linux-kernel - Re: [PATCH] serdev: Add ACPI devices by ResourceSource field

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Date:   Mon, 23 Sep 2019 10:14:40 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Maximilian Luz <luzmaximilian@...il.com>
Cc:     Rob Herring <robh@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>, Johan Hovold <johan@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Len Brown <lenb@...nel.org>, linux-serial@...r.kernel.org,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] serdev: Add ACPI devices by ResourceSource field

Hi,

On 23-09-2019 00:29, Maximilian Luz wrote:
> Hi all,
> 
> On 9/20/19 5:00 PM, Hans de Goede wrote:
>> So as promised I've given this patch a try, unfortunately it breaks
>> existing users of ACPI serdev device instantation.
>>
>> After adding this patch "ls /sys/bus/serial/devices" is empty,
>> where as before it gives:
>>
>> [root@...p-45-50 ~]# ls -l /sys/bus/serial/devices/
>> total 0
>> lrwxrwxrwx. 1 root root 0 Sep 20 16:43 serial0 -> ../../../devices/pci0000:00/8086228A:00/serial0
>> lrwxrwxrwx. 1 root root 0 Sep 20 16:43 serial0-0 -> ../../../devices/pci0000:00/8086228A:00/serial0/serial0-0
>>
>> And since the serdev is missing bluetooth does not work.
> 
> Thanks to some testing by Hans, it turns out that the reason for this is
> that acpi_walk_resources fails with AE_AML_INVALID_RESOURCE_TYPE for a
> specific device. If anyone is interested, the _CRS of the device in
> question is
> 
>      Method (_CRS, 0, NotSerialized)  // _CRS: Current Resource Settings
>      {
>          Name (NAM, Buffer (0x14)
>          {
>              "\\_SB.PCI0.SDHB.BRC1"
>          })
>          Name (SPB, Buffer (0x0C)
>          {
>              /* 0000 */  0x8E, 0x1D, 0x00, 0x01, 0x00, 0xC0, 0x02, 0x00,
>              /* 0008 */  0x00, 0x01, 0x00, 0x00
>          })
>          Name (END, ResourceTemplate ()
>          {
>          })
>          Concatenate (SPB, NAM, Local0)
>          Concatenate (Local0, END, Local1)
>          Return (Local1)
>      }
> 
> To solve this, I propose ignoring errors that occur when evaluating the
> _CRS method. Note that with the previously discussed change for v2,
> where we will only look at the first device in _CRS, we should be able
> to handle errors from the actual serdev device allocation separately
> (and only ignore AML evaluation errors).
> 
> Further, I think it might also make sense to move the status and
> already-enumerated checks out of acpi_serdev_register_device to before
> looking at _CRS.

Ack, this is what drivers/i2c/i2c-core-acpi.c is doing and more in general
all ACPI enumeration code always first checks _STA before doing anything
else, so I think it would be best to do this here too.

Actually I think it might be best to fully copy how drivers/i2c/i2c-core-acpi.c
does things.

Regards,

Hans