linux-kernel - Re: [RFC PATCH 1/2] ACPI / PNP: Don't add "enumeration_by

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Message-ID: <44e047a2-93e1-9eff-45b8-d538a7ae9092@huawei.com>
Date:   Fri, 27 Apr 2018 10:17:45 +0100
From:   John Garry <john.garry@...wei.com>
To:     Mika Westerberg <mika.westerberg@...ux.intel.com>
CC:     <andriy.shevchenko@...ux.intel.com>, <rjw@...ysocki.net>,
        <linux-acpi@...r.kernel.org>, <lenb@...nel.org>,
        <lorenzo.pieralisi@....com>, <linux-kernel@...r.kernel.org>,
        <arnd@...db.de>, <graeme.gregory@...aro.org>, <helgaas@...nel.org>,
        <linuxarm@...wei.com>, <z.liuxinliang@...ilicon.com>,
        "Liguozhu (Kenneth)" <liguozhu@...ilicon.com>,
        <lee.jones@...aro.org>
Subject: Re: [RFC PATCH 1/2] ACPI / PNP: Don't add "enumeration_by_parent"
 devices

On 26/04/2018 15:23, John Garry wrote:

+

> On 26/04/2018 15:08, Mika Westerberg wrote:
>> On Thu, Apr 26, 2018 at 02:49:49PM +0100, John Garry wrote:
>>> diff --git a/drivers/bus/hisi_lpc.c b/drivers/bus/hisi_lpc.c
>>> index 2d4611e..b04425b 100644
>>> --- a/drivers/bus/hisi_lpc.c
>>> +++ b/drivers/bus/hisi_lpc.c
>>> @@ -18,6 +18,8 @@
>>>  #include <linux/of_platform.h>
>>>  #include <linux/pci.h>
>>>  #include <linux/slab.h>
>>> +#include <linux/serial_8250.h>
>>> +#include "../tty/serial/8250/8250.h"
>>>
>>>  #define DRV_NAME "hisi-lpc"
>>>
>>> @@ -345,6 +347,7 @@ static void hisi_lpc_comm_outs(void *hostdata,
>>> unsigned
>>> long pio,
>>>  #define MFD_CHILD_NAME_LEN (ACPI_ID_LEN +
>>> sizeof(MFD_CHILD_NAME_PREFIX) -
>>> 1)
>>>
>>>  struct hisi_lpc_mfd_cell {
>>> +    struct plat_serial8250_port serial8250_port;
>>>      struct mfd_cell_acpi_match acpi_match;
>>>      char name[MFD_CHILD_NAME_LEN];
>>>      char pnpid[ACPI_ID_LEN];
>>> @@ -513,10 +516,31 @@ static int hisi_lpc_acpi_probe(struct device
>>> *hostdev)
>>>          dev_warn(&child->dev, "set resource fail (%d)\n", ret);
>>>              return ret;
>>>          }
>>> +    if (!strcmp(acpi_device_hid(child), "HISI1031")) {
>>
>
> Hi Mika,
>
>> Hmm, there is a way in struct mfd_cell to match child devices using _HID
>> so is there something preventing you from using that?
>
> Not that I know about. Can you describe this method? I guess I also
> don't need to set the mfd_cell pnpid either for this special case device.
>

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.

Thanks,
John

> Thanks,
> John
>
>
>>
>> .
>>
>