diff mbox series

can: j1939: add tables for the CAN identifier and its fields

Message ID 20201104155730.25196-1-yegorslists@googlemail.com (mailing list archive)
State Not Applicable
Delegated to: Netdev Maintainers
Headers show
Series can: j1939: add tables for the CAN identifier and its fields | expand

Commit Message

Yegor Yefremov Nov. 4, 2020, 3:57 p.m. UTC 
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>
---
 Documentation/networking/j1939.rst | 46 +++++++++++++++++++++++++++---
 1 file changed, 42 insertions(+), 4 deletions(-)

Comments

Marc Kleine-Budde Nov. 4, 2020, 4:06 p.m. UTC | #1 
On 11/4/20 4:57 PM, yegorslists@googlemail.com wrote:
> 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>
> ---
>  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..19d9878d7194 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) 
> +  ============  ==============  ====================

Here you introduce trailing whitespace. I've removed them while applying the
patch to linux-can/testing

Marc
diff mbox series

Patch

diff --git a/Documentation/networking/j1939.rst b/Documentation/networking/j1939.rst
index 0a4b73b03b99..19d9878d7194 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