Re: [PATCH v2 2/2] media: i2c: ov02e10: add OV02E10 image sensor driver

[Bryan O'Donoghue]

On 01/04/2025 03:35, Alan Stern wrote:
> On Tue, Apr 01, 2025 at 01:34:29AM +0100, Bryan O'Donoghue wrote:
> > On 27/03/2025 07:36, Sakari Ailus wrote:
> > > > +static u64 to_pixel_rate(u32 f_index)
> > > > +{
> > > > +	u64 pixel_rate = link_freq_menu_items[f_index] * 2 * OV02E10_DATA_LANES;
> > > > +
> > > > +	do_div(pixel_rate, OV02E10_RGB_DEPTH);
> > > The pixel rate control is for the pixel rate on the pixel array, not on the
> > > CSI-2 interface. Without binning or sub-sampling these may the same still,
> > > but this only works in special cases really.
> >
> > Hmm computer says no, I don't think I have understood this comment..
> >
> > Looking at other drivers, I'd say the above pattern is pretty common -
> > taking ov8856 as an example that's pretty much equivalent logic to the
> > above, ov08x40 does something similar.
> >
> > =>
> >
> > pixel_rate == link_freq * 2 * #oflanes / RGB_DEPTH
> >             => 360MHz * 2 * 2 / 10
> >             => 360000000 * 2 * 2 / 10
> >             => 144000000
> >
> > If I'm understanding you though you mean the pixel rate for the control
> > V4L2_CID_PIXEL_RATE expressed here should be the resolution * the FPS /
> > bits_per_pixel
> >
> > pixel_rate = wdith x height x fps / bpp
> >             => 1928 * 1088 * 30 / 10
> >             => 6292992
> >
> > i.e. the pixel rate not related to the CSI2 link frequency ?
>
> I know practically nothing about this stuff, but even I can see that this
> suggestion doesn't make sense:
>
> 	width x height = pixels per frame;
> 	pixels per frame x fps = pixels per second;
> 	pixels per second / bits per pixel = pixels^2 / (bits x seconds)
>
> which is meaningless.  If the division were replaced with a
> multiplication this would become:
>
> 	pixels per second x bits per pixel = bits per second
>
> which at least is reasonable.
>
> Alan

TBH Perplexity.ai gave me that answer, my question is still are we 
saying the upstream examples are wrong here or have I just not 
understood the original comment ?

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bod