Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
To:     Vincent Mailhol <mailhol.vincent@wanadoo.fr>,
        linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
        linux-can@vger.kernel.org, Wolfgang Grandegger <wg@grandegger.com>,
        "David S . Miller" <davem@davemloft.net>
Cc:     Jakub Kicinski <kuba@kernel.org>, Oliver Neukum <oneukum@suse.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Arunachalam Santhanam <arunachalam.santhanam@in.bosch.com>,
        "open list:USB ACM DRIVER" <linux-usb@vger.kernel.org>
References: <20200926175810.278529-1-mailhol.vincent@wanadoo.fr>
 <20200930144602.10290-3-mailhol.vincent@wanadoo.fr>
From:   Marc Kleine-Budde <mkl@pengutronix.de>
Autocrypt: addr=mkl@pengutronix.de; prefer-encrypt=mutual; keydata=
 mQINBFFVq30BEACtnSvtXHoeHJxG6nRULcvlkW6RuNwHKmrqoksispp43X8+nwqIFYgb8UaX
 zu8T6kZP2wEIpM9RjEL3jdBjZNCsjSS6x1qzpc2+2ivjdiJsqeaagIgvy2JWy7vUa4/PyGfx
 QyUeXOxdj59DvLwAx8I6hOgeHx2X/ntKAMUxwawYfPZpP3gwTNKc27dJWSomOLgp+gbmOmgc
 6U5KwhAxPTEb3CsT5RicsC+uQQFumdl5I6XS+pbeXZndXwnj5t84M+HEj7RN6bUfV2WZO/AB
 Xt5+qFkC/AVUcj/dcHvZwQJlGeZxoi4veCoOT2MYqfR0ax1MmN+LVRvKm29oSyD4Ts/97cbs
 XsZDRxnEG3z/7Winiv0ZanclA7v7CQwrzsbpCv+oj+zokGuKasofzKdpywkjAfSE1zTyF+8K
 nxBAmzwEqeQ3iKqBc3AcCseqSPX53mPqmwvNVS2GqBpnOfY7Mxr1AEmxdEcRYbhG6Xdn+ACq
 Dq0Db3A++3PhMSaOu125uIAIwMXRJIzCXYSqXo8NIeo9tobk0C/9w3fUfMTrBDtSviLHqlp8
 eQEP8+TDSmRP/CwmFHv36jd+XGmBHzW5I7qw0OORRwNFYBeEuiOIgxAfjjbLGHh9SRwEqXAL
 kw+WVTwh0MN1k7I9/CDVlGvc3yIKS0sA+wudYiselXzgLuP5cQARAQABtCZNYXJjIEtsZWlu
 ZS1CdWRkZSA8bWtsQHBlbmd1dHJvbml4LmRlPokCVAQTAQoAPgIbAwIeAQIXgAULCQgHAwUV
 CgkICwUWAgMBABYhBMFAC6CzmJ5vvH1bXCte4hHFiupUBQJfEWX4BQkQo2czAAoJECte4hHF
 iupUvfMP/iNtiysSr5yU4tbMBzRkGov1/FjurfH1kPweLVHDwiQJOGBz9HgM5+n8boduRv36
 0lU32g3PehN0UHZdHWhygUd6J09YUi2mJo1l2Fz1fQ8elUGUOXpT/xoxNQjslZjJGItCjza8
 +D1DO+0cNFgElcNPa7DFBnglatOCZRiMjo4Wx0i8njEVRU+4ySRU7rCI36KPts+uVmZAMD7V
 3qiR1buYklJaPCJsnXURXYsilBIE9mZRmQjTDVqjLWAit++flqUVmDjaD/pj2AQe2Jcmd2gm
 sYW5P1moz7ACA1GzMjLDmeFtpJOIB7lnDX0F/vvsG3V713/701aOzrXqBcEZ0E4aWeZJzaXw
 n1zVIrl/F3RKrWDhMKTkjYy7HA8hQ9SJApFXsgP334Vo0ea82H3dOU755P89+Eoj0y44MbQX
 7xUy4UTRAFydPl4pJskveHfg4dO6Yf0PGIvVWOY1K04T1C5dpnHAEMvVNBrfTA8qcahRN82V
 /iIGB+KSC2xR79q1kv1oYn0GOnWkvZmMhqGLhxIqHYitwH4Jn5uRfanKYWBk12LicsjRiTyW
 Z9cJf2RgAtQgvMPvmaOL8vB3U4ava48qsRdgxhXMagU618EszVdYRNxGLCqsKVYIDySTrVzu
 ZGs2ibcRhN4TiSZjztWBAe1MaaGk05Ce4h5IdDLbOOxhuQENBF8SDLABCADohJLQ5yffd8Sq
 8Lo9ymzgaLcWboyZ46pY4CCCcAFDRh++QNOJ8l4mEJMNdEa/yrW4lDQDhBWV75VdBuapYoal
 LFrSzDzrqlHGG4Rt4/XOqMo6eSeSLipYBu4Xhg59S9wZOWbHVT/6vZNmiTa3d40+gBg68dQ8
 iqWSU5NhBJCJeLYdG6xxeUEtsq/25N1erxmhs/9TD0sIeX36rFgWldMwKmZPe8pgZEv39Sdd
 B+ykOlRuHag+ySJxwovfdVoWT0o0LrGlHzAYo6/ZSi/Iraa9R/7A1isWOBhw087BMNkRYx36
 B77E4KbyBPx9h3wVyD/R6T0Q3ZNPu6SQLnsWojMzABEBAAGJAjwEGAEKACYWIQTBQAugs5ie
 b7x9W1wrXuIRxYrqVAUCXxIMsAIbDAUJAucGAAAKCRArXuIRxYrqVOu0D/48xSLyVZ5NN2Bb
 yqo3zxdv/PMGJSzM3JqSv7hnMZPQGy9XJaTc5Iz/hyXaNRwpH5X0UNKqhQhlztChuAKZ7iu+
 2VKzq4JJe9qmydRUwylluc4HmGwlIrDNvE0N66pRvC3h8tOVIsippAQlt5ciH74bJYXr0PYw
 Aksw1jugRxMbNRzgGECg4O6EBNaHwDzsVPX1tDj0d9t/7ClzJUy20gg8r9Wm/I/0rcNkQOpV
 RJLDtSbGSusKxor2XYmVtHGauag4YO6Vdq+2RjArB3oNLgSOGlYVpeqlut+YYHjWpaX/cTf8
 /BHtIQuSAEu/WnycpM3Z9aaLocYhbp5lQKL6/bcWQ3udd0RfFR/Gv7eR7rn3evfqNTtQdo4/
 YNmd7P8TS7ALQV/5bNRe+ROLquoAZvhaaa6SOvArcmFccnPeyluX8+o9K3BCdXPwONhsrxGO
 wrPI+7XKMlwWI3O076NqNshh6mm8NIC0mDUr7zBUITa67P3Q2VoPoiPkCL9RtsXdQx5BI9iI
 h/6QlzDxcBdw2TVWyGkVTCdeCBpuRndOMVmfjSWdCXXJCLXO6sYeculJyPkuNvumxgwUiK/H
 AqqdUfy1HqtzP2FVhG5Ce0TeMJepagR2CHPXNg88Xw3PDjzdo+zNpqPHOZVKpLUkCvRv1p1q
 m1qwQVWtAwMML/cuPga78rkBDQRfEXGWAQgAt0Cq8SRiLhWyTqkf16Zv/GLkUgN95RO5ntYM
 fnc2Tr3UlRq2Cqt+TAvB928lN3WHBZx6DkuxRM/Y/iSyMuhzL5FfhsICuyiBs5f3QG70eZx+
 Bdj4I7LpnIAzmBdNWxMHpt0m7UnkNVofA0yH6rcpCsPrdPRJNOLFI6ZqXDQk9VF+AB4HVAJY
 BDU3NAHoyVGdMlcxev0+gEXfBQswEcysAyvzcPVTAqmrDsupnIB2f0SDMROQCLO6F+/cLG4L
 Stbz+S6YFjESyXblhLckTiPURvDLTywyTOxJ7Mafz6ZCene9uEOqyd/h81nZOvRd1HrXjiTE
 1CBw+Dbvbch1ZwGOTQARAQABiQNyBBgBCgAmFiEEwUALoLOYnm+8fVtcK17iEcWK6lQFAl8R
 cZYCGwIFCQLnoRoBQAkQK17iEcWK6lTAdCAEGQEKAB0WIQQreQhYm33JNgw/d6GpyVqK+u3v
 qQUCXxFxlgAKCRCpyVqK+u3vqatQCAC3QIk2Y0g/07xNLJwhWcD7JhIqfe7Qc5Vz9kf8ZpWr
 +6w4xwRfjUSmrXz3s6e/vrQsfdxjVMDFOkyG8c6DWJo0TVm6Ucrf9G06fsjjE/6cbE/gpBkk
 /hOVz/a7UIELT+HUf0zxhhu+C9hTSl8Nb0bwtm6JuoY5AW0LP2KoQ6LHXF9KNeiJZrSzG6WE
 h7nf3KRFS8cPKe+trbujXZRb36iIYUfXKiUqv5xamhohy1hw+7Sy8nLmw8rZPa40bDxX0/Gi
 98eVyT4/vi+nUy1gF1jXgNBSkbTpbVwNuldBsGJsMEa8lXnYuLzn9frLdtufUjjCymdcV/iT
 sFKziU9AX7TLZ5AP/i1QMP9OlShRqERH34ufA8zTukNSBPIBfmSGUe6G2KEWjzzNPPgcPSZx
 Do4jfQ/m/CiiibM6YCa51Io72oq43vMeBwG9/vLdyev47bhSfMLTpxdlDJ7oXU9e8J61iAF7
 vBwerBZL94I3QuPLAHptgG8zPGVzNKoAzxjlaxI1MfqAD9XUM80MYBVjunIQlkU/AubdvmMY
 X7hY1oMkTkC5hZNHLgIsDvWUG0g3sACfqF6gtMHY2lhQ0RxgxAEx+ULrk/svF6XGDe6iveyc
 z5Mg5SUggw3rMotqgjMHHRtB3nct6XqgPXVDGYR7nAkXitG+nyG5zWhbhRDglVZ0mLlW9hij
 z3Emwa94FaDhN2+1VqLFNZXhLwrNC5mlA6LUjCwOL+zb9a07HyjekLyVAdA6bZJ5BkSXJ1CO
 5YeYolFjr4YU7GXcSVfUR6fpxrb8N+yH+kJhY3LmS9vb2IXxneE/ESkXM6a2YAZWfW8sgwTm
 0yCEJ41rW/p3UpTV9wwE2VbGD1XjzVKl8SuAUfjjcGGys3yk5XQ5cccWTCwsVdo2uAcY1MVM
 HhN6YJjnMqbFoHQq0H+2YenTlTBn2Wsp8TIytE1GL6EbaPWbMh3VLRcihlMj28OUWGSERxat
 xlygDG5cBiY3snN3xJyBroh5xk/sHRgOdHpmujnFyu77y4RTZ2W8
Subject: Re: [PATCH v2 2/6] can: dev: add a helper function to get the correct
 length of Classical frames
Message-ID: <1798400d-abc1-e6dd-2d19-41e82ca6e43e@pengutronix.de>
Date:   Wed, 30 Sep 2020 17:21:20 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101
 Thunderbird/68.12.0
MIME-Version: 1.0
In-Reply-To: <20200930144602.10290-3-mailhol.vincent@wanadoo.fr>
Content-Type: multipart/signed; micalg=pgp-sha512;
 protocol="application/pgp-signature";
 boundary="sQZpGVhjMHWRxljLBs1RfHjAtMSzlvl89"
Precedence: bulk

This is an OpenPGP/MIME signed message (RFC 4880 and 3156)
--sQZpGVhjMHWRxljLBs1RfHjAtMSzlvl89
Content-Type: multipart/mixed; boundary="0PLD90LKZkF4UcdYyOK9gT6o0Z49KwvvP";
 protected-headers="v1"
From: Marc Kleine-Budde <mkl@pengutronix.de>
To: Vincent Mailhol <mailhol.vincent@wanadoo.fr>,
 linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
 linux-can@vger.kernel.org, Wolfgang Grandegger <wg@grandegger.com>,
 "David S . Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>, Oliver Neukum <oneukum@suse.com>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
 Masahiro Yamada <masahiroy@kernel.org>,
 Arunachalam Santhanam <arunachalam.santhanam@in.bosch.com>,
 "open list:USB ACM DRIVER" <linux-usb@vger.kernel.org>
Message-ID: <1798400d-abc1-e6dd-2d19-41e82ca6e43e@pengutronix.de>
Subject: Re: [PATCH v2 2/6] can: dev: add a helper function to get the correct
 length of Classical frames
References: <20200926175810.278529-1-mailhol.vincent@wanadoo.fr>
 <20200930144602.10290-3-mailhol.vincent@wanadoo.fr>
In-Reply-To: <20200930144602.10290-3-mailhol.vincent@wanadoo.fr>

--0PLD90LKZkF4UcdYyOK9gT6o0Z49KwvvP
Content-Type: text/plain; charset=utf-8
Content-Language: de-DE
Content-Transfer-Encoding: quoted-printable

On 9/30/20 4:45 PM, Vincent Mailhol wrote:
> In classical CAN, the length of the data (i.e. CAN payload) is not
> always equal to the DLC! If the frame is a Remote Transmission Request
> (RTR), data length is always zero regardless of DLC value and else, if
> the DLC is greater than 8, the length is 8. Contrary to common belief,
> ISO 11898-1 Chapter 8.4.2.3 (DLC field) do allow DLCs greater than 8
> for Classical Frames and specifies that those DLCs shall indicate that
> the data field is 8 bytes long.
>=20
> Above facts are widely unknown and so many developpers uses the "len"
> field of "struct canfd_frame" to get the length of classical CAN
> frames: this is incorrect!
>=20
> This patch introduces function get_can_len() which can be used in
> remediation. The function takes the SKB as an input in order to be
> able to determine if the frame is classical or FD.
>=20
> Signed-off-by: Vincent Mailhol <mailhol.vincent@wanadoo.fr>
> ---
>  include/linux/can/dev.h | 23 +++++++++++++++++++++++
>  1 file changed, 23 insertions(+)
>=20
> diff --git a/include/linux/can/dev.h b/include/linux/can/dev.h
> index 5e3d45525bd3..72a8a60c0094 100644
> --- a/include/linux/can/dev.h
> +++ b/include/linux/can/dev.h
> @@ -177,6 +177,29 @@ u8 can_dlc2len(u8 can_dlc);
>  /* map the sanitized data length to an appropriate data length code */=

>  u8 can_len2dlc(u8 len);
> =20
> +/*
> + * get_can_len(skb) - get the length of the CAN payload.
> + *
> + * In classical CAN, the length of the data (i.e. CAN payload) is not
> + * always equal to the DLC! If the frame is a Remote Transmission
> + * Request (RTR), data length is always zero regardless of DLC value
> + * and else, if the DLC is greater than 8, the length is 8. Contrary
> + * to common belief, ISO 11898-1 Chapter 8.4.2.3 (DLC field) do allow
> + * DLCs greater than 8 for Classical Frames and specifies that those
> + * DLCs shall indicate that the data field is 8 bytes long.
> + */
> +static inline int get_can_len(struct sk_buff *skb)

make this return an u8
make the skb const

> +{
> +	struct canfd_frame *cf =3D (struct canfd_frame *)skb->data;

const

> +
> +	if (can_is_canfd_skb(skb))
> +		return min_t(__u8, cf->len, CANFD_MAX_DLEN);

u8

> +	else if (cf->can_id & CAN_RTR_FLAG)
> +		return 0;
> +	else
> +		return min_t(__u8, cf->len, CAN_MAX_DLEN);

u8

> +}
> +
>  struct net_device *alloc_candev_mqs(int sizeof_priv, unsigned int echo=
_skb_max,
>  				    unsigned int txqs, unsigned int rxqs);
>  #define alloc_candev(sizeof_priv, echo_skb_max) \
>=20

Marc

--=20
Pengutronix e.K.                 | Marc Kleine-Budde           |
Embedded Linux                   | https://www.pengutronix.de  |
Vertretung West/Dortmund         | Phone: +49-231-2826-924     |
Amtsgericht Hildesheim, HRA 2686 | Fax:   +49-5121-206917-5555 |


--0PLD90LKZkF4UcdYyOK9gT6o0Z49KwvvP--

--sQZpGVhjMHWRxljLBs1RfHjAtMSzlvl89
Content-Type: application/pgp-signature; name="signature.asc"
Content-Description: OpenPGP digital signature
Content-Disposition: attachment; filename="signature.asc"

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

iQEzBAEBCgAdFiEEK3kIWJt9yTYMP3ehqclaivrt76kFAl90onEACgkQqclaivrt
76mXMAgAjc5YqTfkyCIYKMyMeKBJZKhx1QY+odwh4T8OgwSQrPdmGj1qxYBLkubX
P9pIMNts966DbfZZQudqFg4L8ZjAdmy1fGJN3pl8FZk9idi+QWfUZzQ54AHNwxFn
7BbPmY8aAVjP35P5XyM+fZjgEX6up4NllmqEHdPuWUwjpx6UvfytCKFu4MlJDSjr
c5T7fAkQdYZOiSgz9zQvgfcfXZ2/mVWPA1jfBa8zSkjV2E1F9exxSqNLGr22MSQt
gHQdrjUlfv3911YcXOX5wTFisjlOKZBTasXFGlILJuwZs/IXNRckdHUmcU/Sz+Al
lDyYsezsC27SrDXsEl5Cx1Y217YFAw==
=zF8r
-----END PGP SIGNATURE-----

--sQZpGVhjMHWRxljLBs1RfHjAtMSzlvl89--