linux-kernel - RE: [PATCH v8 03/20] dlb: add resource and device initialization

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Date:   Sun, 10 Jan 2021 17:22:32 +0000
From:   "Chen, Mike Ximing" <mike.ximing.chen@...el.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "pierre-louis.bossart@...ux.intel.com" 
        <pierre-louis.bossart@...ux.intel.com>
Subject: RE: [PATCH v8 03/20] dlb: add resource and device initialization



> -----Original Message-----
> From: Greg KH <gregkh@...uxfoundation.org>
> Sent: Thursday, January 7, 2021 2:40 PM
> To: Chen, Mike Ximing <mike.ximing.chen@...el.com>
> Cc: linux-kernel@...r.kernel.org; arnd@...db.de; Williams, Dan J
> <dan.j.williams@...el.com>; pierre-louis.bossart@...ux.intel.com; Gage Eads
> <gage.eads@...el.com>
> Subject: Re: [PATCH v8 03/20] dlb: add resource and device initialization
> 
> On Mon, Jan 04, 2021 at 08:58:22PM -0600, Mike Ximing Chen wrote:
> > Introduce dlb_bitmap_* functions, a thin convenience layer wrapping the
> > Linux bitmap interfaces, used by the bitmaps in the dlb hardware types.
> 
> No, you created custom #defines:
> 
> > --- a/drivers/misc/dlb/dlb_hw_types.h
> > +++ b/drivers/misc/dlb/dlb_hw_types.h
> > @@ -5,6 +5,15 @@
> >  #define __DLB_HW_TYPES_H
> >
> >  #include <linux/io.h>
> > +#include <linux/types.h>
> > +
> > +#include "dlb_bitmap.h"
> > +
> > +#define BITS_SET(x, val, mask)	(x = ((x) & ~(mask))     \
> > +				 | (((val) << (mask##_LOC)) & (mask)))
> > +#define BITS_CLR(x, mask)	((x) &= ~(mask))
> > +#define BIT_SET(x, mask)        ((x) |= (mask))
> > +#define BITS_GET(x, mask)       (((x) & (mask)) >> (mask##_LOC))
> 
> We have functions for this, use them, don't create custom macros for
> them.  Use the Linux functions please.
> 
> thanks,
> 
> greg k-h

FIELD_GET(_mask, _val) and FIELD_PREP(_mask, _val) in include/linux/bitfield.h are similar to our BITS_GET() and BITS_SET().  However in our case, mask##_LOC is a known constant defined in dlb_regs.h.  So we don't need to use _buildin_ffs(mask) to calculate the location of mask as FIELD_GET() and FIELD_PREP() do.  We can still use FIELD_GET and FIELD_PREP, but our macros are a little more efficient. Would it be OK to use them? 

Thanks
Mike