linux-kernel - Re: [PATCH v2 05/15] spi: Remove code duplication in spi_add_device

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20230711120133.45drgk46y4cz7aut@mercury.elektranox.org>
Date:   Tue, 11 Jul 2023 14:01:33 +0200
From:   Sebastian Reichel <sebastian.reichel@...labora.com>
To:     Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc:     Mark Brown <broonie@...nel.org>,
        Cristian Ciocaltea <cristian.ciocaltea@...labora.com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Amit Kumar Mahapatra via Alsa-devel 
        <alsa-devel@...a-project.org>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Tharun Kumar P <tharunkumar.pasumarthi@...rochip.com>,
        Vijaya Krishna Nivarthi <quic_vnivarth@...cinc.com>,
        Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>, linux-spi@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-amlogic@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org, linux-arm-msm@...r.kernel.org,
        linux-rockchip@...ts.infradead.org,
        linux-riscv@...ts.infradead.org,
        linux-stm32@...md-mailman.stormreply.com,
        linux-trace-kernel@...r.kernel.org, netdev@...r.kernel.org,
        Sanjay R Mehta <sanju.mehta@....com>,
        Radu Pirea <radu_nicolae.pirea@....ro>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Tudor Ambarus <tudor.ambarus@...aro.org>,
        Serge Semin <fancer.lancer@...il.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        Kevin Hilman <khilman@...libre.com>,
        Jerome Brunet <jbrunet@...libre.com>,
        Martin Blumenstingl <martin.blumenstingl@...glemail.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Heiko Stuebner <heiko@...ech.de>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Alain Volmat <alain.volmat@...s.st.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...s.st.com>,
        Max Filippov <jcmvbkbc@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH v2 05/15] spi: Remove code duplication in
 spi_add_device_locked()

Hi,

On Tue, Jul 11, 2023 at 02:06:20PM +0300, Andy Shevchenko wrote:
> On Mon, Jul 10, 2023 at 06:16:22PM +0100, Mark Brown wrote:
> > On Mon, Jul 10, 2023 at 06:49:22PM +0300, Andy Shevchenko wrote:
> > > Seems by unknown reason, probably some kind of mis-rebase,
> > > the commit 0c79378c0199 ("spi: add ancillary device support")
> > > adds a dozen of duplicating lines of code. Drop them.
> > > 
> > > Signed-off-by: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
> > > ---
> > >  drivers/spi/spi.c | 11 -----------
> > >  1 file changed, 11 deletions(-)
> > > 
> > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c
> > > index c99ee4164f11..46cbda383228 100644
> > > --- a/drivers/spi/spi.c
> > > +++ b/drivers/spi/spi.c
> > > @@ -712,17 +712,6 @@ EXPORT_SYMBOL_GPL(spi_add_device);
> > >  static int spi_add_device_locked(struct spi_device *spi)
> > >  {
> > >  	struct spi_controller *ctlr = spi->controller;
> > > -	struct device *dev = ctlr->dev.parent;
> > > -
> > > -	/* Chipselects are numbered 0..max; validate. */
> > > -	if (spi_get_chipselect(spi, 0) >= ctlr->num_chipselect) {
> > > -		dev_err(dev, "cs%d >= max %d\n", spi_get_chipselect(spi, 0),
> > > -			ctlr->num_chipselect);
> > > -		return -EINVAL;
> > > -	}
> > > -
> > > -	/* Set the bus ID string */
> > > -	spi_dev_set_name(spi);
> > 
> > I see that this is duplicating spi_add_device() (and we really could do
> > better with code sharing there I think) but I can't immediately see
> > where the duplication that's intended to be elimiated is here - where
> > else in the one call path that spi_add_device_locked() has would we do
> > the above?  Based on the changelog I was expecting to see some
> > duplicated code in the function itself.
> 
> Oh, by some reason Sebastian wasn't in this rather long Cc list.
> Added him.
> 
> Reading again I don't see any useful explanation why that piece of code has to
> be duplicated among these two functions. It's 100% a copy.
> 
> Sebastian, can you shed some light here?

The patch in this thread is obviously wrong. It results in the
checks never beeing called for spi_add_device_locked(). The copy is
in spi_add_device() and those two are not calling into each other.

But it should be fine to move the code to the start of
__spi_add_device(), which allows removing the duplication. In that
case the code will be run with the add_lock held, which is probably
what I was worried about two years ago. Looking at it again, the
lock is held anyways in case of spi_add_device_locked().

Greetings,

-- Sebastian

Download attachment "signature.asc" of type "application/pgp-signature" (834 bytes)