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

From: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
To: Johan Hovold <johan@kernel.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>,
	<linux-serial@vger.kernel.org>, <linux-acpi@vger.kernel.org>,
	<linux-kernel@vger.kernel.org>,
	<nobuhiro1.iwamatsu@toshiba.co.jp>,
	<shrirang.bagul@canonical.com>, <stable@vger.kernel.org>,
	Rob Herring <robh@kernel.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Hans de Goede <hdegoede@redhat.com>
Subject: Re: [PATCH] serdev: Don't claim unsupported serial devices
Date: Wed, 18 Dec 2019 18:09:46 +0900	[thread overview]
Message-ID: <87o8w6ngo5.fsf@kokedama.swc.toshiba.co.jp> (raw)
In-Reply-To: <20191218085648.GI22665@localhost> (Johan Hovold's message of "Wed, 18 Dec 2019 09:56:48 +0100")

Hi Johan,

Johan Hovold <johan@kernel.org> writes:

> 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@vger.kernel.org
>> Signed-off-by: Punit Agrawal <punit1.agrawal@toshiba.co.jp>
>> Cc: Rob Herring <robh@kernel.org>
>> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> Cc: Johan Hovold <johan@kernel.org>
>> Cc: Hans de Goede <hdegoede@redhat.com>
>> ---
>> 
>> 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?
>
>> [0] https://www.spinics.net/lists/linux-serial/msg36646.html
>> 
>>  drivers/tty/serdev/core.c | 10 ++++++++++
>>  1 file changed, 10 insertions(+)
>> 
>> diff --git a/drivers/tty/serdev/core.c b/drivers/tty/serdev/core.c
>> index 226adeec2aed..0d64fb7d4f36 100644
>> --- a/drivers/tty/serdev/core.c
>> +++ b/drivers/tty/serdev/core.c
>> @@ -663,6 +663,12 @@ static acpi_status acpi_serdev_register_device(struct serdev_controller *ctrl,
>>  	return AE_OK;
>>  }
>>  
>> +static const struct acpi_device_id serdev_blacklist_devices[] = {
>> +	{"INT3511", 0},
>> +	{"INT3512", 0},
>
> Nit: Would you mind adding a space after { and before }?

Sure - no problem. I'll include it in the next posting.

Thanks for having a look.

>
>> +	{ },
>> +};
>
> Johan