Subject: Re: [net] i40e: _MASK vs _SHIFT typo in i40e_handle_mdd_event()

From: Joe Perches <[email-masked]>
Date: Wed, 22 Oct 2014 21:05:07 -0700

On Wed, 2014-10-22 at 20:22 -0700, Joe Perches wrote:
> On Wed, 2014-10-22 at 20:06 -0700, Jeff Kirsher wrote:
> > We accidentally mask by the _SHIFT variable.  It means that "event" is
> > always zero.
> []
> > diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
> []
> > @@ -6151,7 +6151,7 @@ static void i40e_handle_mdd_event(struct i40e_pf *pf)
> >  				I40E_GL_MDET_TX_PF_NUM_SHIFT;
> >  		u8 vf_num = (reg & I40E_GL_MDET_TX_VF_NUM_MASK) >>
> >  				I40E_GL_MDET_TX_VF_NUM_SHIFT;
> > -		u8 event = (reg & I40E_GL_MDET_TX_EVENT_SHIFT) >>
> > +		u8 event = (reg & I40E_GL_MDET_TX_EVENT_MASK) >>
> >  				I40E_GL_MDET_TX_EVENT_SHIFT;
> >  		u8 queue = (reg & I40E_GL_MDET_TX_QUEUE_MASK) >>
> >  				I40E_GL_MDET_TX_QUEUE_SHIFT;
> > @@ -6165,7 +6165,7 @@ static void i40e_handle_mdd_event(struct i40e_pf *pf)
> >  	if (reg & I40E_GL_MDET_RX_VALID_MASK) {
> >  		u8 func = (reg & I40E_GL_MDET_RX_FUNCTION_MASK) >>
> >  				I40E_GL_MDET_RX_FUNCTION_SHIFT;
> > -		u8 event = (reg & I40E_GL_MDET_RX_EVENT_SHIFT) >>
> > +		u8 event = (reg & I40E_GL_MDET_RX_EVENT_MASK) >>
> >  				I40E_GL_MDET_RX_EVENT_SHIFT;
> >  		u8 queue = (reg & I40E_GL_MDET_RX_QUEUE_MASK) >>
> >  				I40E_GL_MDET_RX_QUEUE_SHIFT;
> 
> It might be useful to have a macro for that.
> Something like:
> 
> #define GET_REG_VAL(reg, type)			\
> 	((reg & type##_MASK) >> type##_SHIFT)
> 
> so these could become:
> 
> 	u8 vf_num = GET_REG_VAL(reg, I40E_GL_MDET_TX_VF_NUM);
> 	u8 event = GET_REG_VAL(reg, I40E_GL_MDET_TX_EVENT);
> 
> etc...

btw:  Here's a defect:

Using the macro would also prevent this sort of precedence defect

diff --git a/drivers/net/ethernet/intel/i40e/i40e_common.c b/drivers/net/ethernet/intel/i40e/i40e_common.c
[]
@@ -809,8 +809,8 @@ i40e_status i40e_pf_reset(struct i40e_hw *hw)
         * The grst delay value is in 100ms units, and we'll wait a
         * couple counts longer to be sure we don't just miss the end.
         */
-       grst_del = rd32(hw, I40E_GLGEN_RSTCTL) & I40E_GLGEN_RSTCTL_GRSTDEL_MASK
-                       >> I40E_GLGEN_RSTCTL_GRSTDEL_SHIFT;

bit shift has higher precedence than bitwise &