From: Marc Kleine-Budde <mkl@pengutronix.de>
To: netdev@vger.kernel.org
Cc: davem@davemloft.net, kuba@kernel.org, linux-can@vger.kernel.org,
kernel@pengutronix.de,
Yegor Yefremov <yegorslists@googlemail.com>,
Marc Kleine-Budde <mkl@pengutronix.de>
Subject: [net-next 01/25] can: j1939: add tables for the CAN identifier and its fields
Date: Fri, 20 Nov 2020 14:32:54 +0100 [thread overview]
Message-ID: <20201120133318.3428231-2-mkl@pengutronix.de> (raw)
In-Reply-To: <20201120133318.3428231-1-mkl@pengutronix.de>
From: Yegor Yefremov <yegorslists@googlemail.com>
Use table markup to show the structure of the CAN identifier, PGN, PDU1, and
PDU2 formats. Also add introductory sentence.
Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Link: https://lore.kernel.org/r/20201104155730.25196-1-yegorslists@googlemail.com
[mkl: removed trailing whitespace]
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
---
Documentation/networking/j1939.rst | 46 +++++++++++++++++++++++++++---
1 file changed, 42 insertions(+), 4 deletions(-)
diff --git a/Documentation/networking/j1939.rst b/Documentation/networking/j1939.rst
index 0a4b73b03b99..b705d2801e9c 100644
--- a/Documentation/networking/j1939.rst
+++ b/Documentation/networking/j1939.rst
@@ -69,18 +69,56 @@ J1939 concepts
PGN
---
+The J1939 protocol uses the 29-bit CAN identifier with the following structure:
+
+ ============ ============== ====================
+ 29 bit CAN-ID
+ --------------------------------------------------
+ Bit positions within the CAN-ID
+ --------------------------------------------------
+ 28 ... 26 25 ... 8 7 ... 0
+ ============ ============== ====================
+ Priority PGN SA (Source Address)
+ ============ ============== ====================
+
The PGN (Parameter Group Number) is a number to identify a packet. The PGN
is composed as follows:
-1 bit : Reserved Bit
-1 bit : Data Page
-8 bits : PF (PDU Format)
-8 bits : PS (PDU Specific)
+
+ ============ ============== ================= =================
+ PGN
+ ------------------------------------------------------------------
+ Bit positions within the CAN-ID
+ ------------------------------------------------------------------
+ 25 24 23 ... 16 15 ... 8
+ ============ ============== ================= =================
+ R (Reserved) DP (Data Page) PF (PDU Format) PS (PDU Specific)
+ ============ ============== ================= =================
In J1939-21 distinction is made between PDU1 format (where PF < 240) and PDU2
format (where PF >= 240). Furthermore, when using the PDU2 format, the PS-field
contains a so-called Group Extension, which is part of the PGN. When using PDU2
format, the Group Extension is set in the PS-field.
+ ============== ========================
+ PDU1 Format (specific) (peer to peer)
+ ----------------------------------------
+ Bit positions within the CAN-ID
+ ----------------------------------------
+ 23 ... 16 15 ... 8
+ ============== ========================
+ 00h ... EFh DA (Destination address)
+ ============== ========================
+
+ ============== ========================
+ PDU2 Format (global) (broadcast)
+ ----------------------------------------
+ Bit positions within the CAN-ID
+ ----------------------------------------
+ 23 ... 16 15 ... 8
+ ============== ========================
+ F0h ... FFh GE (Group Extenstion)
+ ============== ========================
+
On the other hand, when using PDU1 format, the PS-field contains a so-called
Destination Address, which is _not_ part of the PGN. When communicating a PGN
from user space to kernel (or vice versa) and PDU2 format is used, the PS-field
base-commit: 4082c502bf9c8a6afe4268c654d4e93ab7dfeb69
--
2.29.2
next prev parent reply other threads:[~2020-11-20 13:34 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 13:32 pull-request: can-next 2020-11-20 Marc Kleine-Budde
2020-11-20 13:32 ` Marc Kleine-Budde [this message]
2020-11-20 13:32 ` [net-next 02/25] can: add optional DLC element to Classical CAN frame structure Marc Kleine-Budde
2020-11-20 13:32 ` [net-next 03/25] can: rename get_can_dlc() macro with can_cc_dlc2len() Marc Kleine-Budde
2020-11-20 13:32 ` [net-next 04/25] can: remove obsolete get_canfd_dlc() macro Marc Kleine-Budde
2020-11-20 13:32 ` [net-next 05/25] can: replace can_dlc as variable/element for payload length Marc Kleine-Budde
2020-11-20 13:32 ` [net-next 06/25] can: rename CAN FD related can_len2dlc and can_dlc2len helpers Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 07/25] can: update documentation for DLC usage in Classical CAN Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 08/25] can: drivers: introduce helpers to access Classical CAN DLC values Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 09/25] can: drivers: add len8_dlc support for various CAN adapters Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 10/25] can: drivers: add len8_dlc support for esd_usb2 CAN adapter Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 11/25] can: gw: support modification of Classical CAN DLCs Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 12/25] dt-bindings: can: fsl,flexcan: add uint32 reference to clock-frequency property Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 13/25] dt-bindings: can: fsl,flexcan: fix fsl,clk-source property Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 14/25] dt-bindings: firmware: add IMX_SC_R_CAN(x) macro for CAN Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 15/25] can: flexcan: rename macro FLEXCAN_QUIRK_SETUP_STOP_MODE -> FLEXCAN_QUIRK_SETUP_STOP_MODE_GPR Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 16/25] can: flexcan: factor out enabling and disabling of interrupts into separate function Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 17/25] can: flexcan: move enabling/disabling of interrupts from flexcan_chip_{start,stop}() to callers Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 18/25] can: flexcan: flexcan_rx_offload_setup(): factor out mailbox and rx-offload setup into separate function Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 19/25] can: flexcan: flexcan_open(): completely initialize controller before requesting IRQ Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 20/25] can: flexcan: flexcan_close(): change order if commands to properly shut down the controller Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 21/25] can: kvaser_usb: Add USB_{LEAF,HYDRA}_PRODUCT_ID_END defines Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 22/25] can: kvaser_usb: Add new Kvaser Leaf v2 devices Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 23/25] can: kvaser_usb: kvaser_usb_hydra: Add support for new device variant Marc Kleine-Budde
2020-11-20 13:33 ` [net-next 24/25] can: kvaser_usb: Add new Kvaser hydra devices Marc Kleine-Budde
2020-11-20 13:44 ` [PATCH 25/25] can: mcp251xfd: remove useless code in mcp251xfd_chip_softreset Marc Kleine-Budde
2020-11-21 23:09 ` pull-request: can-next 2020-11-20 Jakub Kicinski
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