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

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Date:   Wed, 18 Dec 2019 11:05:40 +0100
From:   Hans de Goede <hdegoede@...hat.com>
To:     Punit Agrawal <punit1.agrawal@...hiba.co.jp>,
        linux-serial@...r.kernel.org
Cc:     linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        nobuhiro1.iwamatsu@...hiba.co.jp, shrirang.bagul@...onical.com,
        stable@...r.kernel.org, Rob Herring <robh@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johan Hovold <johan@...nel.org>
Subject: Re: [PATCH] serdev: Don't claim unsupported serial devices

Hi,

On 18-12-2019 07:56, 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@...r.kernel.org
> Signed-off-by: Punit Agrawal <punit1.agrawal@...hiba.co.jp>
> Cc: Rob Herring <robh@...nel.org>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Johan Hovold <johan@...nel.org>
> Cc: Hans de Goede <hdegoede@...hat.com>

Thank you for addressing this long standing issue.

The basic approach here looks good to me, once the minor
comments from other reviewers are addressed you can add my:

Acked-by: Hans de Goede <hdegoede@...hat.com>

to the next version.

Regards,

Hans



> ---
> 
> Hi,
> 
> The patch has been updated based on feedback recieved on the RFC[0].
> 
> Please consider merging if there are no objections.
> 
> Thanks,
> Punit
> 
> [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},
> +	{ },
> +};
> +
>   static acpi_status acpi_serdev_add_device(acpi_handle handle, u32 level,
>   					  void *data, void **return_value)
>   {
> @@ -675,6 +681,10 @@ static acpi_status acpi_serdev_add_device(acpi_handle handle, u32 level,
>   	if (acpi_device_enumerated(adev))
>   		return AE_OK;
>   
> +	/* Skip if black listed */
> +	if (!acpi_match_device_ids(adev, serdev_blacklist_devices))
> +		return AE_OK;
> +
>   	if (acpi_serdev_check_resources(ctrl, adev))
>   		return AE_OK;
>   
>