[PATCH v3 02/31] media: v4l2-common: Add helper function v4l_get_required_align_by_bpp()
From: Frank Li <Frank.Li@nxp.com>
Date: 2025-08-21 20:16:23
Also in:
imx, linux-devicetree, linux-media, linux-phy, linux-staging, lkml
Subsystem:
media input infrastructure (v4l/dvb), the rest · Maintainers:
Mauro Carvalho Chehab, Linus Torvalds
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/ (local)
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 + * @bpp: input bpp + * @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_ */
--
2.34.1