linux-kernel - Re: [PATCH 5/5] firmware: add DECLARE_FW_CUSTOM

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Date:   Wed, 21 Dec 2016 19:49:02 +0100
From:   Pavel Machek <pavel@....cz>
To:     Jacek Anaszewski <jacek.anaszewski@...il.com>
Cc:     Milo Kim <woogyom.kim@...il.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>,
        gregkh@...uxfoundation.org, ming.lei@...onical.com,
        daniel.wagner@...-carit.de, teg@...m.no, mchehab@....samsung.com,
        zajec5@...il.com, linux-kernel@...r.kernel.org,
        markivx@...eaurora.org, stephen.boyd@...aro.org,
        broonie@...nel.org, zohar@...ux.vnet.ibm.com, tiwai@...e.de,
        johannes@...solutions.net, chunkeey@...glemail.com,
        hauke@...ke-m.de, jwboyer@...oraproject.org,
        dmitry.torokhov@...il.com, dwmw2@...radead.org, jslaby@...e.com,
        torvalds@...ux-foundation.org, luto@...capital.net,
        fengguang.wu@...el.com, rpurdie@...ys.net,
        j.anaszewski@...sung.com, Abhay_Salunke@...l.com,
        Julia.Lawall@...6.fr, Gilles.Muller@...6.fr, nicolas.palix@...g.fr,
        dhowells@...hat.com, bjorn.andersson@...aro.org,
        arend.vanspriel@...adcom.com, kvalo@...eaurora.org,
        linux-leds@...r.kernel.org
Subject: Re: [PATCH 5/5] firmware: add DECLARE_FW_CUSTOM_FALLBACK() annotation

Hi!

> >>> Milo if sysfs is used can't the old userspace be mapped to use the new
> >>> sysfs interface through a wrapper of some sort ? What exactly would be
> >>> needed to ensure old userspace will not break?
> >>
> >> LP5521 and LP5523 have two ways to load hex code from the userspace - the
> >> sysfs and firmware I/F. So user program supports both interfaces. Even if
> >> the firmware I/F is not available, user can still run LED effect through the
> >> sysfs.
> >>
> >> However, LP5562 and LP8501 support only single way which is the firmware
> >> I/F. So user-space program for LP5562/8501 should be modified if lp55xx
> >> removes the interface. My idea is
> > 
> > Actually... it would be good to have some reasonable interface for RGB
> > LEDs. This way, we need separate "firmware" for each LED
> > controller. It would be good to have common format for LED effects.
> 
> We still haven't tried trigger approach discussed over half a year ago.
> If we used firmware approach we would still have to overcome the problem
> of defining the LED class drivers affected by the firmware program.

The firmware approach is in the tree today :-(.

> >> Device manufactures in Asia & North America requested lp55xx drivers, but I
> >> don't know how many vendors uses the firmware I/F. Some vendors embeds the
> >> binary code inside the driver instead of using user-program.
> > 
> > Nokia N900 uses lp55xx, and I have custom scripts interfacing sysfs.
> > 
> > Maemo uses the LEDs, too, but maemo is not open source.
> > 
> > So no, I don't think there's anything important that could be broken.
> 
> We can't guarantee that. Is there any problem in just using the
> currently introduced DECLARE_FW_CUSTOM_FALLBACK() in
> drivers/leds/leds-lp55xx-common.c?

Well, it would be good to get rid of the custom fallback
functionality. And no, we don't need to "guarantee" that.  Removing
obscure functionality noone uses is far game... providing noone
complains ;-).

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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