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

[Guenter Roeck]

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@xxxxxx>
> > > > > > ---
> > > > > >   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


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