Message-ID: <1430858413.16357.252.camel@freescale.com>
Subject: Re: [PATCH 1/7] staging: fsl-mc: MC bus IRQ support
From: Scott Wood <scottwood@freescale.com>
To: Rivera Jose-B46482 <German.Rivera@freescale.com>
CC: Dan Carpenter <dan.carpenter@oracle.com>,
        "devel@driverdev.osuosl.org" <devel@driverdev.osuosl.org>,
        Yoder Stuart-B08248 <stuart.yoder@freescale.com>,
        Hamciuc Bogdan-BHAMCIU1 <bhamciu1@freescale.com>,
        "arnd@arndb.de" <arnd@arndb.de>,
        "Sharma Bhupesh-B45370" <bhupesh.sharma@freescale.com>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "agraf@suse.de" <agraf@suse.de>,
        "Erez Nir-RM30794" <nir.erez@freescale.com>,
        katz Itai-RM05202 <itai.katz@freescale.com>,
        Marginean Alexandru-R89243 <R89243@freescale.com>,
        Schmitt Richard-B43082 <richard.schmitt@freescale.com>
Date: Tue, 5 May 2015 15:40:13 -0500
In-Reply-To: <DM2PR0301MB13095252BF220671E3BF42AEFED10@DM2PR0301MB1309.namprd03.prod.outlook.com>
References: <1430242750-17745-1-git-send-email-German.Rivera@freescale.com>
	 <1430242750-17745-2-git-send-email-German.Rivera@freescale.com>
	 <20150430114957.GW14154@mwanda>
	 <DM2PR0301MB1309AA660970101D3882E650FED20@DM2PR0301MB1309.namprd03.prod.outlook.com>
	 <20150505084830.GL16501@mwanda>
	 <DM2PR0301MB1309A6F411B54A6A1626E78EFED10@DM2PR0301MB1309.namprd03.prod.outlook.com>
	 <20150505164011.GT14154@mwanda> <1430855801.16357.251.camel@freescale.com>
	 <DM2PR0301MB13095252BF220671E3BF42AEFED10@DM2PR0301MB1309.namprd03.prod.outlook.com>
Content-Type: text/plain; charset="UTF-8"
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 05 May 2015 20:40:21.3874
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY1PR03MB1482
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org
Content-Length: 3542
Lines: 77

On Tue, 2015-05-05 at 15:22 -0500, Rivera Jose-B46482 wrote:
> 
> 
> > -----Original Message-----
> > From: Wood Scott-B07421
> > Sent: Tuesday, May 05, 2015 2:57 PM
> > To: Dan Carpenter
> > Cc: Rivera Jose-B46482; devel@driverdev.osuosl.org; Yoder Stuart-B08248;
> > Hamciuc Bogdan-BHAMCIU1; arnd@arndb.de; Sharma Bhupesh-B45370;
> > gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org; agraf@suse.de;
> > Erez Nir-RM30794; katz Itai-RM05202; Marginean Alexandru-R89243; Schmitt
> > Richard-B43082
> > Subject: Re: [PATCH 1/7] staging: fsl-mc: MC bus IRQ support
> > 
> > On Tue, 2015-05-05 at 19:40 +0300, Dan Carpenter wrote:
> > > On Tue, May 05, 2015 at 04:08:49PM +0000, Jose Rivera wrote:
> > > > > Subject: Re: [PATCH 1/7] staging: fsl-mc: MC bus IRQ support
> > > > >
> > > > > On Mon, May 04, 2015 at 10:09:08PM +0000, Jose Rivera wrote:
> > > > > > > > +		WARN_ON((int16_t)irq_count < 0);
> > > > > > >
> > > > > > > This code is doing "WARN_ON(test_bit(15, (unsigned long
> > > > > *)&irq_count));".
> > > > > > > That seems like nonsense.  Anyway, just delete the WARN_ON().
> > > > > > >
> > > > > > I disagree. This WARN_ON is checking that irq_count is in the
> > > > > > expected range (it fits in int16_t as a positive number). The
> > > > > > dprc_scan_objects() function expects irq_count to be of type
> > > > > > "unsigned int" (which is 32-bit unsigned)
> > > > > >
> > > > >
> > > > > You're not allowed to disagree because it's a testable thing and
> > > > > not an opinion about style or something.  :P  What you want is:
> > > > >
> > > > > 	WARN_ON(irq_count > SHRT_MAX);
> > > > >
> > > > I see your point now. The check "(int16_t)irq_count < 0)" will not
> > > > be able to catch 0x10000 > 0x7fff, but "irq_count > SHRT_MAX) will.
> > > > So I'll make the suggested change, but I would prefer to use S16_MAX
> > > > rather than SHRT_MAX.
> > > >
> > >
> > > Huh?  I didn't even know about the S16_MAX definition.  There are
> > > literally no users of it in the kernel.  It's not very fair because
> > > there are few users of SHRT_MAX.  But there are literally no users of
> > > S32_MAX in the kernel and 358 users of INT_MAX.
> > >
> > > Don't insist that you must be special and different from everyone else.
> > 
> > There are some users of U16_MAX, U32_MAX, and U64_MAX.  Why use a limit
> > for a different type than is being used?  Why have s16/s32 at all if
> > you're going to conflate it with short/int elsewhere?
> > 
> > That said, I don't see where this code is actually using s16 (or
> > int16_t) for irq_count except in these weird error checks.  German, why
> > do you need to check against 0x7fff (whatever you call it) at all?
> > Won't comparing to a promoted-to-unsigned-int .max_count (as you do
> > immediately after the WARN_ON) suffice?
> > 
> mc_bus->resource_pools[FSL_MC_POOL_IRQ].max_count is of type int16_t
> (and is so, because its value comes from an MC API that returns
> an int16_t). The reason for checking irq_count against 0x7ffff is to 
> catch the case in which irq_count is out of range (irq_count originates
> from values coming from the MC device, so we should do some validation
> before using it)

Comparing irq_count with max_count will catch any condition that
comparing irq_count with 0x7fff will catch.

-Scott


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/