linux-kernel - Re: [PATCH RFC 2/2] soc: Add a basic ACPI generic driver

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Date:   Wed, 29 Jan 2020 10:27:30 +0000
From:   John Garry <john.garry@...wei.com>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
CC:     Olof Johansson <olof@...om.net>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>,
        Jeremy Linton <jeremy.linton@....com>,
        "Arnd Bergmann" <arnd@...db.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Hanjun Guo <guohanjun@...wei.com>,
        "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Subject: Re: [PATCH RFC 2/2] soc: Add a basic ACPI generic driver

>>
>>> Any reasons for not putting it into drivers/acpi/pptt.c specifically?
>>> .
>>
>> I don't think so.
>>
>> One thing is that the code does a one-time scan of the PPTT to find all
>> processor package nodes with ID structures to register the soc devices -
>> so we would need some new call from from acpi_init() for that.
> 

Hi Rafael,

 > Or an extra initcall or similar. [Calls from acpi_init() are basically
 > for things that need to be strictly ordered in a specific way for some
 > reason.]>
 > Why would that be a problem?

I don't see a problem if we want to use a soc driver, but that is 
starting to look unlikely.

Alternatively, if we want to create some folder under 
/sys/firmware/acpi, any restriction comes from the folder location.

For a folder like /sys/firmware/acpi/pptt, we need to ensure acpi_kobj 
is initialized; acpi_kobj is set from subsys_init(acpi_init), so 
module_init() for pptt module would suffice.

However if we wanted to make pptt folder a sub-folder from those created 
in acpi_sysfs_init() - then we would need to make that parent folder 
kobj non-static. Again, module_init() would suffice.

Thanks,
John