On Mon, Nov 07, 2022 at 12:29:28PM +0100, Noralf Trønnes wrote: > > > Den 07.11.2022 11.21, skrev Maxime Ripard: > > Hi Noralf, > > > > I'll leave aside your comments on the code, since we'll use your implementation. > > > > On Sun, Nov 06, 2022 at 05:33:48PM +0100, Noralf Trønnes wrote: > >> Den 26.10.2022 17.33, skrev maxime@xxxxxxxxxx: > >>> + > >>> + if (cmdline->tv_mode_specified) > >>> + default_mode = cmdline->tv_mode; > >> > >> I realised that we don't verify tv_mode coming from the command line, > >> not here and not in the reset helper. Should we do that? A driver should > >> be programmed defensively to handle an illegal/unsupported value, but it > >> doesn't feel right to allow an illegal enum value coming through the > >> core/helpers. > > > > I don't think we can end up with an invalid value here if it's been > > specified. > > > > We parse the command line through drm_mode_parse_tv_mode() (introduced > > in patch 13 "drm/modes: Introduce the tv_mode property as a command-line > > option") that will pick the tv mode part of the command line, and call > > drm_get_tv_mode_from_name() using it. > > > > drm_get_tv_mode_from_name() will return a EINVAL if it's not a value we > > expect, and mode->tv_mode is only set on success. And AFAIK, there's no > > other path that will set tv_mode. > > > > I see now that illegal was the wrong word, but if the driver only > supports ntsc, the user can still set tv_mode=PAL right? And that's an > unsupported value that the driver can't fulfill, so it errors out. But > then again maybe that's just how it is, we can also set a display mode > that the driver can't handle, so this is no different in that respect. > Yeah, my argument lost some of its strength here :) I don't think we can handle this better, really. Falling back to NTSC in that case would really be a stretch: it's a different mode, with a different TV mode, etc. It's an even bigger stretch than picking another mode I guess, and like you said we're not doing that if the mode isn't supported Maxime
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