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

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Message-ID: <ZK1PfXsUJipjcCH6@smile.fi.intel.com>
Date:   Tue, 11 Jul 2023 15:47:57 +0300
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Sebastian Reichel <sebastian.reichel@...labora.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,
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        Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH v2 05/15] spi: Remove code duplication in
 spi_add_device_locked()

On Tue, Jul 11, 2023 at 02:01:33PM +0200, Sebastian Reichel wrote:
> 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:

...

> > > > -	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.

Ah, now I see, I missed __ in the name.
Thank you for opening my eyes!

> 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().

Right, I will re-do that.

-- 
With Best Regards,
Andy Shevchenko