On Mon, Sep 26, 2022 at 01:17:52PM +0200, Thomas Zimmermann wrote: > Hi > > Am 26.09.22 um 12:34 schrieb Geert Uytterhoeven: > > Hi Maxime, > > > > On Mon, Sep 26, 2022 at 12:17 PM Maxime Ripard <maxime@xxxxxxxxxx> wrote: > > > On Fri, Sep 23, 2022 at 11:05:48AM +0200, Thomas Zimmermann wrote: > > > > > + /* 63.556us * 13.5MHz = 858 pixels */ > > > > > > > > I kind of get what the comment wants to tell me, but the units don't add up. > > > > > > I'm not sure how it doesn't add up? > > > > > > We have a frequency in Hz (equivalent to s^-1) and a duration in s, so > > > the result ends up with no dimension, which is to be expected for a > > > number of periods? > > > > To make the units add up, it should be 13.5 Mpixel/s > > (which is what a pixel clock of 13.5 MHz really means ;-) > > Sort of. It leaves the time value as a magic number, which obfuscates what's > happening. > > The unit for htotal is pixels/scanline because if you multiply it with the > number of scanlines per frame (which is in vtotal), you get pixels/frame. > Multiplying with the frames per second results in the pixel clock in > pixels/second. That's true, but both are true? > That's a bit much for this comment. Hence, I suggested to remove these > comments entirely and document the relation among the numbers in a more > prominent location. The documentation for drm_display_mode would be a good > place, I guess. I'm not sure I understand what it's about. It's an explicit requirement of PAL and NTSC, why would something so specific be in the generic definition of drm_display_mode? Maxime
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