Hi, On Tue, Feb 27, 2024 at 09:51:06AM +0000, Simon Ser wrote: > On Monday, February 26th, 2024 at 18:23, Dave Stevenson <dave.stevenson@xxxxxxxxxxxxxxx> wrote: > > > and I've also completely missed any kernel command line > > > arguments manipulating KMS properties. > > > > "tv_mode" on the command line is handled in > > drm_mode_parse_cmdline_options() [3], as are rotate, reflect_x, > > reflect_y, margin_[left|right|top|bottom], and panel_orientation all > > to set the relevant KMS properties. > > > > Having "video=Composite-1:PAL,tv_mode=Mono" on the kernel command line > > will set up connector Composite-1 with the standard 720x576 50Hz > > interlaced timings, and DRM_MODE_TV_MODE_MONOCHROME selected on the > > tv_mode property. Swap in different tv_mode descriptions as required > > (eg PAL,tv_mode=SECAM), although some make little sense. > > > > That's the main route I'm looking at for configuring this property, > > for situations such as having a black and white TV connected. You > > don't get the opportunity to interrogate a composite display over what > > it supports, so it has to be configured manually somewhere in the > > system. If your monitor doesn't support the system default, then you > > can't see a GUI in order to change the option, and there is no > > guaranteed supported configuration so the command line is about the > > only option. > > > > The use cases for runtime switching of the "tv_mode" are exceedingly > > rare, so IMHO the property doesn't need exposing through the UAPI. > > However it was added to the UAPI about 8 years ago for vc4 and sunxi, > > and is also now used by other drivers, so can't be reverted. Does that > > mean it can now never be changed without jumping through the hoop of > > creating some userspace user? > > I don't know what the rules were 8 years ago, but the current uAPI rules > are what they are, and a new enum entry is new uAPI. TBF, and even if the wayland compositors support is missing, this property is perfectly usable as it is with upstream, open-source code, through either the command-line or X.org, and it's documented. So it's fine by me from a UAPI requirement side. Maxime
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