Re: [PATCH v2 2/4] drm: mxsfb: Add optional DPI output bus-width configuration

[Frank Li]

On Thu, Jul 23, 2026 at 05:53:32PM +0200, Francesco Dolcini wrote:
> On Thu, Jul 23, 2026 at 10:47:36AM -0500, Frank Li wrote:
> > On Thu, Jul 23, 2026 at 11:38:09AM +0200, Francesco Dolcini wrote:
> > > From: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
> > >
> > > LCDIF programs LCD_DATABUS_WIDTH from the selected media bus format. The
> > > format reported by the downstream panel or bridge describes the display
> > > input, but it does not describe how the LCDIF data pins are physically
> > > wired on the board.
> > >
> > > These can differ. For example, a 16-bit LCDIF bus can be connected to a
> > > 24-bit display by wiring the available color bits to the corresponding
> > > display inputs. In that case, using the display's 24-bit format to
> > > configure LCDIF selects the wrong data-bus mode and changes the assignment
> > > of color bits on the LCD_DATA pins.
> > >
> > > Read the optional bus-width endpoint property from the LCDIF output port
> > > and use it to select the media bus format used to configure LCDIF. This
> > > allows the LCDIF bus mode to describe the physical interface
> > > independently of the downstream display format.
> > >
> > > When the optional property is absent, continue using the format reported
> > > by the downstream display device, preserving the existing behavior.
> > >
> > > Signed-off-by: Francesco Dolcini <francesco.dolcini@xxxxxxxxxxx>
> > > ---
> > > v2: use the common bus-width property instead of the legacy interface-pix-fmt
> > > ---
> > >  drivers/gpu/drm/mxsfb/mxsfb_drv.c | 24 ++++++++++++++++++++++++
> > >  drivers/gpu/drm/mxsfb/mxsfb_drv.h |  2 ++
> > >  drivers/gpu/drm/mxsfb/mxsfb_kms.c | 12 ++++++++++++
> > >  3 files changed, 38 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/mxsfb/mxsfb_drv.c b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > > index 9b8fbda85d28..0545718a4b65 100644
> > > --- a/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > > +++ b/drivers/gpu/drm/mxsfb/mxsfb_drv.c
> > > @@ -12,7 +12,10 @@
> > >  #include <linux/clk.h>
> > >  #include <linux/dma-mapping.h>
> > >  #include <linux/io.h>
> > > +#include <linux/media-bus-format.h>
> > >  #include <linux/module.h>
> > > +#include <linux/of.h>
> > > +#include <linux/of_graph.h>
> > >  #include <linux/platform_device.h>
> > >  #include <linux/property.h>
> > >  #include <linux/pm_runtime.h>
> > > @@ -209,7 +212,10 @@ static int mxsfb_load(struct drm_device *drm,
> > >  		      const struct mxsfb_devdata *devdata)
> > >  {
> > >  	struct platform_device *pdev = to_platform_device(drm->dev);
> > > +	struct device_node *np = pdev->dev.of_node;
> > >  	struct mxsfb_drm_private *mxsfb;
> > > +	struct device_node *ep;
> > > +	u32 bus_width = 0;
> > >  	int ret;
> > >
> > >  	mxsfb = devm_kzalloc(&pdev->dev, sizeof(*mxsfb), GFP_KERNEL);
> > > @@ -236,6 +242,24 @@ static int mxsfb_load(struct drm_device *drm,
> > >  	if (IS_ERR(mxsfb->clk_disp_axi))
> > >  		mxsfb->clk_disp_axi = NULL;
> > >
> > > +	ep = of_graph_get_next_endpoint(np, NULL);
> >
> > use auto cleanup
> >
> > 	struct device_node *ep __free(device_node) = of_graph_get_next_endpoint(np, NULL);
>
> Does it makes the code more read-able or better in this specific case? I
> would say no, to me it is more compact and clear the way it is.

Recently there are bunch of patch to fix miss of_put_node(). auto cleanup
help avoid manual to manage it and let us to force key part.

recently, perfer use fwnode_graph_get_next_endpoint() and other fwnode_xxx
node function.

it is also okay to keep use of_xxx() to align existing code.

Frank

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