linux-kernel - Re: [PATCH v2 1/3] drivers/mfd/menf21bmc: introduce MEN 14F021P00 BMC MFD Core driver

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Date:	Wed, 28 May 2014 09:24:05 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Johannes Thumshirn <johannes.thumshirn@....de>
Cc:	Andreas Werner <andreas.werner@....de>,
	linux-kernel@...r.kernel.org, sameo@...ux.intel.com, wim@...ana.be,
	linux-watchdog@...r.kernel.org, cooloney@...il.com,
	rpurdie@...ys.net, linux-leds@...r.kernel.org
Subject: Re: [PATCH v2 1/3] drivers/mfd/menf21bmc: introduce MEN 14F021P00
 BMC MFD Core driver

> > > The MEN 14F021P00 Board Management Controller provides an
> > > I2C interface to the host to access the feature implemented in the BMC.
> > > The BMC is a PIC Microntroller assembled on CPCI Card from MEN Mikroelektronik
> > > and on a few Box/Display Computer.
> > >
> > > Added MFD Core driver, supporting the I2C communication to the device.
> > >
> > > The MFD driver currently supports the following features:
> > > 	- Watchdog
> > > 	- LEDs
> > >
> > > Signed-off-by: Andreas Werner <andreas.werner@....de>
> > > ---
> > >  drivers/mfd/Kconfig           |  12 +++
> > >  drivers/mfd/Makefile          |   1 +
> > >  drivers/mfd/menf21bmc.c       | 220 ++++++++++++++++++++++++++++++++++++++++++
> > >  include/linux/mfd/menf21bmc.h |  31 ++++++
> > >  4 files changed, 264 insertions(+)
> > >  create mode 100644 drivers/mfd/menf21bmc.c
> > >  create mode 100644 include/linux/mfd/menf21bmc.h

[...]

> > > +static int menf21bmc_write_byte(struct i2c_client *client, u8 val)
> > > +{
> > > +	int ret;
> > > +	struct menf21bmc *data = i2c_get_clientdata(client);
> > > +
> > > +	mutex_lock(&data->lock);
> > > +	ret = i2c_smbus_write_byte(client, val);
> > > +	mutex_unlock(&data->lock);
> > > +
> > > +	return ret;
> > > +}
> >
> > Didn't we ask you to remove these?  Just make the i2c_smbus_* calls
> > from within the driver.  The I2C subsystem conducts its own locking.
> > I'm really starting to frown on aggregation for the sake of
> > aggregation.  It's just overhead.
> >
> 
> Correct me if I'm wrong but as far as I remember Guenther asked to retain the
> original API, not the remove the "abstraction layer". Once we build a board with
> one of these BMCs attached via e.g. SPI we would have to reintroduce it anyways,
> in order to re-use these drivers.

If there are two or more possible interfaces then I agree, these
aggregations would be the best approach.  However, as it stands, that's
not currently the case.

Genuine question; are Men on the verge of building such a board, or
are we talking about 'ifs' and 'maybes'?

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
Follow Linaro: Facebook | Twitter | Blog
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