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From: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
To: Linus Walleij <linus.walleij@linaro.org>
Cc: Jonathan Cameron <jic23@kernel.org>,
	linux-iio <linux-iio@vger.kernel.org>,
	Stephan Gerhold <stephan@gerhold.net>
Subject: Re: [PATCH 16/19] iio: magn: bmc150: Fix buffer alignment in iio_push_to_buffers_with_timestamp()
Date: Fri, 7 May 2021 10:23:33 +0100	[thread overview]
Message-ID: <20210507102333.00004e07@Huawei.com> (raw)
In-Reply-To: <CACRpkdbYemUZCPwET4=dCGcJUfph3En+STtNphK8fbN0er1Z3Q@mail.gmail.com>

On Wed, 5 May 2021 14:57:12 +0200
Linus Walleij <linus.walleij@linaro.org> wrote:

> On Sat, May 1, 2021 at 7:03 PM Jonathan Cameron <jic23@kernel.org> wrote:
> 
> > From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> >
> > To make code more readable, use a structure to express the channel
> > layout and ensure the timestamp is 8 byte aligned.
> >
> > Found during an audit of all calls of uses of
> > iio_push_to_buffers_with_timestamp()
> >
> > Fixes: c91746a2361d ("iio: magn: Add support for BMC150 magnetometer")
> > Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> > Cc: Stephan Gerhold <stephan@gerhold.net>
> > Cc: Linus Walleij <linus.walleij@linaro.org>  
> 
> Excellent work Jonathan.
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
> 
> I wonder if there is some way for us to abstract this into the core so
> we can't get it wrong.

Abstracting is a bit of a pain, because we end up creating unnecessary
limitations on what can be done.  Often having buffer a lot larger than
it needs to be is sensible for example...

However, I'm definitely thinking we should look at what checks we can
add once all these cases are fixed and there might be a nice
pattern to use for those cases where we currently have a bounce buffer
anyway due to hardware restrictions.  In most others, moving to the pattern
where the timestamp is explicit in the structure makes it obvious (subject
to the fun question of x86_32 alignment and whether that matters - we don't
know of any bugs as a result but it's possible some buffer consumer will assume
8 byte alignment - hence the hardening in these cases).

The size being too small case for example should be easy - we just augment
iio_push_to_buffers_with_timestamp() to take the size and check it against
scan_bytes.  Alignment is trickier... 

Jonathan


> Yours,
> Linus Walleij


  reply	other threads:[~2021-05-07  9:25 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-01 17:01 [PATCH 00/19] IIO: Alignment fixes part 2 - struct used to ensure alignment Jonathan Cameron
2021-05-01 17:01 ` [PATCH 01/19] iio: accel: bma180: Fix buffer alignment in iio_push_to_buffers_with_timestamp() Jonathan Cameron
2021-05-13 17:22   ` Jonathan Cameron
2021-05-01 17:01 ` [PATCH 02/19] iio: accel: bma220: " Jonathan Cameron
2021-05-13 17:26   ` Jonathan Cameron
2021-05-01 17:01 ` [PATCH 03/19] iio: accel: hid: " Jonathan Cameron
2021-05-13 17:28   ` Jonathan Cameron
2021-05-01 17:01 ` [PATCH 04/19] iio: accel: kxcjk-1013: " Jonathan Cameron
2021-05-01 19:10   ` Andy Shevchenko
2021-05-13 17:33     ` Jonathan Cameron
2021-05-01 17:01 ` [PATCH 05/19] iio: accel: mxc4005: Fix overread of data and alignment issue Jonathan Cameron
2021-05-13 17:37   ` Jonathan Cameron
2021-05-01 17:01 ` [PATCH 06/19] iio: accel: stk8312: Fix buffer alignment in iio_push_to_buffers_with_timestamp() Jonathan Cameron
2021-05-13 17:39   ` Jonathan Cameron
2021-05-01 17:01 ` [PATCH 07/19] iio: accel: stk8ba50: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 08/19] iio: adc: ti-ads1015: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 09/19] iio: adc: vf610: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 10/19] iio: gyro: bmg160: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 11/19] iio: humidity: am2315: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 12/19] iio: prox: srf08: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 13/19] iio: prox: pulsed-light: " Jonathan Cameron
2021-05-06  6:46   ` Matt Ranostay
2021-05-01 17:01 ` [PATCH 14/19] iio: prox: as3935: " Jonathan Cameron
2021-05-06  6:45   ` Matt Ranostay
2021-05-01 17:01 ` [PATCH 15/19] iio: magn: hmc5843: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 16/19] iio: magn: bmc150: " Jonathan Cameron
2021-05-05 12:57   ` Linus Walleij
2021-05-07  9:23     ` Jonathan Cameron [this message]
2021-05-13 17:50   ` Jonathan Cameron
2021-05-01 17:01 ` [PATCH 17/19] iio: light: isl29125: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 18/19] iio: light: tcs3414: " Jonathan Cameron
2021-05-01 17:01 ` [PATCH 19/19] iio: light: tcs3472: " Jonathan Cameron
2021-05-01 19:09   ` Andy Shevchenko
2021-05-01 19:12 ` [PATCH 00/19] IIO: Alignment fixes part 2 - struct used to ensure alignment Andy Shevchenko
2021-05-13 17:54   ` Jonathan Cameron

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