On Fri, Jul 21, 2023 at 8:17 AM Ying Liu <victor.liu@xxxxxxx> wrote: > On Thursday, July 20, 2023 7:28 PM Daniel Thompson <daniel.thompson@xxxxxxxxxx> wrote: > > On Thu, Jul 20, 2023 at 06:06:27AM +0000, Ying Liu wrote: > > > Bootloader may leave gpio direction as input and gpio value as logical low. > > > It hints that initial backlight power state should be > > FB_BLANK_POWERDOWN > > > since the gpio value is literally logical low. > > > > To be honest this probably "hints" that the bootloader simply didn't > > consider the backlight at all :-) . I'd rather the patch description > > focus on what circumstances lead to the current code making a bad > > decision. More like: > > > > If the GPIO pin is in the input state but the backlight is currently > > off due to default pull downs then ... > > How about this patch description? > > ---------------------------------8<------------------------------------------- > Without this patch, if gpio pin is in input state but backlight is currently s/Without this patch, if/If/ > off due to default pull downs, then initial power state is set to > FB_BLANK_UNBLANK in DT boot mode with phandle link and the backlight is > effectively turned on in gpio_backlight_probe(), which is undesirable > according to patch description of commit ec665b756e6f ("backlight: > gpio-backlight: Correct initial power state handling"). > > Quote: > --- > If in DT boot we have phandle link then leave the GPIO in a state which the > bootloader left it and let the user of the backlight to configure it further. > --- > > So, let's drop output gpio direction check and only check gpio value to set > the initial power state. > ---------------------------------8<------------------------------------------- -- With Best Regards, Andy Shevchenko