix and including >> BIT in the macro expansion, as suggested above, yields: >> >> val &= ~TIM_CFG_MODE_400; >> if (bus_speed == 400000) >> val |= TIM_CFG_MODE_400; >> >> which is perhaps one more line, but also more readable IMO. >> > > A single line with evaluation embedded is nice and clean to me. I guess > this is subjective.
The "problem" I had when I looked at the driver was not any one specific instance. It was just that, for my taste, the code had too many shifts etc inline with the real code. Replacing 1 << xyz_SHIFT with BIT(xyz_SHIFT) is not a real improvement, they are just about equal to me, it's just that there are still too many mechanical things happening that could easily be tucked away with the suggested approach. > I'll leave the decision to Wolfram. If he also prefers the above change > to be made, sure. Otherwise, I'll leave it as it is. But if you see no value in my suggestion and/or don't what to take the cleanup one step further, then just leave it as-is. >> But all this is of course in deep nit-pick-territory... >> >> Cheers, >> Peter >> > > Thanks, > > Ray >
