Re: [PATCH] acpi : not caching sun value in acpi_device_pnp

[Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>]

(2014/09/04 6:41), Rafael J. Wysocki wrote:
> On Wednesday, September 03, 2014 01:39:13 PM Yasuaki Ishimatsu wrote:
>> By this commit, "202317a : ACPI / scan: Add acpi_device objects for all
>> device nodes in the namespace", all device nodes in the namespace are
>> shown under /sys/bus/acpi/devices directory even if the devices are not
>> present and not functional. And if a device node has _SUN method, it is
>> decoded and the sun value is cached to acpi_device_pnp->sun.
>>
>> But when device is not present and not functional, some firmware returns
>> wrong sun value. And the wrong value is cached to acpi_device_pnp->sun.
>>
>> Therefore, even if a device is hot added and firmware returns correct
>> sun value of the device, the value is not reflected to
>> acpi_device_pnp->sun. So user cannot know correct sun value of the
>> device.
>>
>> By not caching sun value, the patch fixes the issue.
>

> Queued up for 3.17-rc4, but with a different changelog, because in my opinion
> the main problem is that _SUN is not guaranteed to return the same value
> every time it is evaluated, so either it should not be cached, or we should
> update the cached value whenever the device status changes.

I see. I have no objection to changing the changelog.
Please change it.

Thanks,
Yasuaki Ishimatsu
>
>> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
>> Suggested-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>> ---
>>    drivers/acpi/scan.c     | 15 ++++++++-------
>>    include/acpi/acpi_bus.h |  1 -
>>    2 files changed, 8 insertions(+), 8 deletions(-)
>>
>> diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
>> index 9a92989..3bf7764 100644
>> --- a/drivers/acpi/scan.c
>> +++ b/drivers/acpi/scan.c
>> @@ -667,8 +667,14 @@ static ssize_t
>>    acpi_device_sun_show(struct device *dev, struct device_attribute *attr,
>>    		     char *buf) {
>>    	struct acpi_device *acpi_dev = to_acpi_device(dev);
>> +	acpi_status status;
>> +	unsigned long long sun;
>> +
>> +	status = acpi_evaluate_integer(acpi_dev->handle, "_SUN", NULL, &sun);
>> +	if (ACPI_FAILURE(status))
>> +		return -ENODEV;
>>
>> -	return sprintf(buf, "%lu\n", acpi_dev->pnp.sun);
>> +	return sprintf(buf, "%llu\n", sun);
>>    }
>>    static DEVICE_ATTR(sun, 0444, acpi_device_sun_show, NULL);
>>
>> @@ -690,7 +696,6 @@ static int acpi_device_setup_files(struct acpi_device *dev)
>>    {
>>    	struct acpi_buffer buffer = {ACPI_ALLOCATE_BUFFER, NULL};
>>    	acpi_status status;
>> -	unsigned long long sun;
>>    	int result = 0;
>>
>>    	/*
>> @@ -731,14 +736,10 @@ static int acpi_device_setup_files(struct acpi_device *dev)
>>    	if (dev->pnp.unique_id)
>>    		result = device_create_file(&dev->dev, &dev_attr_uid);
>>
>> -	status = acpi_evaluate_integer(dev->handle, "_SUN", NULL, &sun);
>> -	if (ACPI_SUCCESS(status)) {
>> -		dev->pnp.sun = (unsigned long)sun;
>> +	if (acpi_has_method(dev->handle, "_SUN")) {
>>    		result = device_create_file(&dev->dev, &dev_attr_sun);
>>    		if (result)
>>    			goto end;
>> -	} else {
>> -		dev->pnp.sun = (unsigned long)-1;
>>    	}
>>
>>    	if (acpi_has_method(dev->handle, "_STA")) {
>> diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
>> index bcfd808..c1c9de1 100644
>> --- a/include/acpi/acpi_bus.h
>> +++ b/include/acpi/acpi_bus.h
>> @@ -246,7 +246,6 @@ struct acpi_device_pnp {
>>    	acpi_device_name device_name;	/* Driver-determined */
>>    	acpi_device_class device_class;	/*        "          */
>>    	union acpi_object *str_obj;	/* unicode string for _STR method */
>> -	unsigned long sun;		/* _SUN */
>>    };
>>
>>    #define acpi_device_bid(d)	((d)->pnp.bus_id)
>>
>>
>> --
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>