linux-kernel - Re: [PATCH v3 2/8] mfd / platform: cros_ec: move lightbar attributes to its own driver.

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Message-ID: <20181204092121.GR26661@dell>
Date:   Tue, 4 Dec 2018 09:21:21 +0000
From:   Lee Jones <lee.jones@...aro.org>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     gwendal@...omium.org, drinkcat@...omium.org,
        linux-kernel@...r.kernel.org, groeck@...omium.org,
        kernel@...labora.com, bleung@...omium.org,
        Olof Johansson <olof@...om.net>
Subject: Re: [PATCH v3 2/8] mfd / platform: cros_ec: move lightbar attributes
 to its own driver.

On Mon, 03 Dec 2018, Enric Balletbo i Serra wrote:
> On 3/12/18 11:36, Lee Jones wrote:
> > On Tue, 27 Nov 2018, Enric Balletbo i Serra wrote:
> > 
> >> The entire way how cros sysfs attibutes are created is broken.
> >> cros_ec_lightbar should be its own driver and its attributes should be
> >> associated with a lightbar driver not the mfd driver. In order to retain
> >> the path, the lightbar attributes are attached to the cros_class.
> > 
> > I'm not exactly clear on what a lightbar is, but shouldn't it live in
> > the appropriate subsystem.  Like LED for example?
> > 
> 
> The lightbar is a four-color indicator available on some Chromebook, but the
> fact that can you can program this lightbar with different sequences, including
> user defined sequences makes the device a bit special and very chrome platform
> specific. The same happens with the VBC driver.

Being Chrome specific doesn't necessarily mean that these drivers
shouldn't reside in a proper subsystem.  A lot of drivers in the
kernel are only relevant to very specific hardware/platforms.

IMHO code in drivers/platform should pertain only to the core platform
itself.  Any drivers for leaf hardware/functionality should be split
out into the subsystems, however niche you think they are.

I also understand the convenience factor of not having to go through
a !Google Maintainer, but this is not a loophole I'm prepared to
support. ;)

> Other subdevices like, rtc, keyboard, usbpd charger,etc. are already in their
> subsystems.
> 
> >> The patch also adds the sysfs documentation.
> >>
> >> Signed-off-by: Enric Balletbo i Serra <enric.balletbo@...labora.com>
> >> ---
> >>
> >> Changes in v3:
> >> - Removed unneded check for ec_dev.
> >>
> >> Changes in v2:
> >> - Removed the two exported functions to attach/detach to the cros_class.
> >> - Use dev_warn instead of dev_err when adding the lightbar.
> >>
> >>  ...sfs-class-chromeos-driver-cros-ec-lightbar | 74 +++++++++++++++
> >>  drivers/mfd/cros_ec_dev.c                     | 24 ++---
> >>  drivers/mfd/cros_ec_dev.h                     |  6 --
> >>  drivers/platform/chrome/Kconfig               | 10 ++
> >>  drivers/platform/chrome/Makefile              |  3 +-
> >>  drivers/platform/chrome/cros_ec_lightbar.c    | 95 ++++++++++++++-----
> >>  include/linux/mfd/cros_ec.h                   |  1 -
> >>  7 files changed, 172 insertions(+), 41 deletions(-)
> >>  create mode 100644 Documentation/ABI/testing/sysfs-class-chromeos-driver-cros-ec-lightbar
> > 

-- 
Lee Jones [李琼斯]
Linaro Services Technical Lead
Linaro.org │ Open source software for ARM SoCs
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