Re: [RFC PATCH] can: add tx/rx led trigger support

[Wolfgang Grandegger <wg@grandegger.com>]

On 04/12/2012 07:46 PM, Fabio Baltieri wrote:
> On Thu, Apr 12, 2012 at 9:37 AM, Wolfgang Grandegger <wg@grandegger.com> wrote:
>>> It stays on for some time after each frame. Above a certain
>>> packet-rate (1/led_off_delay) LED appear to be constantly on. You can
>>> tell periodic packets from bursts from it but nothing more.
>>
>> Concerning the LED control (on. off, blinking), could that not be
>> done/configured in the generic LED interface (via sysfs files)? That
>> seems the right place for me. Then the CAN LED software just needs to
>> send the trigger which would significantly simplify the code (without
>> timer).
> 
> Of course, that's possible, but I think a kernel implementation with
> timers for blinking and some well placed trigger points would be more
> effective that, for example, polling interface stats from userspace.
> After all many other subsystems have similar triggers in kernel space
> (netfilter, ide/ata with timers, mtd, mmc, mac80211 without triggers).

See my previous mail.

>> Furthermore, if I understand your patch correctly, the LEDs with the
>> names "canX-rx" and "canX-tx" are directly assigned (hardwired). A more
>> flexible method would be appreciated, if it could be realized with just
>> a little more code.
> 
> Well, they are just sprintf-ed from initial interface name, that's
> also how mac80211 implementation works. Can you be more specific on
> how should I change it? Like following interface rename or so?

The LED could be assigned when configuring the CAN interface:

  ip ... type can rx-led "the-can-rx-led"

But maybe it's overkill and we even misuse the ip tool. I still think
that the LED interface should be very slim.

Wolfgang.