linux-kernel - Re: [PATCH v2 2/6] drm/meson/dw-hdmi: convert to of_drm_find_and_get

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Message-ID: <CAFBinCCz+MobtXYdiyWRBBFBDo77iULLOZ1p2i4fAVnpJ1NzJw@mail.gmail.com>
Date: Mon, 19 Jan 2026 22:24:15 +0100
From: Martin Blumenstingl <martin.blumenstingl@...glemail.com>
To: Luca Ceresoli <luca.ceresoli@...tlin.com>
Cc: Neil Armstrong <neil.armstrong@...aro.org>, Kevin Hilman <khilman@...libre.com>, 
	Jerome Brunet <jbrunet@...libre.com>, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, linux-amlogic@...ts.infradead.org, 
	linux-arm-kernel@...ts.infradead.org, imx@...ts.linux.dev, 
	linux-mediatek@...ts.infradead.org, linux-samsung-soc@...r.kernel.org, 
	linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH v2 2/6] drm/meson/dw-hdmi: convert to of_drm_find_and_get_bridge()

Hi Luca,

On Tue, Jan 13, 2026 at 6:31 PM Luca Ceresoli <luca.ceresoli@...tlin.com> wrote:
[...]
> >> @@ -789,8 +789,12 @@ static void meson_dw_hdmi_unbind(struct device *dev, struct device *master,
> >>                                    void *data)
> >>  {
> >>         struct meson_dw_hdmi *meson_dw_hdmi = dev_get_drvdata(dev);
> >> +       struct platform_device *pdev = to_platform_device(dev);
> >> +       int irq = platform_get_irq(pdev, 0);
> >>
> >> +       devm_free_irq(dev, irq, meson_dw_hdmi);
> > I have one question (so I can understand things better):
> > is there a particular reason why you went with free'ing the IRQ
> > instead of "just" masking it (so the hardware won't fire anymore of
> > those IRQs)?
>
> One reason is symmetry: _bind requests the irq, so _unbind does the
> reverse.
>
> Another is I don't have the hardware, so I wanted my changes to be as small
> and clear as possible.
Understood, thanks!

> In principle one could request/free the irq in probe/remove and then
> enable/disable it in bind/unbind. Whether it would be a good or bad idea I
> don't know, but surely it would be more complex and I wouldn't want to do
> it without any chance to test it on hardware.
>
> Also, that would only optimize the case of multiple bind/unbind cycles,
> which are not quite realistic without bridge hotplug. And brigde hotplug
> does not exist yet in mainline, and when it will arrive it will be used
> only for a few use cases.
>
> I hope this answers your question.
Yes, I was curious whether you considered devm_free_irq() as the only
"correct" approach (in this case I would have recommended a comment)
or whether other approaches are fine too.
This is useful knowledge for me in case we ever need to restructure the driver.


Best regards,
Martin