platform/x86: dell-laptop: Fix backlight detection
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) This issue was found on a Dell M4800 laptop, and the fix tested on it as well. Fixes: 549b4930 ("dell-smbios: Introduce dispatcher for SMM calls") Signed-off-by: NDamien Thébault <damien@dtbo.net> Tested-by: NDamien Thébault <damien@dtbo.net> Reviewed-by: NPali Rohár <pali.rohar@gmail.com> Reviewed-by: NMario Limonciello <mario.limonciello@dell.com> Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>
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