til_settings: always describe relevant settings

The existing iterative *_setup() interface only described
settings not found, quietly accepting usable settings already
present in the til_settings_t.

This worked fine for the existing interactive text setup thing,
but it's especially problematic for providing a GUI setup
frontend.

This commit makes it so the *_setup() methods always describe
undescribed settings they recognize, leaving the setup frontend
loop calling into the *_setup() methods to both apply the
description validation if wanted and actually tie the description
to respective setting returned by the _setup() methods as being
related to the returned description.

A new helper called til_settings_get_and_describe_value() has
been introduced primarily for use of module setup methods to
simplify this nonsense, replacing the til_settings_get_value()
calls and surrounding logic, but retaining the til_setting_desc_t
definitions largely verbatim.

This also results in discarding of some ad-hoc
til_setting_desc_check() calls, now that there's a centralized
place where settings become "described" (setup_interactively in
the case of rototiller).

Now a GUI frontend (like glimmer) would just provide its own
setup_interactively() equivalent for constructing its widgets for
a given *_setup() method's chain of returned descs.  Whereas in
the past this wasn't really feasible unless there was never going
to be pre-supplied settings.

I suspect the til_setting_desc_check() integration into
setup_interactively() needs more work, but I think this is good
enough for now and I'm out of spare time for the moment.

1 files changed, 8 insertions, 8 deletions

diff --git a/src/drm_fb.c b/src/drm_fb.c
index 3bd7d0d..69dd3b8 100644
--- a/src/drm_fb.c
+++ b/src/drm_fb.c
@@ -68,7 +68,7 @@ static const char * connector_type_name(uint32_t type) {
 }
 
 
-static int dev_desc_generator(void *setup_context, til_setting_desc_t **res_desc)
+static int dev_desc_generator(void *setup_context, const til_setting_desc_t **res_desc)
 {
 	return  til_setting_desc_clone(&(til_setting_desc_t){
 					.name = "DRM Device Path",
@@ -145,7 +145,7 @@ static void free_strv(const char **strv)
 }
 
 
-static int connector_desc_generator(void *setup_context, til_setting_desc_t **res_desc)
+static int connector_desc_generator(void *setup_context, const til_setting_desc_t **res_desc)
 {
 	drm_fb_setup_t	*s = setup_context;
 	const char	**connectors;
@@ -254,7 +254,7 @@ _out:
 }
 
 
-static int mode_desc_generator(void *setup_context, til_setting_desc_t **res_desc)
+static int mode_desc_generator(void *setup_context, const til_setting_desc_t **res_desc)
 {
 	drm_fb_setup_t	*s = setup_context;
 	const char	**modes;
@@ -283,7 +283,7 @@ static int mode_desc_generator(void *setup_context, til_setting_desc_t **res_des
 /* setup is called repeatedly as settings is constructed, until 0 is returned. */
 /* a negative value is returned on error */
 /* positive value indicates another setting is needed, described in next_setting */
-static int drm_fb_setup(const til_settings_t *settings, til_setting_desc_t **next_setting)
+static int drm_fb_setup(const til_settings_t *settings, const til_setting_t **res_setting, const til_setting_desc_t **res_desc)
 {
 	drm_fb_setup_t			context = {};
 	til_setting_desc_generator_t	generators[] = {
@@ -305,7 +305,7 @@ static int drm_fb_setup(const til_settings_t *settings, til_setting_desc_t **nex
 	if (!drmAvailable())
 		return -ENOSYS;
 
-	return til_settings_apply_desc_generators(settings, generators, nelems(generators), &context, next_setting);
+	return til_settings_apply_desc_generators(settings, generators, nelems(generators), &context, res_setting, res_desc);
 }
 
 
@@ -351,19 +351,19 @@ static int drm_fb_init(const til_settings_t *settings, void **res_context)
 		goto _err;
 	}
 
-	dev = til_settings_get_value(settings, "dev");
+	dev = til_settings_get_value(settings, "dev", NULL);
 	if (!dev) {
 		r = -EINVAL;
 		goto _err;
 	}
 
-	connector = til_settings_get_value(settings, "connector");
+	connector = til_settings_get_value(settings, "connector", NULL);
 	if (!connector) {
 		r = -EINVAL;
 		goto _err;
 	}
 
-	mode = til_settings_get_value(settings, "mode");
+	mode = til_settings_get_value(settings, "mode", NULL);
 	if (!mode) {
 		r = -EINVAL;
 		goto _err;