Hi,
On Sun, Feb 6, 2022 at 7:44 AM Sam Ravnborg <sam@xxxxxxxxxxxx> wrote:
>
> There is a number of bridge drivers that supports a single media bus
> format for DSI. Add a helper to avoid duplicating the code.
>
> Signed-off-by: Sam Ravnborg <sam@xxxxxxxxxxxx>
> ---
> drivers/gpu/drm/drm_atomic_helper.c | 41 +++++++++++++++++++++++++++++
> include/drm/drm_atomic_helper.h | 7 +++++
> 2 files changed, 48 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
> index a7a05e1e26bb..94f313dc196f 100644
> --- a/drivers/gpu/drm/drm_atomic_helper.c
> +++ b/drivers/gpu/drm/drm_atomic_helper.c
> @@ -3549,3 +3549,44 @@ drm_atomic_helper_bridge_propagate_bus_fmt(struct drm_bridge *bridge,
> return input_fmts;
> }
> EXPORT_SYMBOL(drm_atomic_helper_bridge_propagate_bus_fmt);
> +
> +/**
> + * drm_atomic_helper_bridge_dsi_input_bus_fmt - Define one DSI output format
Is the description right? It's called "input" format but it defines an
output format?
> + * @bridge: bridge control structure
> + * @bridge_state: new bridge state
> + * @crtc_state: new CRTC state
> + * @conn_state: new connector state
> + * @output_fmt: tested output bus format
> + * @num_input_fmts: will contain the size of the returned array
Maybe indicate that it's always 1 in the comments?
> + *
> + * This helper is an implementation of the
> + * &drm_bridge_funcs.atomic_get_input_bus_fmts operation for bridges that supports
> + * a single DSI media bus format MEDIA_BUS_FMT_RGB888_1X24.
> + *
> + * RETURNS
kernel-doc can't parse this return syntax and warns:
warning: No description found for return value of
'drm_atomic_helper_bridge_dsi_input_bus_fmt'
> + * A format array with one entry containing MEDIA_BUS_FMT_RGB888_1X24,
> + * or NULL if the allocation failed
> + */
> +u32 *
> +drm_atomic_helper_bridge_dsi_input_bus_fmt(struct drm_bridge *bridge,
> + struct drm_bridge_state *bridge_state,
> + struct drm_crtc_state *crtc_state,
> + struct drm_connector_state *conn_state,
> + u32 output_fmt,
> + unsigned int *num_input_fmts)
> +{
> + u32 *input_fmts;
> +
> + *num_input_fmts = 0;
> +
> + input_fmts = kcalloc(MAX_INPUT_SEL_FORMATS, sizeof(*input_fmts), GFP_KERNEL);
I probably wouldn't have bothered with `kcalloc` for something that's
always just one value and you're setting it. Why not just
input_fmts = kmalloc(sizeof(*input_fmts), GFP_KERNEL);
...also MAX_INPUT_SEL_FORMATS isn't defined. I guess that's why you
said it didn't compile?
Also: if it was common for others to want to provide fixed formats, I
wonder about adding a helper function that did most of the work here?
Dunno what it would be named since it's already a bit a of handful,
but I'd expect to call it like:
static const u32 formats[] = { MEDIA_BUS_FMT_RGB888_1X24 };
return my_neat_helper(formats, ARRAY_SIZE(formats), num_output_formats)
Then my_neat_helper() could do kmemdup() on the array passed and fill
in "num_output_formats" to be either the array size of 0 (if the
kmemdup failed).
> + if (!input_fmts)
> + return NULL;
> +
> + /* This is the DSI-end bus format */
> + input_fmts[0] = MEDIA_BUS_FMT_RGB888_1X24;
I'm not an expert, but I'm curious. Can't DSI run in other formats?
...or maybe I'm misunderstanding what this is for. I guess I'm not
sure how it relates to:
enum mipi_dsi_pixel_format {
MIPI_DSI_FMT_RGB888,
MIPI_DSI_FMT_RGB666,
MIPI_DSI_FMT_RGB666_PACKED,
MIPI_DSI_FMT_RGB565,
};
-Doug
