All of lore.kernel.org
 help / color / mirror / Atom feed
From: Richard Cochran <richardcochran@gmail.com>
To: David Laight <David.Laight@ACULAB.COM>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	Jeff Kirsher <jeffrey.t.kirsher@intel.com>,
	John Stultz <john.stultz@linaro.org>,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH net-next 1/7] timecounter: provide a macro to initialize the cyclecounter mask field.
Date: Mon, 5 Jan 2015 14:43:27 +0100	[thread overview]
Message-ID: <20150105134327.GA8156@localhost.localdomain> (raw)
In-Reply-To: <063D6719AE5E284EB5DD2968C1650D6D1CAC09D7@AcuExch.aculab.com>

On Mon, Jan 05, 2015 at 01:20:57PM +0000, David Laight wrote:
> > +/* simplify initialization of mask field */
> > +#define CYCLECOUNTER_MASK(bits) (cycle_t)((bits) < 64 ? ((1ULL<<(bits))-1) : -1)
> 
> That has me chasing through the C integer promotion rules.
> Better might be:
> 	((bits) < 64 ? (1ULL << (bits)) - 1 : (((1ULL << 63) - 1) << 1) + 1)
> I actually suspect there is a standard definition somewhere?

This is an exact copy of CLOCKSOURCE_MASK, and if wrong, then both are
wrong.  In any case, I can't see any issue here. Is not

	(some_int_type) -1

always equal to

	0xf...(width of type)

for all integer types, when using 2s compliment?

Thanks
Richard





  reply	other threads:[~2015-01-05 13:43 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-31 23:33 [PATCH 1/2] e1000e: Include clocksource.h to get CLOCKSOURCE_MASK David Miller
2014-12-31 23:42 ` Jeff Kirsher
2015-01-01 10:39 ` [PATCH net-next 0/7] Fixing the "Time Counter fixes and improvements" Richard Cochran
2015-01-01 10:39   ` [PATCH net-next 1/7] timecounter: provide a macro to initialize the cyclecounter mask field Richard Cochran
2015-01-05 13:20     ` David Laight
2015-01-05 13:43       ` Richard Cochran [this message]
2015-01-05 13:53         ` David Laight
2015-01-01 10:39   ` [PATCH net-next 2/7] bnx2x: convert to CYCLECOUNTER_MASK macro Richard Cochran
2015-01-01 10:39   ` [PATCH net-next 3/7] e1000e: " Richard Cochran
2015-01-01 10:39   ` [PATCH net-next 4/7] igb: " Richard Cochran
2015-01-01 10:39   ` [PATCH net-next 5/7] ixgbe: " Richard Cochran
2015-01-01 10:40   ` [PATCH net-next 6/7] mlx4: include clocksource.h again Richard Cochran
2015-01-01 10:40   ` [PATCH net-next 7/7] microblaze: include the new timecounter header Richard Cochran
2015-01-02 19:22 ` [PATCH net-next V2 0/7] Fixing the "Time Counter fixes and improvements" Richard Cochran
2015-01-02 19:22   ` [PATCH net-next V2 1/7] timecounter: provide a macro to initialize the cyclecounter mask field Richard Cochran
2015-01-02 19:22   ` [PATCH net-next V2 2/7] bnx2x: convert to CYCLECOUNTER_MASK macro Richard Cochran
2015-01-02 19:22   ` [PATCH net-next V2 3/7] e1000e: " Richard Cochran
2015-01-02 19:22   ` [PATCH net-next V2 4/7] igb: " Richard Cochran
2015-01-02 19:22   ` [PATCH net-next V2 5/7] ixgbe: " Richard Cochran
2015-01-02 19:22   ` [PATCH net-next V2 6/7] mlx4: include clocksource.h again Richard Cochran
2015-01-02 19:22   ` [PATCH net-next V2 7/7] microblaze: include the new timecounter header Richard Cochran
2015-01-02 21:48   ` [PATCH net-next V2 0/7] Fixing the "Time Counter fixes and improvements" David Miller

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20150105134327.GA8156@localhost.localdomain \
    --to=richardcochran@gmail.com \
    --cc=David.Laight@ACULAB.COM \
    --cc=davem@davemloft.net \
    --cc=jeffrey.t.kirsher@intel.com \
    --cc=john.stultz@linaro.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=netdev@vger.kernel.org \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.