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 13:51:59 +0200
From:	Andreas Werner <andreas.werner@....de>
To:	Lee Jones <lee.jones@...aro.org>
CC:	Johannes Thumshirn <johannes.thumshirn@....de>,
	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

aOn Wed, May 28, 2014 at 09:24:05AM +0100, Lee Jones wrote:
> > > > 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'?
>

I think it was a missunderstanding. I also thought that i just
have to adapt the wrapper to the original API, that is what I did in the patch,
and not to delete the functions completly.

Anayway, we currently have another project which use a STM32 MCR connected to USB.
A nice feature of this STM is to update the firmware using the USB interface.
This is easy to implement and fast.

We want to use such a functionality in all of our MCRs to easily update the firmware
at the customer if we found a bug.

We also plan to have a BMC connected to USB. Then we have i2c and USB.

Regards
Andy

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