Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.35 as permitted sender) client-ip=23.128.96.35;
Date:   Tue, 3 Oct 2023 12:57:47 +0300
From:   Matti Vaittinen <mazziesaccount@gmail.com>
To:     Matti Vaittinen <mazziesaccount@gmail.com>,
        Matti Vaittinen <matti.vaittinen@fi.rohmeurope.com>
Cc:     Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        linux-iio@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH v6] tools: iio: iio_generic_buffer ensure alignment
Message-ID: <ZRvlm4ktNLu+qmlf@dc78bmyyyyyyyyyyyyydt-3.rev.dnainternet.fi>
MIME-Version: 1.0
Content-Type: multipart/signed; micalg=pgp-sha256;
        protocol="application/pgp-signature"; boundary="X2pRPnCTlVZaKbsj"
Content-Disposition: inline
Precedence: bulk


--X2pRPnCTlVZaKbsj
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable

The iio_generic_buffer can return garbage values when the total size of
scan data is not a multiple of the largest element in the scan. This can be
demonstrated by reading a scan, consisting, for example of one 4-byte and
one 2-byte element, where the 4-byte element is first in the buffer.

The IIO generic buffer code does not take into account the last two
padding bytes that are needed to ensure that the 4-byte data for next
scan is correctly aligned.

Add the padding bytes required to align the next sample with the scan size.

Signed-off-by: Matti Vaittinen <mazziesaccount@gmail.com>
Fixes: e58537ccce73 ("staging: iio: update example application.")

---
Revision history
v5 =3D> v6:
 - fix typo pointed by Andy (wan't =3D> want).
v4 =3D> v5:
 - drop unnecessary comment.
 - drop all other patches as those were already applied.
 - add Fixes-tag.
v3 =3D> v4:
 - drop extra print and TODO coment
 - add comment clarifying alignment sizes
---
 tools/iio/iio_generic_buffer.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/tools/iio/iio_generic_buffer.c b/tools/iio/iio_generic_buffer.c
index 44bbf80f0cfd..0d0a7a19d6f9 100644
--- a/tools/iio/iio_generic_buffer.c
+++ b/tools/iio/iio_generic_buffer.c
@@ -54,9 +54,12 @@ enum autochan {
 static unsigned int size_from_channelarray(struct iio_channel_info *channe=
ls, int num_channels)
 {
 	unsigned int bytes =3D 0;
-	int i =3D 0;
+	int i =3D 0, max =3D 0;
+	unsigned int misalignment;
=20
 	while (i < num_channels) {
+		if (channels[i].bytes > max)
+			max =3D channels[i].bytes;
 		if (bytes % channels[i].bytes =3D=3D 0)
 			channels[i].location =3D bytes;
 		else
@@ -66,6 +69,14 @@ static unsigned int size_from_channelarray(struct iio_ch=
annel_info *channels, in
 		bytes =3D channels[i].location + channels[i].bytes;
 		i++;
 	}
+	/*
+	 * We want the data in next sample to also be properly aligned so
+	 * we'll add padding at the end if needed. Adding padding only
+	 * works for channel data which size is 2^n bytes.
+	 */
+	misalignment =3D bytes % max;
+	if (misalignment)
+		bytes +=3D max - misalignment;
=20
 	return bytes;
 }

base-commit: 0bb80ecc33a8fb5a682236443c1e740d5c917d1d
--=20
2.41.0


--=20
Matti Vaittinen, Linux device drivers
ROHM Semiconductors, Finland SWDC
Kiviharjunlenkki 1E
90220 OULU
FINLAND

~~~ "I don't think so," said Rene Descartes. Just then he vanished ~~~
Simon says - in Latin please.
~~~ "non cogito me" dixit Rene Descarte, deinde evanescavit ~~~
Thanks to Simon Glass for the translation =3D]=20

--X2pRPnCTlVZaKbsj
Content-Type: application/pgp-signature; name="signature.asc"

-----BEGIN PGP SIGNATURE-----

iQEzBAEBCAAdFiEEIx+f8wZb28fLKEhTeFA3/03aocUFAmUb5ZsACgkQeFA3/03a
ocW5wggAlOggIxqFVoJD+8TnfOgo9flg0eq3Cj9dq8lTa1fKH3emYtXpdHkoRS3S
pd8ZuCSFOmQ9r4ijAd4B2488fdtjf+XJPnStVO8eRDKAwgih4o+ri0p05HJzC56l
Ih4fujrRzl1oDtdIJOaGISYTELPF52uvkd7Yw6O6IubgWloZYQ9jzXEQ8ZCFsvMR
Q/SwRomSBroNAUtJwSWthAAteXPZ8lPFxcFUjg84sMKIqR6G9xyx0QioijnCDDwM
eRDzEbKTDGFojVpFYz7ReSl5/YyICM+gHCo5ldueGi2jX86ngrh5rfYEW85qxLG6
w/nqWWm3dmqbRV4313ZfqE16iFkfiA==
=EdzQ
-----END PGP SIGNATURE-----

--X2pRPnCTlVZaKbsj--