linux-kernel - Re: [PATCH v2] iio: light: acpi-als: Properly enable on ASUS Zenbooks

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Date:   Thu, 19 Jan 2017 17:27:20 +0100
From:   Marek Vasut <marex@...x.de>
To:     atx@....name, linux-iio@...r.kernel.org
Cc:     jic23@...nel.org, knaack.h@....de, lars@...afoo.de,
        pmeerw@...erw.net, maitysanchayan@...il.com,
        gregor.boirie@...rot.com, linux-kernel@...r.kernel.org,
        rui.zhang@...el.com, marxin.liska@...il.com
Subject: Re: [PATCH v2] iio: light: acpi-als: Properly enable on ASUS Zenbooks

On 01/19/2017 05:19 PM, atx@....name wrote:
> January 19 2017 4:49 PM, "Marek Vasut" <marex@...x.de> wrote:
>> On 01/19/2017 12:48 PM, Josef Gajdusek wrote:
>>
>>> ASUS Zenbooks need several special ACPI calls to enable the ALS peripheral.
>>> Otherwise, reads just return 0.
>>>
>>> Signed-off-by: Josef Gajdusek <atx@....name>
>>> ---
>>> drivers/iio/light/acpi-als.c | 17 +++++++++++++++++
>>> 1 file changed, 17 insertions(+)
>>>
>>> diff --git a/drivers/iio/light/acpi-als.c b/drivers/iio/light/acpi-als.c
>>> index f0b47c5..ccd5787 100644
>>> --- a/drivers/iio/light/acpi-als.c
>>> +++ b/drivers/iio/light/acpi-als.c
>>> @@ -39,6 +39,9 @@
>>> #define ACPI_ALS_DEVICE_NAME "acpi-als"
>>> #define ACPI_ALS_NOTIFY_ILLUMINANCE 0x80
>>>
>>> +#define ACPI_ALS_ASUS_TALS "\\_SB.PCI0.LPCB.EC0.TALS"
>>> +#define ACPI_ALS_ASUS_ALSC "\\_SB.ATKD.ALSC"
>>> +
>>> ACPI_MODULE_NAME("acpi-als");
>>>
>>> /*
>>> @@ -170,6 +173,16 @@ static int acpi_als_read_raw(struct iio_dev *indio_dev,
>>> return IIO_VAL_INT;
>>> }
>>>
>>> +static void acpi_als_quirk_asus(struct acpi_als *als)
>>> +{
>>> + acpi_execute_simple_method(NULL, ACPI_ALS_ASUS_TALS, 1);
>>> + acpi_execute_simple_method(NULL, ACPI_ALS_ASUS_ALSC, 1);
>>
>> This will run on ALL systems, right ? Also, error checking disappeared ?
>>
> 
> Yes, that's intended. Should I add some DMI checks to only run on
> ASUS/ASUS Zenbooks?

Definitely, it doesn't seem right to execute random stuff on hardware
where such stuff is undefined.

> As for error checking, this code behaves exactly like v1, except
> that the xor warning is removed, which means that it is not needed
> to explicitly get the handles. The acpi_exceute_simple_method call just
> fails if it can't find the object.

But the driver will register even though the call fails , that's wrong.
The probe must stop if there is a failure.

> Distinguishing between the "object not found" and "failed to call method" scenarios
> seemed a bit overly verbose to me especially as it would probably be overkill to abort
> the driver initialization because of that.

If something which should be present (like the acpi method) is not
present and/or fails, the driver probe should abort.

>>> +}
>>> +
>>> +static void (*acpi_als_quirks[])(struct acpi_als *als) = {
>>> + acpi_als_quirk_asus,
>>> +};
>>> +
>>> static const struct iio_info acpi_als_info = {
>>> .driver_module = THIS_MODULE,
>>> .read_raw = acpi_als_read_raw,
>>> @@ -180,6 +193,7 @@ static int acpi_als_add(struct acpi_device *device)
>>> struct acpi_als *als;
>>> struct iio_dev *indio_dev;
>>> struct iio_buffer *buffer;
>>> + int i;
>>>
>>> indio_dev = devm_iio_device_alloc(&device->dev, sizeof(*als));
>>> if (!indio_dev)
>>> @@ -191,6 +205,9 @@ static int acpi_als_add(struct acpi_device *device)
>>> als->device = device;
>>> mutex_init(&als->lock);
>>>
>>> + for (i = 0; i < ARRAY_SIZE(acpi_als_quirks); i++)
>>> + acpi_als_quirks[i](als);
>>> +
>>> indio_dev->name = ACPI_ALS_DEVICE_NAME;
>>> indio_dev->dev.parent = &device->dev;
>>> indio_dev->info = &acpi_als_info;
>>
>> --
>> Best regards,
>> Marek Vasut


-- 
Best regards,
Marek Vasut