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

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Date:	Mon, 2 Jun 2014 10:06:36 +0200
From:	Andreas Werner <andreas.werner@....de>
To:	Guenter Roeck <linux@...ck-us.net>
CC:	Andreas Werner <andreas.werner@....de>,
	Lee Jones <lee.jones@...aro.org>,
	Johannes Thumshirn <johannes.thumshirn@....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

On Wed, May 28, 2014 at 06:52:56AM -0700, Guenter Roeck wrote:
> On 05/28/2014 06:29 AM, Guenter Roeck wrote:
> >On 05/28/2014 04:51 AM, Andreas Werner wrote:
> >>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.
> >>
> >
> >Even more likely that you would have to change the API in that case to be less
> >I2C centric.
> >
> 
> ... especially since you have "struct i2c_client *client" in your API function.
> 
> Guenter
> 
> 
Ok I agree. I will change that and delete the wrapper functions completley.
I will prepare and send a v3.

Thanks for the discussion.

Regards
Andy
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