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From: Oliver Hartkopp <socketcan@hartkopp.net>
To: Vincent MAILHOL <mailhol.vincent@wanadoo.fr>
Cc: "Marc Kleine-Budde" <mkl@pengutronix.de>,
	linux-can@vger.kernel.org, kernel@pengutronix.de,
	"Stéphane Grosjean" <s.grosjean@peak-system.com>
Subject: Re: [net-rfc 04/16] can: dev: can_get_len(): add a helper function to get the correct length of Classical frames
Date: Sat, 24 Oct 2020 13:31:06 +0200
Message-ID: <358352d1-2428-0909-9bfe-a62e68f47e28@hartkopp.net> (raw)
In-Reply-To: <CAMZ6Rq+tx93DuRYsLOpcxjRDOJxUTh-czntEYSv7tDMOwoaLQw@mail.gmail.com>



On 24.10.20 07:25, Vincent MAILHOL wrote:
> On 24.10.20 01:47, Oliver Hartkopp wrote:

>>>> Btw. do you really see any legacy SocketCAN applications (*together*
>>>> with your testing application on the same Linux host) where you don't
>>>> have the source code to check whether they properly initialize the
>>>> reserved/padding bytes?
>>
>> Do you?

You still didn't answer this hypothetical question. There must be a 
reason behind .. :-D

>> You can not take responsibility for broken implementations on other ECUs.
> 
> We clearly share a difference stance on this subject, I think it is
> time to close the debate. I agree to go with your solution.

Ok, together with this answer I also can close the debate :-)

> I saw your patch. Changing the name from raw_can to len8_dlc clears
> the concerns I had for invalid frames. Thank you.

Great! In fact it cost some time in the night where I woke up from sleep 
and think about "the overall goal what we want to archive" ;-)

The right naming lets developers make right assumptions about the 
functionality. Therefore it always remains tricky - and discussions like 
these. I needed two hours to write an rephrase the patch again and again ...

Also the ctrlmode has now a clear target of Classic CAN (CC) in its 
name: CC_LEN8_DLC

> Thank you also for depreciating the can_dlc field and introducing the
> len field in struct can_frame. It is a smart change.

Thanks. I always had the idea to fix this up after the introduction of 
CAN FD which uses a 'len' element too. I discovered myself at that time, 
that can_dlc was not the best matching choice - but Kernel APIs are 
written in stone for a good reason.

So I've checked what people do, when they need to rename structure 
elements in the Kernel API in the uapi section and found this:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=31ba514b2fd0495796

> I will now test the patch.

So far it only is an idea for naming 'things' - but I'm happy you like it!

IMO we could continue with enabling a CAN driver to support 
CAN_CTRLMODE_CC_LEN8_DLC and see how it works in reality with CAN_RAW 
and AF_PACKET - and if we would finally need CAN_RAW_LEN8_DLC or not.

Best,
Oliver

  reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-19 19:05 [RFC]: can 2020-10-19 Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 01/16] can: proc: can_remove_proc(): silence remove_proc_entry warning Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 02/16] can: rx-offload: don't call kfree_skb() from IRQ context Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 03/16] can: dev: can_get_echo_skb(): prevent call to kfree_skb() in hard " Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 04/16] can: dev: can_get_len(): add a helper function to get the correct length of Classical frames Marc Kleine-Budde
2020-10-19 20:35   ` Oliver Hartkopp
2020-10-20  6:35     ` Marc Kleine-Budde
2020-10-20 11:30       ` Vincent Mailhol
2020-10-20 11:48         ` Marc Kleine-Budde
2020-10-20 12:38         ` Oliver Hartkopp
2020-10-20 15:02           ` Marc Kleine-Budde
2020-10-20 16:07           ` Vincent Mailhol
2020-10-20 17:04             ` Oliver Hartkopp
2020-10-20 18:50               ` Marc Kleine-Budde
2020-10-21  0:52               ` Vincent Mailhol
2020-10-21  6:23                 ` Vincent MAILHOL
2020-10-21  7:11                   ` Joakim Zhang
2020-10-21  7:21                     ` Marc Kleine-Budde
2020-10-21  7:48                       ` Joakim Zhang
2020-10-21  9:21                   ` Oliver Hartkopp
2020-10-21  9:48                     ` Oliver Hartkopp
2020-10-21 11:55                     ` Vincent MAILHOL
2020-10-21 17:52                       ` Oliver Hartkopp
2020-10-22  3:30                         ` Vincent MAILHOL
2020-10-22  7:15                           ` Oliver Hartkopp
2020-10-22 12:23                             ` Vincent MAILHOL
2020-10-22 13:28                               ` Oliver Hartkopp
2020-10-22 15:46                                 ` Vincent MAILHOL
2020-10-22 17:06                                   ` Oliver Hartkopp
2020-10-23 10:36                                     ` Vincent MAILHOL
2020-10-23 16:47                                       ` Oliver Hartkopp
2020-10-24  5:25                                         ` Vincent MAILHOL
2020-10-24 11:31                                           ` Oliver Hartkopp [this message]
2020-10-19 19:05 ` [net-rfc 05/16] can: dev: __can_get_echo_skb(): fix the returned length of CAN frame Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 06/16] can: can_create_echo_skb(): fix echo skb generation: always use skb_clone() Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 07/16] can: j1939: j1939_sk_bind(): return failure if netdev is down Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 08/16] can: isotp: Explain PDU in CAN_ISOTP help text Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 09/16] can: isotp: enable RX timeout handling in listen-only mode Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 10/16] can: ti_hecc: add missed clk_disable_unprepare() in error path Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 11/16] can: xilinx_can: handle failure cases of pm_runtime_get_sync Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 12/16] can: peak_usb: fix timestamp wrapping Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 13/16] can: peak_canfd: fix echo management when loopback is on Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 14/16] can: mcp251xfd: mcp251xfd_regmap_crc_read(): increase severity of CRC read error messages Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 15/16] can: mcp251xfd: mcp251xfd_regmap_nocrc_read(): fix semicolon.cocci warnings Marc Kleine-Budde
2020-10-19 19:05 ` [net-rfc 16/16] can: mcp251xfd: remove unneeded break Marc Kleine-Budde

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