Re: [PATCH v6 09/26] drm/bridge: move devm_drm_of_get_bridge and drmm_of_get_bridge to drm_bridge.c

Dmitry Baryshkov
2025-02-07T20:30:00Z

On Fri, Feb 07, 2025 at 09:54:21AM +0100, Luca Ceresoli wrote:
> On Fri, 7 Feb 2025 04:52:20 +0200
> Dmitry Baryshkov <dmitry.baryshkov@linaro.org> wrote:
>
> > On Thu, Feb 06, 2025 at 07:14:24PM +0100, Luca Ceresoli wrote:
> > > devm_drm_of_get_bridge() and drmm_of_get_bridge() do not have anything to
> > > do with struct drm_panel anymore, they just manage bridges. So move them
> > > from bridge/panel.c to drm_bridge.c.
> > >
> > > Move also of_drm_find_bridge_by_endpoint() which is used only by
> > > devm_drm_of_get_bridge() and drmm_of_get_bridge().
> > >
> > > No code changes, only move functions to a different file within the same
> > > module and add an #include as needed.
> > >
> > > Signed-off-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
> > >
> > > ---
> > >
> > > This patch was added in v6.
> > > ---
> > > drivers/gpu/drm/bridge/panel.c | 102 -----------------------------------------
> > > drivers/gpu/drm/drm_bridge.c | 100 ++++++++++++++++++++++++++++++++++++++++
> > > 2 files changed, 100 insertions(+), 102 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/bridge/panel.c b/drivers/gpu/drm/bridge/panel.c
> > > index 6995de605e7317dd1eb153afd475746ced764712..1230ae50b2020e7a9306cac83009dd600dd61d26 100644
> > > --- a/drivers/gpu/drm/bridge/panel.c
> > > +++ b/drivers/gpu/drm/bridge/panel.c
> > > @@ -418,49 +418,6 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
> > > }
> > > EXPORT_SYMBOL_GPL(drm_of_find_panel_or_bridge);
> > >
> > > -/**
> > > - * of_drm_find_bridge_by_endpoint - return drm_bridge connected to an endpoint
> > > - * @np: device tree node containing encoder output ports
> > > - * @port: port in the device tree node
> > > - * @endpoint: endpoint in the device tree node
> > > - * @bridge: pointer to hold returned drm_bridge (must not be NULL)
> > > - *
> > > - * Given a DT node's port and endpoint number, find the connected node and
> > > - * return the associated struct drm_bridge.
> > > - *
> > > - * Returns zero if successful, or one of the standard error codes if it fails.
> > > - */
> > > -static int of_drm_find_bridge_by_endpoint(const struct device_node *np,
> > > - int port, int endpoint,
> > > - struct drm_bridge **bridge)
> >
> > I'd say make this function the main API instead (and name it drm_of
> > rather than of_drm, this can happen in the previous patch).
>
> I agree there should be a small number of APIs for the foreseeable
> future (and any number of, hopefully decreasing-at-some-point,
> deprecated ones).
>
> And I agree this one ^ and the devm_drm_of_get_bridge() below are
> equivalent, despite having different signatures, and so one should
> disappear.
>
> So, time to think about what APIs we want. Some thoughts of mine:
>
> * I prefer "get" over "find", looks more intuitive as these functions
> will drm_bridge_get()
> * Is there a logic between of_drm_ and drm_of_? Just "the former is
> old and deprecated"?

I don't know, it might be historical. Nevertheless, I think, having just
drm_ prefix for all DRM-related symbols is a good idea.

> * Since getting bridges via the endpoint is the preferred way, I'd
> like this function to have a shorter name than its variants
> * Returning a struct drm_bridge err_ptr looks better to me than
> returning an error and the bridge via a ptr-to-ptr, especially as we
> don't have anymore the case of returning a panel or a bridge from
> the same function
>
> So, bottom line, we'd have:
>
> - struct drm_bridge *drm_of_get_bridge(np, port, endpoint)
> - struct drm_bridge *drm_of_get_bridge_by_node(bridge_np)

I think these two are fine, please go with them

> - devm_ and drmm_ variants of the above

These two are only necessary for the refcounted bridges. I'd say, skip
them as a part of the panel / bridge patchset. Please don't
overcomplicate it too much.

>
> or a subset of these, in case some is not needed.
>
> What are your opinions?
>
> > > -struct drm_bridge *devm_drm_of_get_bridge(struct device *dev,
> > > - struct device_node *np,
> > > - u32 port, u32 endpoint)
>
> ^ kept for reference
>
> Luca
>
> --
> Luca Ceresoli, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com

--
With best wishes
Dmitry