On Fri, Jul 10, 2026 at 01:27:37PM +0300, Cristian Ciocaltea wrote: > On 7/8/26 1:11 PM, Cristian Ciocaltea wrote: > > Hi Maxime, > > > > On 7/7/26 7:10 PM, Maxime Ripard wrote: > >> On Fri, Jul 03, 2026 at 10:31:55PM +0300, Cristian Ciocaltea wrote: > >>> Hi Dmitry, > >>> > >>> Thanks for your quick review! > >>> > >>> On 7/3/26 5:05 PM, Dmitry Baryshkov wrote: > >>>> On Thu, Jul 02, 2026 at 05:46:15PM +0300, Cristian Ciocaltea wrote: > >>>>> In preparation for adding HDMI 2.x source capabilities, introduce struct > >>>>> drm_connector_hdmi_caps and a new drmm_connector_hdmi_init_with_caps() > >>>>> helper. > >>>>> > >>>>> The existing drmm_connector_hdmi_init() helper currently takes > >>>>> individual capability arguments such as supported_formats and max_bpc. > >>>>> Adding more HDMI-specific arguments to that function would not scale > >>>>> well, so move those values into a dedicated capabilities structure and > >>>>> implement the existing helper as a wrapper around the new caps-based > >>>>> interface. > >>>> > >>>> I think, it was an intention of Maxime: make sure that every driver is > >>>> forced to provide some values here. With the struct-based init it is > >>>> easy to overlook or to ommit a value. > >>> > >>> Agreed that the struct-based init loses the compile-time guarantee that > >>> every > >>> argument is explicitly provided - that's a real downside. > >>> > >>> I'd argue it's recoverable, though: the init helper validates the > >>> mandatory > >>> fields, so a driver that omits a required value gets rejected at init time > >>> rather than silently misconfigured. The "you must provide sane values" > >>> property > >>> is expected to be preserved, just enforced at runtime instead of by the > >>> compiler. > >> > >> Yeah, I don't think we can win with C here. Rust might, but we're > >> probably a long way from that. > >> > >>> The main motivation for the struct is scalability/maintainability as we > >>> add HDMI > >>> 2.x capabilities: new fields go into the struct rather than growing the > >>> helper's > >>> argument list, so existing callers don't need churny signature updates on > >>> every > >>> extension. > >>> > >>> FWIW, in the previous revision we discussed addressing the concern with a > >>> callback instead. Sadly, I had to discard that approach, as it proved not > >>> flexible enough, e.g. drm_bridge_connector_init() computes caps > >>> dynamically, and > >>> would have required either stateful callbacks, or storing > >>> redundant/temporary > >>> cap data in driver-private structures just to satisfy the callback. > >> > >> I just realized something reviewing your patch: we don't necessarily > >> need an extra argument or a callback, we can just put these fields into > >> drm_hdmi_connector_funcs directly, and then validate them in init. > > > > If I understand correctly, we should drop the drm_connector_hdmi_caps struct > > introduced by this patch and move all its fields into > > drm_hdmi_connector_funcs. > > > > In that case, how should we proceed with drmm_connector_hdmi_init()? > > Actually, this brings us to the callback issue: we cannot compute caps > dynamically, as it only works with static data, since funcs is supposed to be > immutable.
Does it? The core and helpers must consider it immutable but it doesn't have to. drm_bridge_connector for example could totally allocate it and dynamically create it based on the bridge capabilities. > Moreover, we would end up with some redundancy, as most of these input fields, > after validation, would be stored (altered or not) directly in > drm_connector/drm_connector_hdmi structs. I mean, part of the conversion would obviously be to remove the redundant fields.
signature.asc
Description: PGP signature
