linux-kernel - Re: [PATCH v7 4/7] media: platform: amd: isp4 subdev and firmware loading handling added

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Message-ID: <7af839c1-9998-4bc3-b6b3-27dde923fb77@amd.com>
Date: Thu, 15 Jan 2026 15:51:09 +0800
From: "Du, Bin" <bin.du@....com>
To: Sakari Ailus <sakari.ailus@...ux.intel.com>
Cc: mchehab@...nel.org, hverkuil@...all.nl,
 laurent.pinchart+renesas@...asonboard.com, bryan.odonoghue@...aro.org,
 prabhakar.mahadev-lad.rj@...renesas.com, linux-media@...r.kernel.org,
 linux-kernel@...r.kernel.org, sultan@...neltoast.com,
 pratap.nirujogi@....com, benjamin.chan@....com, king.li@....com,
 gjorgji.rosikopulos@....com, Phil.Jawich@....com, Dominic.Antony@....com,
 mario.limonciello@....com, richard.gong@....com, anson.tsao@....com,
 Alexey Zagorodnikov <xglooom@...il.com>
Subject: Re: [PATCH v7 4/7] media: platform: amd: isp4 subdev and firmware
 loading handling added



On 1/15/2026 5:07 AM, Sakari Ailus wrote:
> Hi Bin,
> 
> On Wed, Jan 14, 2026 at 06:34:34PM +0800, Du, Bin wrote:
>>> The increment could probably be expressed as seen &= ~BIT(i).
>>>
>>
>> Quoted below is Sultan's reply regarding this, Would it be acceptable to
>> leave it unchanged?
>>
>> "Yes it can be, but it adds several more instructions before the loop body,
>> without any improvement to the loop body (the sarx in the loop body is
>> replaced
>> by andn). The right shift trick is faster and this is a hot path (IRQ
>> handler).
> 
> Please see my reply to Sultan.
> 

Yes, I appreciate the instructive ideas from you and Sultan.

>>>> +static int isp4sd_sdev_link_validate(struct media_link *link)
>>>> +{
>>>> +	return 0;
>>>
>>> Uh-oh.
>>>
>>> What is actually being configured via the sub-device? There is no device
>>> node either, is there? Are there plans for future developments, apart from
>>> possibly making the ISP and the sensor controllable by the host?
>>>
>>
>> Yes, you are correct. For the first version, no device node and
>> configuration for the sub-device now. Possible future development plan is
>> under internal discussion.
> 
> You can drop these for now.
> 

Sure, will remove these now and reintroduce them when they're needed in 
the future.

-- 
Regards,
Bin