netdev - RE: [PATCH v10 03/20] dlb: add resource and device initialization

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Date:   Wed, 10 Mar 2021 20:26:02 +0000
From:   "Chen, Mike Ximing" <mike.ximing.chen@...el.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.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 v10 03/20] dlb: add resource and device initialization


> -----Original Message-----
> From: Greg KH <gregkh@...uxfoundation.org>
> Sent: Wednesday, March 10, 2021 3:13 AM
> To: Chen, Mike Ximing <mike.ximing.chen@...el.com>
> Cc: netdev@...r.kernel.org; davem@...emloft.net; kuba@...nel.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 v10 03/20] dlb: add resource and device initialization
> 
> On Wed, Mar 10, 2021 at 01:33:24AM +0000, Chen, Mike Ximing wrote:
> >
> > > -----Original Message-----
> > > From: Greg KH <gregkh@...uxfoundation.org>
> > >
> > > On Wed, Feb 10, 2021 at 11:54:06AM -0600, Mike Ximing Chen wrote:
> > > > +
> > > > +#include "dlb_bitmap.h"
> > > > +
> > > > +#define BITS_SET(x, val, mask)	(x = ((x) & ~(mask))     \
> > > > +				 | (((val) << (mask##_LOC)) & (mask)))
> > > > +#define BITS_GET(x, mask)       (((x) & (mask)) >> (mask##_LOC))
> > >
> > > Why not use the built-in kernel functions for this?  Why are you
> > > creating your own?
> > >
> > 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 keep them?
> 
> No, please use the kernel-wide proper functions, there's no need for
> single tiny driver to be "special" in this regard.  If somehow the
> in-kernel functions are not sufficient, it's always better to fix them
> up than to go your own way here.
> 

OK. I will use FIELD_GET() and FIELD_PREP() macros in the next revision.

Thanks
Mike