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

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Message-ID: <97288c51-954a-48a9-92b9-e165ce480707@nxp.com>
Date: Mon, 22 Sep 2025 11:02:34 +0800
From: Liu Ying <victor.liu@....com>
To: Shengjiu Wang <shengjiu.wang@...il.com>,
 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,
 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

On 09/10/2025, Shengjiu Wang 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.

To properly track the changelog with patchwork, can you send v7 to add
the mutex?

> 
> Is there any other comments for this Patch v5?
> If no, can this series be accepted?
> 
> Best regards
> Shengjiu Wang


-- 
Regards,
Liu Ying