[dpdk-dev] [RFC PATCH 1/6] eal: introduce macros for getting value for bit

Parav Pandit parav at mellanox.com
Thu Jun 18 14:16:15 CEST 2020


Hi Thomas,

> From: dev <dev-bounces at dpdk.org> On Behalf Of Parav Pandit
> Sent: Thursday, June 18, 2020 2:55 PM
> 
> > From: Thomas Monjalon <thomas at monjalon.net>
> > Sent: Wednesday, June 17, 2020 1:35 PM
> >
> > 15/06/2020 21:33, Gaëtan Rivet:
> > > On 10/06/20 17:17 +0000, Parav Pandit wrote:
> > > > There are several drivers which duplicate bit generation macro.
> > > > Introduce a generic bit macros so that such drivers avoid
> > > > redefining same in multiple drivers.
> > > >
> > > > Signed-off-by: Parav Pandit <parav at mellanox.com>
> > > > ---
> > [...]
> > > > --- /dev/null
> > > > +++ b/lib/librte_eal/include/rte_bits.h
> > > > @@ -0,0 +1,10 @@
> > > > +/* SPDX-License-Identifier: BSD-3-Clause
> > > > + * Copyright 2020 Mellanox Technologies, Ltd.
> > > > + */
> > > > +
> > > > +#ifndef _RTE_BITS_H_
> > > > +#define _RTE_BITS_H_
> > > > +
> > > > +#define RTE_BIT(bit_num)	(1UL << (bit_num))
> > >                            ^ The tab here should be replaced by a space.
> > > > +
> > > > +#endif
> > >
> > > I'm not sure this kind of macro is needed, but if multiple drivers
> > > are using the patterns let's say ok.
> > >
> Yes. we certainly need it. Currently BIT() macro is used at 3000+ locations and
> defined in 10+ drivers.
> Once we have this macro, it can gradually be replaced.
> 
> > > However I don't think it needs its own header. Would it be ok in
> > > lib/librte_eal/include/rte_common.h for example?
> >
> > If we want to reuse an existing file, it could be
> > lib/librte_eal/include/rte_bitops.h
> >
> o.k.
> I will rename file from rte_bits.h to rte_bitops.h More such macros will be
> available here to avoid redefinitions in drivers.

I see that rte_bitops.h already exist and this new definition doesn't fit well in the rte_bitops.h.
The intent of the rte_bitops.h is to have generic mostly macros to replace current duplication of:

Such as
BIT()
BIT_ULL()
BITS_PER_BYTE()
BITS_TO_LONGS()

They do not fit well in rte_bitops.h which works on the 'bitmap'.


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