Re: [PATCH 10/11] LED: Add IDE disk activity LED trigger

[Benjamin Herrenschmidt <benh@kernel.crashing.org>]

> Ben, code in pmac.c (+ block layer) seems to be doing something
> different then Kconfig help entry states ("Blink laptop LED on drive
> activity")?
> 
> > I'll experiment with the feasibility of the block later as I've always
> > been uneasy about the hooks into the lower level layers. There are a
> > number of issues to consider though.

The hook in the block layer was Jens idea :)

> At worst it should be handled at host driver level not device driver
> (like pmac.c and hwif->act_led).
> 
> > 1. The block layer isn't always aware of device activity (eg. flash
> > block erasing in mtd devices) (is this the case for IDE?).
> 
> Same is true for ide-disk changes - they are aware only of filesystem
> activity (no flush cache, special commands, I/O taskfiles etc.).

It wouldn't be too hard to kick the led on DMA start and off after a
timeout kicked from DMA end...

> Isn't ->end_request hook in ide_driver_t enough?
> 
> I see no reason why the custom ->end_request function cannot
> be added to ide-disk.  All needed infrastructure is there.

I'm not sure ide-disk is the right spot ... what if one wants LEDs for
CD-ROMs or other IDE devices like flash cards ?

> > Alternatively it could be made to apply to all ide activity if a
> > suitable start request point was found to hook into.
> 
> start_request() in ide-io.c
> 
> Thanks,
> Bartlomiej