Re: [PATCH v4 1/2] Bluetooth: Add device_get_bd_address()

From: Pavel Machek <pavel@ucw.cz>
To: Marcel Holtmann <marcel@holtmann.org>
Cc: Matthias Kaehlcke <mka@chromium.org>,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Sinan Kaya <okaya@codeaurora.org>,
	Balakrishna Godavarthi <bgodavar@codeaurora.org>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	Marcin Wojtas <mw@semihalf.com>,
	Andy Shevchenko Andy Shevchenko <andy.shevchenko@gmail.com>,
	Johan Hedberg <johan.hedberg@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Bluez mailing list <linux-bluetooth@vger.kernel.org>,
	Loic Poulain <loic.poulain@linaro.org>,
	Brian Norris <briannorris@chromium.org>
Subject: Re: [PATCH v4 1/2] Bluetooth: Add device_get_bd_address()
Date: Mon, 22 Oct 2018 23:07:07 +0200	[thread overview]
Message-ID: <20181022210707.GA3764@amd> (raw)
In-Reply-To: <8D254888-52A9-4201-882C-EDE71EE4CF5C@holtmann.org>

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Hi!

> >> explain to me again why this is useful?
> > 
> > The official binding for providing the BD_ADDR through the device tree
> > is the property 'local-bd-address'. device_get_bd_address() provides a
> > common API to retrieve the BD_ADDR instead of requiring BT drivers to
> > use the lower level fwnode_property_read_u8_array(). It also avoids
> > repeating the check for an all zeroes BD_ADDR in multiple drivers.
> > 
> >> I am failing to see the benefit if this is not part of the property.h API.
> > 
> > My understanding is that the intention of property.h it to provide an
> > API for common property types used by drivers from different
> > subsystems, hence the implementation 'lives' in drivers/base.
> > Obtaining the BD_ADDR is clearly limited to the Bluetooth subsystem,
> > and drivers/base doesn't seem to be the right place for it. It's true,
> > device_get_mac_address() lives in the common property code, but that
> > doesn't necessarily mean it really should be there and we should do
> > the same. I agree with Sakari that the the approach taken by V4L2
> > (drivers/media/v4l2-core/v4l2-fwnode.c) seems more appropriate.
> > 
> > That said I wouldn't raise opposition if the maintainers of
> > drivers/base agreed to add device_get_mac_address() there, however so
> > far several recent authors of property.[ch] have raised objections.
> 
> so if this is not in drivers/base/ then what is the point in making each driver do this? If it is a common property, then it can be well handled in the Bluetooth core when setting up the hardware.
> 
> This whole BD_ADDR via DT is stupid anyway. Just so that is clear
> up-front. It has been a total hack and fully relies on boot
> loaders doing too much magic and then using DT to hide this magic.

Can you wrap lines at around 72 characters in the emails?

We do ethernet addresses via DT. I don't know if doing that in
bootloader is a hack or not, but if bootloader is already doing that
for ethernet, bluettoth address in DT kind of makes sense.

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

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