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SubjectRe: [PATCH] toshiba_acpi: Fix regression caused by backlight extra check code
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Hi Darren,

Sorry for the way late reply, I had to go out of town in a hurry.

2014-11-03 23:21 GMT-07:00 Darren Hart <dvhart@infradead.org>:
> On Mon, Nov 03, 2014 at 08:58:34PM -0700, Azael Avalos wrote:
>> Bug 86521 uncovered that some TOS6208 devices also return
>> non zero values on a write call to the backlight method,
>> thus getting caught and bailed out by the extra check code.
>>
>> This patch makes sure that the extra check is being done
>> on a TOS1900 device and then make the check for the broken
>> backlight code.
>>
>> Signed-off-by: Azael Avalos <coproscefalo@gmail.com>
>> ---
>> drivers/platform/x86/toshiba_acpi.c | 8 ++++++--
>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/platform/x86/toshiba_acpi.c b/drivers/platform/x86/toshiba_acpi.c
>> index ef3a190..e3fed12 100644
>> --- a/drivers/platform/x86/toshiba_acpi.c
>> +++ b/drivers/platform/x86/toshiba_acpi.c
>> @@ -944,9 +944,13 @@ static int set_lcd_brightness(struct toshiba_acpi_dev *dev, int value)
>> /* Extra check for "incomplete" backlight method, where the AML code
>> * doesn't check for HCI_SET or HCI_GET and returns TOS_SUCCESS,
>> * the actual brightness, and in some cases the max brightness.
>> + * Use the SPFC method as an indicator that we're on a TOS1900 device,
>> + * otherwise some TOS6208 devices might get bailed out, see bug 86521
>
> This needs a clearer description here in this comment, rather than redirecting
> the reader to a bug report (which may or may not exist when needed).

Alright, will do whenever we reach an agreement below.

>
>> */
>> - if (out[2] > 0 || out[3] == 0xE000)
>> - return -ENODEV;
>> + if (acpi_has_method(dev->acpi_dev->handle, "SPFC")) {
>
> Hrm, this checking for the existence of a specific method seems suspect to me.
> We would know if we are on a TOS1900 as we matches the acpi id already. Is the
> SPFC significant here, or is it just a "we only see SPFC on TOS1900 so it's a
> convenient test"? If the latter, it seems rather fragile and prone to other
> breakage to me.

Yeah, its the latter, the "SPFC" method is specific to TOS1900 devices.

All of the TOS1900 support the Toshiba specific backlight read-only,
and that test is just to get those implementations where the AML
code doesn't check for read/write registers, so far I've identified three
series of laptops with this issue (all Qosmios), X500, X505 and X75-A
(and there might be more around).

We could dissable backlight on all TOS1900 or add those three models
to the (growing) DMI list on video.c, but of course, I would like to keep
the code in-house, but that's just me :-)

>
> Rafael, any recommendations here?
>
>> + if (out[2] > 0 || out[3] == 0xE000)
>> + return -ENODEV;
>> + }
>>
>> return out[0] == TOS_SUCCESS ? 0 : -EIO;
>> }
>> --
>> 2.1.1
>>
>>
>
> --
> Darren Hart
> Intel Open Source Technology Center

Cheers
Azael



--
-- El mundo apesta y vosotros apestais tambien --


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