Re: [PATCH V2] rtc: mc146818: Dont test for bit 0-5 in Register D

[Thomas Gleixner]

On Mon, Feb 01 2021 at 11:32, Linus Torvalds wrote:
> On Mon, Feb 1, 2021 at 11:24 AM Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
>>
>> While it cures the problem on the reporters machine it breaks machines
>> with Intel chipsets which use bit 0-5 of the D register. So check only
>> for bit 6 being 0 which is the case on these Intel machines as well.
>
> This looks fine, but it might also be worth it simply just checking
> for the only really special value: 0xff, and going "ok, that looks
> like missing hardware".
>
> That's what a few other drivers historically do in their probing
> routines, so it's not unheard of (ie you can find drivers doing that
> kind of
>
>         /* If we read 0xff from the LSR, there is no UART here. */
>         if (inb(.. port ..) == 0xff)
>
> in their init routines.
>
> Not a big deal either way, I just think it would be more in like with
> what other places do in similar situations

Yeah, we can do that as well. Either way is fine.

Thanks,

        tglx