linux-kernel - Re: [PATCH 1/3] serdev: ttyport: add devt for tty port

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Message-ID: <20200518145651.GL25962@localhost>
Date:   Mon, 18 May 2020 16:56:51 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Claire Chang <tientzu@...omium.org>
Cc:     robh@...nel.org, gregkh@...uxfoundation.org, jslaby@...e.com,
        long.cheng@...iatek.com, changqi.hu@...iatek.com,
        linux-serial@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] serdev: ttyport: add devt for tty port

On Wed, May 06, 2020 at 03:23:12PM +0800, Claire Chang wrote:
> serial_match_port() uses devt to match devices. However, when serdev
> registers a tty port, devt has never been set. This makes
> device_find_child() always return NULL.
> 
> Assign devt in serdev_tty_port_register() to fix this.
> 
> Signed-off-by: Claire Chang <tientzu@...omium.org>
> ---
>  drivers/tty/serdev/serdev-ttyport.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/tty/serdev/serdev-ttyport.c b/drivers/tty/serdev/serdev-ttyport.c
> index d367803e2044f..9238119173a47 100644
> --- a/drivers/tty/serdev/serdev-ttyport.c
> +++ b/drivers/tty/serdev/serdev-ttyport.c
> @@ -267,6 +267,7 @@ struct device *serdev_tty_port_register(struct tty_port *port,
>  {
>  	struct serdev_controller *ctrl;
>  	struct serport *serport;
> +	dev_t devt = MKDEV(drv->major, drv->minor_start) + idx;
>  	int ret;
>  
>  	if (!port || !drv || !parent)
> @@ -282,6 +283,7 @@ struct device *serdev_tty_port_register(struct tty_port *port,
>  	serport->tty_drv = drv;
>  
>  	ctrl->ops = &ctrl_ops;
> +	ctrl->dev.devt = devt;

This is conceptually wrong. A serdev controller is not a tty class
device with a corresponding character device.

It seems you need to rethink how serial core should handle the wakeup
flags with respect to serdev.

>  
>  	port->client_ops = &client_ops;
>  	port->client_data = ctrl;

Johan