On Mon, Oct 27, 2025 at 01:10:23PM -0400, Frank Li wrote:
> On Mon, Oct 27, 2025 at 03:19:27AM +0200, Laurent Pinchart wrote:
> > On Thu, Aug 21, 2025 at 04:15:37PM -0400, Frank Li wrote:
> > > Add helper v4l_get_required_align_by_bpp() to help get width alignment
> > > requirement. Basic replace below logic and enhance to any 2^[0..31] in
> > > drivers/media/platform/nxp/imx-mipi-csis.c
> > >
> > > mipi_csis_set_fmt(
> > > {
> > > ...
> > >
> > > switch (csis_fmt->width % 8) {
> > > case 0:
> > > align = 0;
> > > break;
> > > case 4:
> > > align = 1;
> > > break;
> > > case 2:
> > > case 6:
> > > align = 2;
> > > break;
> > > default:
> > > /* 1, 3, 5, 7 */
> > > align = 3;
> > > break;
> > > }
> > > ...
> > > }
> > >
> > > Signed-off-by: Frank Li <Frank.Li@nxp.com>
> > > ---
> > > The same patch will be see at https://lore.kernel.org/imx/20250729-imx8qxp_pcam-v4-2-4dfca4ed2f87@nxp.com/
> > > dw csi2 patch also this
> > > ---
> > > include/media/v4l2-common.h | 30 ++++++++++++++++++++++++++++++
> > > 1 file changed, 30 insertions(+)
> > >
> > > diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h
> > > index 39dd0c78d70f7b935c2e10f9767646d2cedd3079..0a9da5e8daaddf26903d9ff4bed08b283dcd38b2 100644
> > > --- a/include/media/v4l2-common.h
> > > +++ b/include/media/v4l2-common.h
> > > @@ -704,4 +704,34 @@ static inline bool v4l2_is_quant_valid(__u8 quantization)
> > > quantization == V4L2_QUANTIZATION_LIM_RANGE;
> > > }
> > >
> > > +/**
> > > + * v4l_get_required_align_by_bpp - get align requirement for
> > > + * v4l_bound_align_image(). (bpp * width) % (1 << align) have to be 0.
> > > + * given number bpp, get width's alignment requirement. For example,
> > > + * if align is 3, means require bpp * width must be multiples of 8.
> > > + * bpp return width's requirememnt
> > > + * 0 0 none
> > > + * 1 3 8 (need 3 zero bits)
> > > + * 2 2 4
> > > + * 3 3 8
> > > + * 4 1 2
> > > + * 5 3 8
> > > + * 6 2 4
> > > + * 7 3 8
> >
> > This is supposed to be a brief one-line description. The rest of the
> > documentation goes after the argument.
> >
> > Also, have checked the formatting of the generated documentation ?
> >
> > > + * @bpp: input bpp
> >
> > I have no idea if this is a bits per pixel or bytes per pixel value. I'm
> > actually not sure what the function is even supposed to do. It feels
> > it's really a ad-hoc helper, I would like to see it being used in
> > multiple drivers to see if it makes sense.
>
> drivers/media/platform/nxp/imx-mipi-csis.c
> imx_cpi_set_fmt() in
> https://lore.kernel.org/imx/20250729-imx8qxp_pcam-v4-3-4dfca4ed2f87@nxp.com/
>
> I am not sure if userspace to pass down a old width to driver, like 1033.
Do you agree this change, I can post this patch + imx-mipi-csis.c as
sperate patches?
dwc csi2 need split more small serise to reduce review efforts.
Frank
>
> Frank
>
> >
> > > + * @align: expected alignment, 2^(align).
> > > + *
> > > + * return: required alignment.
> > > + */
> > > +static inline u32 v4l_get_required_align_by_bpp(u32 bpp, u32 align)
> > > +{
> > > + int pos;
> > > +
> > > + if (bpp == 0)
> > > + return 0;
> > > +
> > > + pos = ffs(bpp) - 1;
> > > + return pos > align ? 0 : align - pos;
> > > +}
> > > +
> > > #endif /* V4L2_COMMON_H_ */
> > >
> >
> > --
> > Regards,
> >
> > Laurent Pinchart