linux-kernel - Re: [lm-sensors] [PATCH] hwmon: (max6650) Rename the device ids to contain the hwmon suffix

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Message-ID: <CAOMwXhNr27fwwhr=Fb996b1DtSb0R6xiasMY2PsbTwVNe2qgOQ@mail.gmail.com>
Date:	Mon, 10 Feb 2014 17:06:46 +0000
From:	Laszlo Papp <lpapp@....org>
To:	Jean Delvare <jdelvare@...e.de>
Cc:	Lee Jones <lee.jones@...aro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Guenter Roeck <linux@...ck-us.net>, lm-sensors@...sensors.org
Subject: Re: [lm-sensors] [PATCH] hwmon: (max6650) Rename the device ids to
 contain the hwmon suffix

On Mon, Feb 10, 2014 at 4:38 PM, Jean Delvare <jdelvare@...e.de> wrote:
> Hi Lee, Laszlo,
>
> On Mon, 10 Feb 2014 16:08:42 +0000, Lee Jones wrote:
>> > In the preparation of creating an mfd driver and then refactor this one into a
>> > platform driver in order to add some pinctrl functionality to the chip, it is
>> > necessary to start the series with this change so that the mfd driver can refer
>> > to the proper name in the subsequent change without making changes in more than
>> > one driver later.
>> >
>> > This was a request from Lee Jones, the MFD subsystem maintainer.
>> >
>> > Signed-off-by: Laszlo Papp <lpapp@....org>
>> > ---
>> >  drivers/hwmon/max6650.c | 4 ++--
>> >  1 file changed, 2 insertions(+), 2 deletions(-)
>> >
>> > diff --git a/drivers/hwmon/max6650.c b/drivers/hwmon/max6650.c
>> > index 0cafc39..3c36edc 100644
>> > --- a/drivers/hwmon/max6650.c
>> > +++ b/drivers/hwmon/max6650.c
>> > @@ -116,8 +116,8 @@ static struct max6650_data *max6650_update_device(struct device *dev);
>> >   */
>> >
>> >  static const struct i2c_device_id max6650_id[] = {
>> > -   { "max6650", 1 },
>> > -   { "max6651", 4 },
>> > +   { "max6650-hwmon", 1 },
>> > +   { "max6651-hwmon", 4 },
>
> No, this is not acceptable, sorry. This will change the name of the
> hwmon device as seen from user-space, breaking any configuration file
> referring to it. Additionally, dashes are explicitly forbidden in hwmon
> device names. And lastly this will break any explicit instantiation of
> theses devices (which is the only way, as the driver doesn't support
> device auto-detection), be it in the kernel itself or from user-space.
>
> The change doesn't make sense anyway. If you move to the MFD framework,
> the core driver will be an I2C driver binding to the I2C device, and it
> will spawn the logical devices, presumably in the form of platform
> devices. That's what the current max6650 driver would have to bind to.
> Just renaming the device won't work, you also need to change the type.

Hmm, this paragraph seems to indicate that you have not seen my
previous patch set. I tried to summarize in this commit message that
the type in this subdriver would need to change, yes.

I am fine with not renaming, but appending if such a thing is
possible. What does not make sense to me is acquiring a "global"
max665x name in a sub-device driver. The children have to be
distinguished somehow!

> If you want to turn this into an MFD driver, I believe you must first
> convert the hwmon part to register using
> devm_hwmon_device_register_with_groups(). This will dissociate the i2c
> device name from the hwmon device name and create a clean name-space
> for each function. Guenter, maybe you had a plan to do so already
> anyway?
>
> That being said, going with MFD in this case seems quite overkill to
> me. MFD makes a lot of sense when each function has its own resources.
> As this isn't the case here, a single driver registering both an hwmon
> interface and a pinctrl interface would seem sufficient to me. But I
> think Guenter already discussed this in the past so I'll let him
> continue and decide.

Exactly. This had been overdiscussed. I took my personal preference
without any technical drawback. I prefer clean separation just like
several other mfd drivers are doing, really.

Tell me this is unacceptable, and I will stop helping with getting the
required functionality into the kernel. Frankly, I am getting tired of
having worked on it for a few months now, and we are still at
discussing personal preferences rather than getting features in ...
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