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SubjectRe: [PATCH] dell-laptop: Fix backlight detection
On Sunday 08 July 2018 17:02:20 Damien Thébault wrote:
> Fix return code check for "max brightness" ACPI call.
>
> The dell laptop ACPI video brightness control is not present on dell
> laptops anymore, but was present in older kernel versions.
>
> The code that checks the return value is incorrect since the SMM
> refactoring.
>
> The old code was:
> if (buffer->output[0] == 0)
>
> Which was changed to:
> ret = dell_send_request(...)
> if (ret)
>
> However, dell_send_request() will return 0 if buffer->output[0] == 0,
> so we must change the check to:
> if (ret == 0)

You are right, dell_send_request() return non-zero value on error.

> This issue was found on a Dell M4800 laptop, and the fix tested on it
> as well.
>
> Fixes: 549b4930f057 ("dell-smbios: Introduce dispatcher for SMM calls")
> Signed-off-by: Damien Thébault <damien@dtbo.net>
> Tested-by: Damien Thébault <damien@dtbo.net>
> ---
> drivers/platform/x86/dell-laptop.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/platform/x86/dell-laptop.c
> b/drivers/platform/x86/dell-laptop.c index f1fa8612db40..06978c14c83b
> 100644 --- a/drivers/platform/x86/dell-laptop.c
> +++ b/drivers/platform/x86/dell-laptop.c
> @@ -2185,7 +2185,7 @@ static int __init dell_init(void)
> dell_fill_request(&buffer, token->location, 0, 0, 0);
> ret = dell_send_request(&buffer,
> CLASS_TOKEN_READ,
> SELECT_TOKEN_AC);
> - if (ret)
> + if (ret == 0)
> max_intensity = buffer.output[3];
> }
>

Reviewed-by: Pali Rohár <pali.rohar@gmail.com>

--
Pali Rohár
pali.rohar@gmail.com
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