Re: [PATCH v4 2/2] phy: qcom-mipi-csi2: Add a CSI2 MIPI DPHY driver

[Neil Armstrong]

On 3/19/26 16:18, Bryan O'Donoghue wrote:
> On 19/03/2026 14:56, Vladimir Zapolskiy wrote:
> > > There's no reason to remove that from CAMSS - it would be an ABI break
> > > in user-space anyway.
> >
> > If technically CAMSS CSIPHY could be excluded from the list of CAMSS media
> > subdevices, then for the sake of simplification it should be done for all
> > supported platforms in advance, such a change will be independent from this
> > particular phy series, and vice versa, this CAMSS only driver change will
> > prepare a ground for media-less CAMSS CSIPHY device drivers, hence it shall
> > precede this particular CAMSS CSIPHY series.
> >
> > For backward compatibility with userspace a noop stub will be good enough,
> > it's not an issue at all.
>
> The standalone PHY driver doesn't require removing the CSIPHY media
> entity from CAMSS. They serve different purposes and coexist - its important to have a NOP from user-space perspective for legacy and indeed for new implementations.
>
> How the PHY gets represented in the kernel is of zero interest to user-sapce.
>
> That said, stubbing out the media entity is independent work that can happen in any order and IMO is a separate debate. Whether or not CSIPHY init sequences live inside of a monolithic CAMSS driver or live inside off a discrete csiphy driver is not related to the media graph.
>
> Happy to have that debate - and if indicated, carefully apply patches separately.

So what does this actually solves ?

Neil

> ---
> bod