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Tue, 20 Oct 2020 15:02:05 +0000 (UTC) To: Oliver Hartkopp , Vincent Mailhol , linux-can@vger.kernel.org Cc: kernel@pengutronix.de References: <20201019190524.1285319-1-mkl@pengutronix.de> <20201019190524.1285319-5-mkl@pengutronix.de> <20201020113023.102360-1-mailhol.vincent@wanadoo.fr> <6f869e47-9a76-3398-0b64-2d573d412f4c@hartkopp.net> From: Marc Kleine-Budde 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: [net-rfc 04/16] can: dev: can_get_len(): add a helper function to get the correct length of Classical frames Message-ID: <24c434cf-95c2-8936-387b-cb651c029781@pengutronix.de> Date: Tue, 20 Oct 2020 17:02:00 +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: <6f869e47-9a76-3398-0b64-2d573d412f4c@hartkopp.net> Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="6J4asT8MMVYpZxa9HQ6JSLbxtwJQV0cey" X-SA-Exim-Connect-IP: 2001:67c:670:201:5054:ff:fe8d:eefb X-SA-Exim-Mail-From: mkl@pengutronix.de X-SA-Exim-Scanned: No (on metis.ext.pengutronix.de); SAEximRunCond expanded to false X-PTX-Original-Recipient: linux-can@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-can@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --6J4asT8MMVYpZxa9HQ6JSLbxtwJQV0cey Content-Type: multipart/mixed; boundary="dcpv7nOdHbfSFXAt9uBJnw4lNKvP67MV6"; protected-headers="v1" From: Marc Kleine-Budde To: Oliver Hartkopp , Vincent Mailhol , linux-can@vger.kernel.org Cc: kernel@pengutronix.de Message-ID: <24c434cf-95c2-8936-387b-cb651c029781@pengutronix.de> Subject: Re: [net-rfc 04/16] can: dev: can_get_len(): add a helper function to get the correct length of Classical frames References: <20201019190524.1285319-1-mkl@pengutronix.de> <20201019190524.1285319-5-mkl@pengutronix.de> <20201020113023.102360-1-mailhol.vincent@wanadoo.fr> <6f869e47-9a76-3398-0b64-2d573d412f4c@hartkopp.net> In-Reply-To: <6f869e47-9a76-3398-0b64-2d573d412f4c@hartkopp.net> --dcpv7nOdHbfSFXAt9uBJnw4lNKvP67MV6 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 10/20/20 2:38 PM, Oliver Hartkopp wrote: [...] > You can create a DLC of 13 for Classical CAN. And your CAN controller=20 > gets 8 bytes from it and says to the network layer: Here is a CAN frame= =20 > with 8 bytes payload. >=20 > Have you ever read out a CAN controller register and found a value=20 > greater than 8 on the register of the DLC value? >=20 > I believe you didn't. The CAN controller sees the DLC but provides 8=20 > bytes as DLC=3D8. I just checked on the flexcan (mx6) and the mcp2518fd. I hardcoded a TX-d= lc of 12 in both drivers and printed the raw dlc value in the RX-path: > Oct 20 16:46:08 riot kernel: flexcan_mailbox_read: dlc=3D12 > Oct 20 16:46:10 riot kernel: mcp251xfd_hw_rx_obj_to_skb: dlc=3D12 The userspace shows a consistent len=3D8. If we want to support CAN-2.0 with DLC > 8, we have to audit the TX-path = every driver and remove the can_dropped_invalid_skb() check. I'm not sure what to do about the RX, with breaking user space ABI. 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 | --dcpv7nOdHbfSFXAt9uBJnw4lNKvP67MV6-- --6J4asT8MMVYpZxa9HQ6JSLbxtwJQV0cey Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCgAdFiEEK3kIWJt9yTYMP3ehqclaivrt76kFAl+O++gACgkQqclaivrt 76n/ngf/RvVztR9suqht8qj3Vmx+SxuExh4kkkEPlDcL5e63G9UlHK9iil4tg6nT HF6HS+CUc4XFE+9/bcGeCjrD50kEMcPkAQtqMwmJjcdCy93pspU7KRwG4od4zdmJ gG4PO7lB0fMzWITFAMGFT34a5iJpcOhQoqHKaaaYR+7G02yl8PKOPU0YclSu6D+z ogqv8U+abcRJUWpBxuX+rROXhIobygSZyk0hisD+Bj1lnpn32vcqv2wwC/ZCjCiK axUx7/RBRCGBEcYW5lP8hIOUYh/cAlZ8C3mlz+LBTKXpYL6A2EshqAvCzAo+xujP 1adOEak27B+jUg7olc03jT8l6HUP0Q== =jP1e -----END PGP SIGNATURE----- --6J4asT8MMVYpZxa9HQ6JSLbxtwJQV0cey--