linux-kernel - Re: [PATCH v5 4/7] drm/bridge: dw-hdmi: Add API dw_hdmi_set_sample

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Message-ID: <CAA+D8AP8eJ8_pueq1ZSb-ORzTJbNT7HOwKFOO5ZCXqgqoQ1qGQ@mail.gmail.com>
Date: Fri, 19 Sep 2025 11:43:05 +0800
From: Shengjiu Wang <shengjiu.wang@...il.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Luca Ceresoli <luca.ceresoli@...tlin.com>, Shengjiu Wang <shengjiu.wang@....com>, 
	andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org, 
	Laurent.pinchart@...asonboard.com, jonas@...boo.se, jernej.skrabec@...il.com, 
	maarten.lankhorst@...ux.intel.com, tzimmermann@...e.de, airlied@...il.com, 
	simona@...ll.ch, lumag@...nel.org, dianders@...omium.org, 
	cristian.ciocaltea@...labora.com, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org, victor.liu@....com, shawnguo@...nel.org, 
	s.hauer@...gutronix.de, kernel@...gutronix.de, festevam@...il.com, 
	imx@...ts.linux.dev, linux-arm-kernel@...ts.infradead.org, robh@...nel.org, 
	krzk+dt@...nel.org, conor+dt@...nel.org, p.zabel@...gutronix.de, 
	devicetree@...r.kernel.org, l.stach@...gutronix.de, perex@...ex.cz, 
	tiwai@...e.com, linux-sound@...r.kernel.org
Subject: Re: [PATCH v5 4/7] drm/bridge: dw-hdmi: Add API dw_hdmi_set_sample_iec958()
 for iec958 format

Hi Luca

On Wed, Sep 10, 2025 at 6:29 PM Shengjiu Wang <shengjiu.wang@...il.com> wrote:
>
> Hi
>
> On Tue, Sep 9, 2025 at 2:39 PM Maxime Ripard <mripard@...nel.org> wrote:
> >
> > Hi,
> >
> > On Wed, Sep 03, 2025 at 06:41:05PM +0800, Shengjiu Wang wrote:
> > > On Tue, Sep 2, 2025 at 12:52 AM Luca Ceresoli <luca.ceresoli@...tlin.com> wrote:
> > > >
> > > > Hello Shengjiu,
> > > >
> > > > On Thu, 21 Aug 2025 15:31:28 +0800
> > > > Shengjiu Wang <shengjiu.wang@....com> wrote:
> > > >
> > > > > Add API dw_hdmi_set_sample_iec958() for IEC958 format because audio device
> > > > > driver needs IEC958 information to configure this specific setting.
> > > > >
> > > > > Signed-off-by: Shengjiu Wang <shengjiu.wang@....com>
> > > > > Acked-by: Liu Ying <victor.liu@....com>
> > > >
> > > > [...]
> > > >
> > > > > +void dw_hdmi_set_sample_iec958(struct dw_hdmi *hdmi, unsigned int iec958)
> > > > > +{
> > > > > +     mutex_lock(&hdmi->audio_mutex);
> > > > > +     hdmi->sample_iec958 = iec958;
> > > > > +     mutex_unlock(&hdmi->audio_mutex);
> > > > > +}
> > > >
> > > > Apologies for jumping in the discussion as late as in v5, but I noticed
> > > > this patch and I was wondering whether this mutex_lock/unlock() is
> > > > really needed, as you're copying an int.
> > >
> > > Thanks for your comments.
> > >
> > > Seems it is not necessary to add mutex here. I just follow the code as
> > > other similar functions.  I will send a new version to update it.
> >
> > Let's not be smart about it. Next thing you know, someone will add
> > another field in there that would absolutely require a mutex and now
> > you're not race free anymore.
> >
> > Unless there's a real concern, the mutex must stay.
> >
>
> Ok, thanks for comments.  Then Patch v6 need to be dropped.
>
> Is there any other comments for this Patch v5?
> If no, can this series be accepted?
>

Can we have a conclusion that keeps the mutex as Maxime's comments?

Best regards
Shengjiu Wang