linux-kernel - Re: [PATCH PoC 1/3] ACPI / PNP: Don't add enumeration_by

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Message-ID: <366fd6dd-a37b-c7ec-fdf3-48f8a8024834@huawei.com>
Date:   Fri, 19 Aug 2022 09:05:32 +0100
From:   John Garry <john.garry@...wei.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
CC:     Len Brown <lenb@...nel.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        "ACPI Devel Maling List" <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linuxarm <linuxarm@...wei.com>
Subject: Re: [PATCH PoC 1/3] ACPI / PNP: Don't add enumeration_by_parent
 devices

On 18/08/2022 20:31, Andy Shevchenko wrote:
>> For the  hisi_lpc driver, for the UART ACPI node we have a binding like:
>>
>>   Device (LPC0.CON0) {
>>      Name (_HID, "HISI1031")
>>      Name (_CID, "PNP0501")
>>      Name (LORS, ResourceTemplate() {
>>        QWordIO (
>>
>> We have the compat and hid string. The ACPI/PNP code matches the compat
>> string first, and creates the PNP device. In doing so, the acpi_device
>> created has physical_node_count member set in acpi_bind_one().
>>
>> The hisi_lpc driver also creates a platform device serial device for uart,
>> which is the actual uart which we want to use - see
>> hisi_lpc_acpi_add_child(). That function does not check
>> physical_node_count value, but acpi_create_platform_device() does check it.
>> So if we were to move hisi_lpc_acpi_add_child() across to use
>> acpi_create_platform_device(), then the change in this patch is required to
>> not create the PNP binding (so that physical_node_count is not set from
>> PNP probe).
> Hmm... The flag, as I interpret it, is equal to "the device in
> question is a peripheral device to the non-discoverable bus, such as
> SPI, I2C or UART". I.o.w. I do not see how PNP suits here. So, from my
> point of view it seems like an abuse of the flag. Not sure the current
> state of affairs in ACPI glue layer regarding this, though.

Hi Andy,

Sorry, but I'm not following you here. Which flag are you talking about?

thanks,
John