From: John Garry <john.garry@huawei.com>
To: Olof Johansson <olof@lixom.net>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <lenb@kernel.org>,
"jeremy.linton@arm.com" <jeremy.linton@arm.com>,
Arnd Bergmann <arnd@arndb.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"linux-acpi@vger.kernel.org" <linux-acpi@vger.kernel.org>,
"Guohanjun (Hanjun Guo)" <guohanjun@huawei.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [PATCH RFC 2/2] soc: Add a basic ACPI generic driver
Date: Wed, 29 Jan 2020 09:58:04 +0000 [thread overview]
Message-ID: <734a01d8-3b50-48ca-1d94-d79d0e6610ff@huawei.com> (raw)
In-Reply-To: <CAOesGMjrC=b781LLU-Btp1b9uKTiMXj8tF3rjK_Wy6Q4iaR+Rw@mail.gmail.com>
Hi Olof,
>>>
>>> Based on everything I've seen so far, this should go under drivers/acpi instead.
>>
>> soc drivers seem to live in drivers/soc (non-arm32, anyway), so I
>> decided on this location. But drivers/acpi would also seem reasonable now.
>
> We don't want drivers/soc to be too much of a catch-all -- it is meant
> for some of the glue pieces that don't have good homes elsewhere.
> Unfortunately, the slope is slippery and we've already gone down it a
> bit, but I think we can fairly clearly declare that this kind of
> cross-soc material is likely not the right home for it -- especially
> when drivers/acpi is a good fit in this case.
ok
>
>>>> diff --git a/drivers/soc/acpi_generic.c b/drivers/soc/acpi_generic.c
>>>> new file mode 100644
>>>> index 000000000000..34a1f5f8e063
>>>> --- /dev/null
>>>> +++ b/drivers/soc/acpi_generic.c
>>>> @@ -0,0 +1,102 @@
>>>> +// SPDX-License-Identifier: GPL-2.0
>>>> +/*
>>>> + * Copyright (c) John Garry, john.garry@huawei.com
>>>> + */
>>>> +
>>>> +#define pr_fmt(fmt) "SOC ACPI GENERIC: " fmt
>>>> +
>>>> +#include <linux/acpi.h>
>>>> +#include <linux/sys_soc.h>
>>>> +
[...]
>>>
>>> Hmm, this doesn't look like much of a driver to me. This looks like
>>> the export of an attribute to userspace, and should probably be done
>>> by ACPI core instead of creating an empty driver for it.
>>
>> OK, but I'm thinking that having a soc driver can be useful as it is
>> common to DT, and so userspace only has to check a single location. And
>> the soc driver can also cover multiple-chip systems without have to
>> reinvent that code for ACPI core. And it saves adding a new ABI.
>
> While having a single location could be convenient, the actual data
> read/written would be different (I'm guessing).
Without doubt we would have different data sometimes between ACPI and DT
FW..
And it is not ideal that the soc_id sysfs file could have different
contents for the same SoC, depending on ACPI or DT.
>
> We also already have a supposed standard way of figuring out what SoC
> we're on (toplevel compatible for the DT).
From checking some soc drivers, there is a distinction between how
soc_id and machine is evaluated: machine comes from DT model, which
looks standard; however soc_id seems to have different methods of
evaluate, like sometimes reading some system id register (I'm checking
exynos-chipid.c there).
We're just looking for soc_id. But, as before, it would probably be
different between ACPI and DT, so not ideal.
So no matter what, I think
> userspace will need to handle two ways of probing this.
>
That should not be a big problem.
>
Thanks,
John
next prev parent reply other threads:[~2020-01-29 9:58 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-28 11:14 [PATCH RFC 0/2] Add basic generic ACPI soc driver John Garry
2020-01-28 11:14 ` [PATCH RFC 1/2] ACPI/PPTT: Add acpi_pptt_get_package_info() API John Garry
2020-01-28 12:34 ` Sudeep Holla
2020-01-28 14:04 ` John Garry
2020-01-28 14:54 ` Sudeep Holla
2020-01-29 11:03 ` John Garry
2020-01-30 11:23 ` Sudeep Holla
2020-01-30 16:12 ` John Garry
2020-01-30 17:41 ` Sudeep Holla
2020-01-31 10:58 ` John Garry
2020-01-28 11:14 ` [PATCH RFC 2/2] soc: Add a basic ACPI generic driver John Garry
2020-01-28 11:56 ` Greg KH
2020-01-28 13:33 ` John Garry
2020-01-28 12:50 ` Arnd Bergmann
2020-01-28 14:46 ` John Garry
2020-01-28 15:20 ` Sudeep Holla
2020-01-28 15:59 ` John Garry
2020-01-28 16:17 ` Sudeep Holla
2020-01-28 17:51 ` Olof Johansson
2020-01-28 18:22 ` John Garry
2020-01-28 19:11 ` Rafael J. Wysocki
2020-01-28 19:28 ` John Garry
2020-01-28 22:30 ` Rafael J. Wysocki
2020-01-29 10:27 ` John Garry
2020-01-28 20:06 ` Olof Johansson
2020-01-29 9:58 ` John Garry [this message]
2020-01-28 16:56 ` [PATCH RFC 0/2] Add basic generic ACPI soc driver Jeremy Linton
2020-01-28 17:28 ` John Garry
2020-01-28 19:04 ` Jeremy Linton
2020-01-28 20:07 ` John Garry
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