From: Wolfgang Grandegger <wg-5Yr1BZd7O62+XT7JhA+gdA@public•gmane.org>
To: Arnd Bergmann <arnd-r2nGTMty4D4@public•gmane.org>
Cc: sachi-EvXpCiN+lbve9wHmmfpqLFaTQe2KTcn/@public.gmane.org,
davinci-linux-open-source-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/@public.gmane.org,
Subhasish Ghosh
<subhasish-EvXpCiN+lbve9wHmmfpqLFaTQe2KTcn/@public.gmane.org>,
nsekhar-l0cyMroinI0@public•gmane.org,
open list <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public•gmane.org>,
CAN NETWORK DRIVERS
<socketcan-core-0fE9KPoRgkgATYTw5x5z8w@public•gmane.org>,
Marc Kleine-Budde <mkl-bIcnvbaLZ9MEGnE8C9+IrQ@public•gmane.org>,
Netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
m-watkins-l0cyMroinI0@public•gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public•gmane.org
Subject: Re: [PATCH v4 1/1] can: add pruss CAN driver.
Date: Wed, 04 May 2011 16:33:59 +0200 [thread overview]
Message-ID: <4DC163D7.9010309@grandegger.com> (raw)
In-Reply-To: <201105041511.54095.arnd-r2nGTMty4D4@public.gmane.org>
Hi Arnd,
On 05/04/2011 03:11 PM, Arnd Bergmann wrote:
> On Wednesday 04 May 2011, Subhasish Ghosh wrote:
>> CAN requires mail box IDs to be programmed in. But, the socket
>> CAN subsystem supports only software filtering of the mail box IDs.
>>
>> So, the mail box IDs programmed into socket CAN during initialization
>> does not propagate into the hardware. This is planned to be a future
>> implementation in Socket CAN.
>>
>> In our case, we support hardware filtering, to work around with this,
>> Wolfgang (Socket CAN owner) suggested that we implement
>> this using sysfs.
>>
>> These setting are not for debugging, but to program the mail box IDs
>> into the hardware.
>
> Ok, I see. Can you point me to that discussion?
>
> Wolfgang, I'm a bit worried by the API being split between sockets and sysfs.
> The problem is that once the sysfs API is established, users will start
> relying on it, and you can no longer migrate away from it, even when
> a later version of the Socket CAN also supports setting through a different
> interface. What is the current interface to set mail box IDs in software?
Note that this CAN controller is *very* special. It cannot handle all
CAN id's due to a lack or resources. The PRUSS firmware is able to
manage just up to 8 different CAN identifiers out of the usual 4096
(12-bit) or even more for the extended CAN ids using 29 bits. There is
no other CAN controller with such rather serious limitations and
therefore there exists also no appropriate interface. I think using
sysfs is OK for such device-specific parameters, at least for the time
being.
> How hard would it be to implement that feature in Socket CAN?
CAN controllers usually provide some kind of hardware CAN id filtering,
but in a very hardware dependent way. A generic interface may be able to
handle the PRUSS restrictions as well. CAN devices are usually
configured through the netlink interface. e.g.
$ ip link set can0 up type can bitrate 125000
and such a common interface would be netlink based as well.
> Is that something that Subhasish or someone else could to as a prerequisite
> to merging the driver?
Any ideas on how to handle hardware filtering in a generic way are
welcome. I will try to come up with a proposal sooner than later.
Wolfgang.
next prev parent reply other threads:[~2011-05-04 14:33 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1303474267-6344-1-git-send-email-subhasish@mistralsolutions.com>
2011-04-22 12:11 ` [PATCH v4 1/1] can: add pruss CAN driver Subhasish Ghosh
[not found] ` <1303474267-6344-2-git-send-email-subhasish-EvXpCiN+lbve9wHmmfpqLFaTQe2KTcn/@public.gmane.org>
2011-04-22 15:50 ` Marc Kleine-Budde
[not found] ` <4DB1A3B7.7060300-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
2011-04-25 20:06 ` Wolfgang Grandegger
[not found] ` <4DB5D452.9050500-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-04-27 13:08 ` Subhasish Ghosh
2011-04-27 13:21 ` Marc Kleine-Budde
2011-04-27 13:25 ` Arnd Bergmann
[not found] ` <201104271525.28512.arnd-r2nGTMty4D4@public.gmane.org>
2011-05-04 7:13 ` Subhasish Ghosh
2011-05-04 13:11 ` Arnd Bergmann
[not found] ` <201105041511.54095.arnd-r2nGTMty4D4@public.gmane.org>
2011-05-04 14:33 ` Wolfgang Grandegger [this message]
[not found] ` <4DC163D7.9010309-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-05-04 14:48 ` Arnd Bergmann
[not found] ` <201105041648.37199.arnd-r2nGTMty4D4@public.gmane.org>
2011-05-04 16:00 ` Wolfgang Grandegger
[not found] ` <4DC17831.3070801-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-05-10 10:11 ` Subhasish Ghosh
2011-05-10 10:27 ` Alan Cox
[not found] ` <20110510112734.54160824-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
2011-05-10 12:21 ` Subhasish Ghosh
2011-05-11 21:31 ` Arnd Bergmann
[not found] ` <201105112331.47954.arnd-r2nGTMty4D4@public.gmane.org>
2011-05-11 21:44 ` Arnd Bergmann
[not found] ` <201105112344.44171.arnd-r2nGTMty4D4@public.gmane.org>
2011-05-11 22:39 ` Marc Kleine-Budde
2011-05-11 22:56 ` Alan Cox
[not found] ` <20110511235652.7ccddb3b-qBU/x9rampVanCEyBjwyrvXRex20P6io@public.gmane.org>
2011-05-12 3:03 ` can: hardware vs. software filter Kurt Van Dijck
2011-05-12 7:13 ` [PATCH v4 1/1] can: add pruss CAN driver Wolfgang Grandegger
[not found] ` <4DCB88A4.2010901-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-05-12 10:58 ` Kurt Van Dijck
2011-05-12 12:54 ` Arnd Bergmann
[not found] ` <201105121454.47781.arnd-r2nGTMty4D4@public.gmane.org>
2011-05-12 13:04 ` Marc Kleine-Budde
2011-05-12 14:41 ` Oliver Hartkopp
[not found] ` <4DCBF1B6.6000104-fJ+pQTUTwRTk1uMJSBkQmQ@public.gmane.org>
2011-05-22 10:30 ` Arnd Bergmann
[not found] ` <201105221230.56243.arnd-r2nGTMty4D4@public.gmane.org>
2011-05-23 6:21 ` Oliver Hartkopp
[not found] ` <4DD9FCFC.10803-fJ+pQTUTwRTk1uMJSBkQmQ@public.gmane.org>
2011-05-23 8:23 ` Marc Kleine-Budde
2011-05-27 8:31 ` Wolfgang Grandegger
2011-05-12 7:04 ` Wolfgang Grandegger
2011-05-04 15:57 ` Kurt Van Dijck
2011-05-04 16:09 ` Wolfgang Grandegger
[not found] ` <4DC17A31.8070409@grandegger.com>
[not found] ` <4DC17A31.8070409-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-05-04 20:55 ` Oliver Hartkopp
2011-04-27 13:28 ` Wolfgang Grandegger
[not found] ` <4DB81A12.1000006-5Yr1BZd7O62+XT7JhA+gdA@public.gmane.org>
2011-04-27 13:34 ` Wolfgang Grandegger
2011-04-24 11:13 ` Marc Kleine-Budde
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