> -----Original Message----- > From: Andy Shevchenko <andy.shevchenko@xxxxxxxxx> > Sent: Tuesday, September 20, 2022 3:39 PM > To: Sa, Nuno <Nuno.Sa@xxxxxxxxxx> > Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx; linux-rockchip@xxxxxxxxxxxxxxxxxxx; > linux-amlogic@xxxxxxxxxxxxxxxxxxx; linux-imx@xxxxxxx; linux- > iio@xxxxxxxxxxxxxxx; Chunyan Zhang <zhang.lyra@xxxxxxxxx>; Hennerich, > Michael <Michael.Hennerich@xxxxxxxxxx>; Martin Blumenstingl > <martin.blumenstingl@xxxxxxxxxxxxxx>; Sascha Hauer > <s.hauer@xxxxxxxxxxxxxx>; Cixi Geng <cixi.geng1@xxxxxxxxxx>; Kevin > Hilman <khilman@xxxxxxxxxxxx>; Vladimir Zapolskiy <vz@xxxxxxxxx>; > Pengutronix Kernel Team <kernel@xxxxxxxxxxxxxx>; Alexandru Ardelean > <aardelean@xxxxxxxxxxx>; Fabio Estevam <festevam@xxxxxxxxx>; Andriy > Tryshnivskyy <andriy.tryshnivskyy@xxxxxxxxxxxxxxx>; Haibo Chen > <haibo.chen@xxxxxxx>; Shawn Guo <shawnguo@xxxxxxxxxx>; Hans de > Goede <hdegoede@xxxxxxxxxx>; Miquel Raynal > <miquel.raynal@xxxxxxxxxxx>; Jerome Brunet <jbrunet@xxxxxxxxxxxx>; > Heiko Stuebner <heiko@xxxxxxxxx>; Florian Boor > <florian.boor@xxxxxxxxxxxxxxxxx>; Regus, Ciprian > <Ciprian.Regus@xxxxxxxxxx>; Lars-Peter Clausen <lars@xxxxxxxxxx>; > Jonathan Cameron <jic23@xxxxxxxxxx>; Neil Armstrong > <narmstrong@xxxxxxxxxxxx>; Baolin Wang > <baolin.wang@xxxxxxxxxxxxxxxxx>; Jyoti Bhayana <jbhayana@xxxxxxxxxx>; > Chen-Yu Tsai <wens@xxxxxxxx>; Orson Zhai <orsonzhai@xxxxxxxxx> > Subject: Re: [PATCH 03/15] iio: adc: axp288_adc: do not use internal iio_dev > lock > > [External] > > On Tue, Sep 20, 2022 at 4:37 PM Andy Shevchenko > <andy.shevchenko@xxxxxxxxx> wrote: > > On Tue, Sep 20, 2022 at 4:18 PM Sa, Nuno <Nuno.Sa@xxxxxxxxxx> wrote: > > > > On Tue, Sep 20, 2022 at 2:28 PM Nuno Sá <nuno.sa@xxxxxxxxxx> > wrote: > > ... > > > > > > info = iio_priv(indio_dev); > > > > > + mutex_init(&info->lock); > > > > > info->irq = platform_get_irq(pdev, 0); > > > > > if (info->irq < 0) > > > > > return info->irq; > > > > > > > > Consider initializing it as late as possible, like after IRQ retrieval > > > > in this context (maybe even deeper, but no context available). Ditto > > > > for the rest of the series. > > > > > > Any special reason for it (maybe related to lockdep :wondering: ) ? Just > > > curious as I never noticed such a pattern when initializing mutexes. > > > > Yes. Micro-optimization based on the rule "don't create a resource in > > case of known error". > > > > OTOH, you have to be sure that the mutex (and generally speaking a > > locking) should be initialized early enough. > Typically not really needed during probe... > Note that "micro" in the above can be multiplied by 'k', where 'k' is > the amount of deferred probes (probably not the case here, but again, > "generally speaking"). > Well, I don't think 'mutex_init()' does that much that really matters in these patches but ok, that rule is indeed a good practice that sometimes makes a difference. And since I will definitely need a v2, I can make that change. Where applicable, the best place is probably before registering the IIO device... - Nuno Sá
