Re: [PATCH v5 2/5] iio: pressure: bmp280: Fix alignment for DMA safety

From: Andy Shevchenko <andy.shevchenko@gmail.com>
To: Angel Iglesias <ang.iglesiasg@gmail.com>
Cc: linux-iio <linux-iio@vger.kernel.org>,
	Jonathan Cameron <jic23@kernel.org>,
	Lars-Peter Clausen <lars@metafoo.de>,
	Paul Cercueil <paul@crapouillou.net>,
	Ulf Hansson <ulf.hansson@linaro.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5 2/5] iio: pressure: bmp280: Fix alignment for DMA safety
Date: Mon, 8 Aug 2022 10:53:16 +0200	[thread overview]
Message-ID: <CAHp75Vfanb+tZe_D5_hPWn2BrOEkds9i7AZzD5Xc1M5a9GK6qg@mail.gmail.com> (raw)
In-Reply-To: <49086f5c1401d7d28ebf921a67b49f8403ddb16a.1659872590.git.ang.iglesiasg@gmail.com>

On Sun, Aug 7, 2022 at 1:56 PM Angel Iglesias <ang.iglesiasg@gmail.com> wrote:
>
> Adds DMA-safe buffers to driver data struct to store raw data from sensors
>
> The multiple buffers used thorough the driver share the same memory
> allocated as part of the device data instance. The union containing
> the buffers is aligned to allow safe usage with DMA operations, such
> as regmap bulk read calls.

...

>  #include <linux/completion.h>
>  #include <linux/pm_runtime.h>
>  #include <linux/random.h>

+ Blank line.

> +#include <asm/unaligned.h>

...

> +       union {
> +               /* sensor data buffer */
> +               u8 data[3];
> +               /* calibration data buffers */
> +               __le16 bmp280_cal[BMP280_CONTIGUOUS_CALIB_REGS / 2];
> +               __be16 bmp180_cal[BMP180_REG_CALIB_COUNT / 2];
> +       } buf __aligned(IIO_DMA_MINALIGN);

Hmm... And which field in the struct defines which of the buffers is being used?
Also, do you need a non-anonymous union?

>  };

...

> +       /* parse temperature calibration data */

Be consistent! Check all your patches for the consistency (comments,
other code style, etc).

...

> +       calib->H5 = sign_extend32(((get_unaligned_le16(data->buf.data) >> 4) & 0xfff), 11);

(It's not directly related to this change, but good to ask)
Are you going to change all those masks to use GENMASK()?

...

> +       struct bmp180_calib *calib = &data->calib.bmp180;
>         int ret;
>         int i;
> -       struct bmp180_calib *calib = &data->calib.bmp180;

Exactly my point given the previous patch, now you have a ping-pong
style of changes: the introduced line in the series is being touched
again in the very same series without any need.

...

>         u8 oss = data->oversampling_press;
> +       int ret;

Ditto.

-- 
With Best Regards,
Andy Shevchenko