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

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Message-ID: <aWgFf998f12tYWYX@kekkonen.localdomain>
Date: Wed, 14 Jan 2026 23:07:11 +0200
From: Sakari Ailus <sakari.ailus@...ux.intel.com>
To: "Du, Bin" <bin.du@....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

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.

> > > +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.

-- 
Kind regards,

Sakari Ailus