[PATCH v2 1/3] drm/modes: introduce drm_mode_validate_mode() helper function

[Sean Nyekjaer]

On Tue, Nov 26, 2024 at 01:09:10PM +0100, Maxime Ripard wrote:
> On Tue, Nov 26, 2024 at 12:34:26PM +0100, Sean Nyekjaer wrote:
> > Hi,
> > 
> > On Tue, Nov 26, 2024 at 09:38:55AM +0100, Maxime Ripard wrote:
> > > Hi,
> > > 
> > > On Tue, Nov 26, 2024 at 08:36:00AM +0100, Sean Nyekjaer wrote:
> > > > On Mon, Nov 25, 2024 at 05:00:56PM +0100, Maxime Ripard wrote:
> > > > > On Mon, Nov 25, 2024 at 02:49:26PM +0100, Sean Nyekjaer wrote:

[...]

> > > > > 
> > > > > Thanks a lot for doing that!
> > > > > 
> > > > > I wonder about the naming though (and prototype). I doesn't really
> > > > > validates a mode, but rather makes sure that a given rate is a good
> > > > > approximation of a pixel clock. So maybe something like
> > > > > drm_mode_check_pixel_clock?
> > > > 
> > > > Naming is hard :) I will use drm_mode_check_pixel_clock() for V2.
> > > > 
> > > > Would it make sense to have the pixel clock requirement as a input
> > > > parameter? For HDMI it is 0.5%
> > > 
> > > This code was only used for panels so far. It reuses the same tolerance
> > > than HDMI because we couldn't come up with anything better, but it
> > > should totally apply to other things.
> > > 
> > > > and in my case the LVDS panel 10%.
> > > 
> > > 10% is a lot, and I'm not sure we'll want that. The framerate being
> > > anywhere between 54 and 66 fps will trip a lot of applications too.
> > > 
> > > Why do you need such a big tolerance?
> > 
> > I don't need it, it was just from the datasheet for the LVDS panel :)
> 
> So you mean the panel accepts a pixel clock within +/- 10%?

Yes :)

> 
> That makes sense, but then we should also adjust the mode timings to
> match so we still keep 60fps. There's much more to *that* than the
> helpers you try to create though, so let's keep it aside for now.

Ok

> 
> Maxime

/Sean