linux-kernel - Re: [PATCH v2 1/1] drm/bridge: lontium-lt9611uxc: use irq as optional parameter

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Message-Id: <DFI8X9FKRV12.1XNFGJDUWR5PR@bootlin.com>
Date: Wed, 07 Jan 2026 10:23:01 +0100
From: "Luca Ceresoli" <luca.ceresoli@...tlin.com>
To: "Vladimir Yakovlev" <vovchkir@...il.com>
Cc: <Laurent.pinchart@...asonboard.com>, <airlied@...il.com>,
 <andrzej.hajda@...el.com>, <dmitry.baryshkov@....qualcomm.com>,
 <dri-devel@...ts.freedesktop.org>, <jernej.skrabec@...il.com>,
 <jonas@...boo.se>, <linux-kernel@...r.kernel.org>,
 <maarten.lankhorst@...ux.intel.com>, <mripard@...nel.org>,
 <neil.armstrong@...aro.org>, <rfoss@...nel.org>, <simona@...ll.ch>,
 <tzimmermann@...e.de>
Subject: Re: [PATCH v2 1/1] drm/bridge: lontium-lt9611uxc: use irq as
 optional parameter

On Wed Jan 7, 2026 at 4:23 AM CET, Vladimir Yakovlev wrote:
> On some systems the interrupt pin may not be used.
> In this case we exclude DRM_BRIDGE_OP_HPD from supported operations,
> after which a polling thread is started to detect the connection.
> (the default polling period for DRM is 10 seconds)
>
> Signed-off-by: Vladimir Yakovlev <vovchkir@...il.com>
> ---
>  drivers/gpu/drm/bridge/lontium-lt9611uxc.c | 20 +++++++++++++-------
>  1 file changed, 13 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
> index bb5cff021c93..f7a74ec1f170 100644
> --- a/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
> +++ b/drivers/gpu/drm/bridge/lontium-lt9611uxc.c
> @@ -851,19 +851,25 @@ static int lt9611uxc_probe(struct i2c_client *client)
>  	init_waitqueue_head(&lt9611uxc->wq);
>  	INIT_WORK(&lt9611uxc->work, lt9611uxc_hpd_work);
>
> -	ret = devm_request_threaded_irq(dev, client->irq, NULL,
> -					lt9611uxc_irq_thread_handler,
> -					IRQF_ONESHOT, "lt9611uxc", lt9611uxc);
> -	if (ret) {
> -		dev_err(dev, "failed to request irq\n");
> -		goto err_disable_regulators;
> +	if (client->irq) {
> +		ret = devm_request_threaded_irq(dev, client->irq, NULL,
> +						lt9611uxc_irq_thread_handler,
> +						IRQF_ONESHOT, "lt9611uxc", lt9611uxc);
> +		if (ret) {
> +			dev_err(dev, "failed to request irq\n");
> +			goto err_disable_regulators;
> +		}
> +		dev_dbg(dev, "Uses IRQ\n");
> +	} else {
> +		dev_dbg(dev, "The interrupt (IRQ) is not specified in the DTS.\n");
> +		dev_dbg(dev, "Check the interrupt (IRQ) or polling will be used!!!\n");
>  	}

Thanks for having moved form a warning to a dbg. However these 2 lines are
overly verbose and that's not really needed. I would prefer to see all
those 3 dev_dbg() disappear honestly, being polling a perfectly supported
use case here. But if you really really want to keep them, at least replace
these 2 lines with just a "Uses polling\n" which gives the same info. Also
the 2 consecutive dev_dbg() may mix with other logging, making it awkward
to read in the logs.

Luca

--
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com