> -----Original Message----- > From: Pali Rohár [mailto:pali.rohar@xxxxxxxxx] > Sent: Sunday, July 8, 2018 8:09 AM > To: Damien Thébault > Cc: Matthew Garrett; Darren Hart; Andy Shevchenko; Limonciello, Mario; platform- > driver-x86@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx > Subject: Re: [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@xxxxxxxx> > > Tested-by: Damien Thébault <damien@xxxxxxxx> > > --- > > 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@xxxxxxxxx> > Thanks for this catch. Reviewed-by: Mario Limonciello <mario.limonciello@xxxxxxxx> This should probably go to stable as well.
