Re: [PATCH] serdev: Don't claim unsupported serial devices

[Punit Agrawal]

Johan Hovold <johan@xxxxxxxxxx> writes:

> On Thu, Dec 19, 2019 at 09:39:57AM +0100, Rafael J. Wysocki wrote:
>> On Wed, Dec 18, 2019 at 9:56 AM Johan Hovold <johan@xxxxxxxxxx> wrote:
>> >
>> > On Wed, Dec 18, 2019 at 03:56:46PM +0900, Punit Agrawal wrote:
>> > > Serdev sub-system claims all serial devices that are not already
>> > > enumerated. As a result, no device node is created for serial port on
>> > > certain boards such as the Apollo Lake based UP2. This has the
>> > > unintended consequence of not being able to raise the login prompt via
>> > > serial connection.
>> > >
>> > > Introduce a blacklist to reject devices that should not be treated as
>> > > a serdev device. Add the Intel HS UART peripheral ids to the blacklist
>> > > to bring back serial port on SoCs carrying them.
>> > >
>> > > Cc: stable@xxxxxxxxxxxxxxx
>> > > Signed-off-by: Punit Agrawal <punit1.agrawal@xxxxxxxxxxxxx>
>> > > Cc: Rob Herring <robh@xxxxxxxxxx>
>> > > Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
>> > > Cc: Johan Hovold <johan@xxxxxxxxxx>
>> > > Cc: Hans de Goede <hdegoede@xxxxxxxxxx>
>> > > ---
>> > >
>> > > Hi,
>> > >
>> > > The patch has been updated based on feedback recieved on the RFC[0].
>> > >
>> > > Please consider merging if there are no objections.
>> >
>> > Rafael, I vaguely remember you arguing for a white list when we
>> > discussed this at some conference. Do you have any objections to the
>> > blacklist approach taken here?
>> 
>> As a rule, I prefer whitelisting, because it only enables the feature
>> for systems where it has been tested and confirmed to work.
>> 
>> However, if you are convinced that in this particular case the feature
>> should work on the vast majority of systems with a few possible
>> exceptions, blacklisting is fine too.
>> 
>> It all depends on what the majority is, at least in principle.
>
> Ok, thanks. I don't have a preference either way in this case simply
> because I don't know the distribution you refer to.
>
> But if Hans thinks blacklisting is the way to go then let's do that. We
> haven't had that many reports about this, but if that were to change
> down the line, I guess we can always switch to whitelisting.
>
> Punit, feel free to add my
>
> Acked-by: Johan Hovold <johan@xxxxxxxxxx>
>
> after addressing the review comments you've gotten so far.

Thanks Johan.

I will post a new version with the updates and acks.