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From: John Garry <john.garry@huawei.com>
To: Lee Jones <lee.jones@linaro.org>
Cc: Mika Westerberg <mika.westerberg@linux.intel.com>,
	<andriy.shevchenko@linux.intel.com>, <rjw@rjwysocki.net>,
	<linux-acpi@vger.kernel.org>, <lenb@kernel.org>,
	<lorenzo.pieralisi@arm.com>, <linux-kernel@vger.kernel.org>,
	<arnd@arndb.de>, <graeme.gregory@linaro.org>,
	<helgaas@kernel.org>, <linuxarm@huawei.com>,
	<z.liuxinliang@hisilicon.com>,
	"Liguozhu (Kenneth)" <liguozhu@hisilicon.com>
Subject: Re: [RFC PATCH 1/2] ACPI / PNP: Don't add "enumeration_by_parent" devices
Date: Mon, 30 Apr 2018 11:57:55 +0100	[thread overview]
Message-ID: <7dbfc0f9-f03c-c134-82f8-7ef2eba8607c@huawei.com> (raw)
In-Reply-To: <20180430104647.GE5147@dell>

On 30/04/2018 11:46, Lee Jones wrote:
> On Mon, 30 Apr 2018, John Garry wrote:
>
>>>>>> So we using the mfd_cell to match child devices using _HID. At a glance, I
>>>>>> don't actually see other drivers to use mfd_cell_acpi_match.pnpid .
>>>>>>
>>>>>> Anyway we don't use static tables as we need to update the resources of the
>>>>>> cell dynamically. However I do look at a driver like intel_quark_i2c_gpio.c,
>>>>>> and this dynamically modifies the value of global mfd_cell array here:
>>>>>> https://elixir.bootlin.com/linux/latest/source/drivers/mfd/intel_quark_i2c_gpio.c#L266
>>>>>>
>>>>>> I know the cell array is only used at probe time, but this did not look to
>>>>>> be good standard practice to me.
>>>>>
>>>>> Lots of drivers do this to supply dynamic data.  If there is no other
>>>>> sane way of providing such data, it's fine to do.  Although each
>>>>> situation should be dealt with on a case-by-case basis.
>>>>>
>>>>
>>>> Hi Lee,
>>>>
>>>> Thanks for your input.
>>>>
>>>> I do see others drivers which use dynamic mem for the mfd_cells (like
>>>> cros_ec_dev.c), so what we're doing in this driver already is not totally
>>>> unchartered territory. But creating the MFD cells from the ACPI table could
>>>> be ...
>>>
>>> Right.  I don't normally like mixing platform data technologies (MFD,
>>> ACPI and DT).  I normally NACK patches which take information from
>>> Device Tree and populate MFD cells with it.  ACPI would be the same I
>>> guess.
>>
>> Oh, well that is what we have in this driver. So what's the preferred
>> approach? Just not use MFD model at all if ACPI/DT needs to be scanned for
>> data to create the cells?
>
> I've just seen the driver - yuk!
>
> Why are you using the MFD API outside of MFD anyway?

Hi Lee,

This goes back a bit. The original thread was here:
https://lkml.org/lkml/2017/6/13/581

Essentially a method was required to model this host to support platform 
device children for ACPI FW, and this did the job. In hindsight I think 
that there was a misunderstanding in recommending MFD since the devices 
attached are not fixed - hence the dynamic part.

Cheers,
John
>

  reply	other threads:[~2018-04-30 10:58 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-04-20 10:07 [RFC PATCH 0/2] HISI LPC: Add PNP device support John Garry
2018-04-20 10:07 ` [RFC PATCH 1/2] ACPI / PNP: Don't add "enumeration_by_parent" devices John Garry
2018-04-20 13:07   ` Mika Westerberg
2018-04-20 13:24     ` John Garry
2018-04-20 13:52       ` Mika Westerberg
2018-04-20 14:09         ` John Garry
2018-04-26 13:49           ` John Garry
2018-04-26 14:08             ` Mika Westerberg
2018-04-26 14:23               ` John Garry
2018-04-26 14:40                 ` Mika Westerberg
2018-04-27  9:17                 ` John Garry
2018-04-30  5:36                   ` Lee Jones
2018-04-30  9:00                     ` John Garry
2018-04-30  9:26                       ` Lee Jones
2018-04-30  9:35                         ` John Garry
2018-04-30 10:46                           ` Lee Jones
2018-04-30 10:57                             ` John Garry [this message]
2018-04-20 10:07 ` [RFC PATCH 2/2] HISI LPC: Add PNP device support John Garry
2018-04-20 12:50   ` Andy Shevchenko
2018-04-20 13:09     ` John Garry
2018-04-20 13:28       ` Andy Shevchenko
2018-04-20 13:32         ` John Garry
2018-04-20 13:12   ` Mika Westerberg
2018-04-20 13:36     ` John Garry

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