linux-kernel - Re: [PATCH v6 09/26] drm/bridge: move devm_drm_of_get_bridge and drmm_of_get_bridge to drm

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Message-ID: <20250207095421.07ca853f@booty>
Date: Fri, 7 Feb 2025 09:54:21 +0100
From: Luca Ceresoli <luca.ceresoli@...tlin.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Simona Vetter <simona@...ll.ch>, Inki Dae <inki.dae@...sung.com>, Jagan
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Subject: Re: [PATCH v6 09/26] drm/bridge: move devm_drm_of_get_bridge and
 drmm_of_get_bridge to drm_bridge.c

On Fri, 7 Feb 2025 04:52:20 +0200
Dmitry Baryshkov <dmitry.baryshkov@...aro.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@...tlin.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"?
 * 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)
 - devm_ and drmm_ variants of the above

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