linux-kernel - RE: [PATCH v2 7/8] iio: core: simplify alloc alignment code

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Date:   Fri, 15 May 2020 07:12:40 +0000
From:   "Sa, Nuno" <Nuno.Sa@...log.com>
To:     "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "ludovic.desroches@...rochip.com" <ludovic.desroches@...rochip.com>,
        "eugen.hristev@...rochip.com" <eugen.hristev@...rochip.com>,
        "jic23@...nel.org" <jic23@...nel.org>,
        "nicolas.ferre@...rochip.com" <nicolas.ferre@...rochip.com>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "alexandre.torgue@...com" <alexandre.torgue@...com>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        "ak@...klinger.de" <ak@...klinger.de>,
        "Ardelean, Alexandru" <alexandru.Ardelean@...log.com>
Subject: RE: [PATCH v2 7/8] iio: core: simplify alloc alignment code

Hey Alex,

Just a small question...

> From: linux-iio-owner@...r.kernel.org <linux-iio-owner@...r.kernel.org>
> On Behalf Of Alexandru Ardelean
> Sent: Donnerstag, 14. Mai 2020 15:17
> To: linux-iio@...r.kernel.org; linux-arm-kernel@...ts.infradead.org; linux-
> stm32@...md-mailman.stormreply.com; linux-kernel@...r.kernel.org
> Cc: ludovic.desroches@...rochip.com; eugen.hristev@...rochip.com;
> jic23@...nel.org; nicolas.ferre@...rochip.com;
> alexandre.belloni@...tlin.com; alexandre.torgue@...com;
> mcoquelin.stm32@...il.com; ak@...klinger.de; Ardelean, Alexandru
> <alexandru.Ardelean@...log.com>
> Subject: [PATCH v2 7/8] iio: core: simplify alloc alignment code
> 
> There was a recent discussion about this code:
>   https://urldefense.com/v3/__https://lore.kernel.org/linux-
> iio/20200322165317.0b1f0674@...hlinux/__;!!A3Ni8CS0y2Y!pgdUSayJCfxMiE
> w8Fpv0LkEZurCSkX0sEcLnXeDSCLmhpu1xont6-vBQj3ZbCw$
> 
> This looks like a good time to rework this, since any issues about it
> should pop-up under testing, because the iio_dev is having a bit of an
> overhaul and stuff being moved to iio_dev_priv.
> 
> Signed-off-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
> ---
>  drivers/iio/industrialio-core.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index a1b29e0f8fd6..7671d36efae7 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1514,13 +1514,9 @@ struct iio_dev *iio_device_alloc(int sizeof_priv)
>  	struct iio_dev *dev;
>  	size_t alloc_size;
> 
> -	alloc_size = sizeof(struct iio_dev_opaque);
> -	if (sizeof_priv) {
> -		alloc_size = ALIGN(alloc_size, IIO_ALIGN);
> -		alloc_size += sizeof_priv;
> -	}
> -	/* ensure 32-byte alignment of whole construct ? */
> -	alloc_size += IIO_ALIGN - 1;
> +	alloc_size = ALIGN(sizeof(struct iio_dev_opaque), IIO_ALIGN);
> +	if (sizeof_priv)
> +		alloc_size += ALIGN(sizeof_priv, IIO_ALIGN);

Do we actually need to do the `ALIGN` again? It seems to me that `alloc_size += sizeof_priv`
would be enough or am I missing something obvious?

- Nuno Sá