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

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Date:   Mon, 18 May 2020 18:04:39 +0800
From:   Claire Chang <tientzu@...omium.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     robh@...nel.org, jslaby@...e.com, long.cheng@...iatek.com,
        changqi.hu@...iatek.com, linux-serial@...r.kernel.org,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] serdev: ttyport: add devt for tty port

On Fri, May 15, 2020 at 8:46 PM Greg KH <gregkh@...uxfoundation.org> wrote:
>
> 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(+)
>
> So is existing code broken because of this?  Or does no one ever call
> device_find_child() on this?  Who needs/uses this?
>
> thanks,
>
> greg k-h

I'm not sure. Our use case is to control the wake on bluetooth
behavior by the power/wakeup node.

`readlink -f /sys/class/bluetooth/hci0`
/sys/devices/platform/soc/11003000.serial/serial0/serial0-0/bluetooth/hci0

and we'd like to use
`/sys/devices/platform/soc/11003000.serial/serial0/power/wakeup` to
decide whether to enable the in-band wakeup on uart host side.

Thanks,
Claire