diff options
| -rw-r--r-- | drivers/media/video/v4l2-common.c | 75 | ||||
| -rw-r--r-- | include/media/v4l2-common.h | 10 |
2 files changed, 84 insertions, 1 deletions
diff --git a/drivers/media/video/v4l2-common.c b/drivers/media/video/v4l2-common.c index e7b443c116f..1ebbe738019 100644 --- a/drivers/media/video/v4l2-common.c +++ b/drivers/media/video/v4l2-common.c @@ -1021,4 +1021,77 @@ const unsigned short *v4l2_i2c_tuner_addrs(enum v4l2_i2c_tuner_type type) } EXPORT_SYMBOL_GPL(v4l2_i2c_tuner_addrs); -#endif +/* Clamp x to be between min and max, aligned to a multiple of 2^align. min + * and max don't have to be aligned, but there must be at least one valid + * value. E.g., min=17,max=31,align=4 is not allowed as there are no multiples + * of 16 between 17 and 31. */ +static unsigned int clamp_align(unsigned int x, unsigned int min, + unsigned int max, unsigned int align) +{ + /* Bits that must be zero to be aligned */ + unsigned int mask = ~((1 << align) - 1); + + /* Round to nearest aligned value */ + if (align) + x = (x + (1 << (align - 1))) & mask; + + /* Clamp to aligned value of min and max */ + if (x < min) + x = (min + ~mask) & mask; + else if (x > max) + x = max & mask; + + return x; +} + +/* Bound an image to have a width between wmin and wmax, and height between + * hmin and hmax, inclusive. Additionally, the width will be a multiple of + * 2^walign, the height will be a multiple of 2^halign, and the overall size + * (width*height) will be a multiple of 2^salign. The image may be shrunk + * or enlarged to fit the alignment constraints. + * + * The width or height maximum must not be smaller than the corresponding + * minimum. The alignments must not be so high there are no possible image + * sizes within the allowed bounds. wmin and hmin must be at least 1 + * (don't use 0). If you don't care about a certain alignment, specify 0, + * as 2^0 is 1 and one byte alignment is equivalent to no alignment. If + * you only want to adjust downward, specify a maximum that's the same as + * the initial value. + */ +void v4l_bound_align_image(u32 *w, unsigned int wmin, unsigned int wmax, + unsigned int walign, + u32 *h, unsigned int hmin, unsigned int hmax, + unsigned int halign, unsigned int salign) +{ + *w = clamp_align(*w, wmin, wmax, walign); + *h = clamp_align(*h, hmin, hmax, halign); + + /* Usually we don't need to align the size and are done now. */ + if (!salign) + return; + + /* How much alignment do we have? */ + walign = __ffs(*w); + halign = __ffs(*h); + /* Enough to satisfy the image alignment? */ + if (walign + halign < salign) { + /* Max walign where there is still a valid width */ + unsigned int wmaxa = __fls(wmax ^ (wmin - 1)); + /* Max halign where there is still a valid height */ + unsigned int hmaxa = __fls(hmax ^ (hmin - 1)); + + /* up the smaller alignment until we have enough */ + do { + if (halign >= hmaxa || + (walign <= halign && walign < wmaxa)) { + *w = clamp_align(*w, wmin, wmax, walign + 1); + walign = __ffs(*w); + } else { + *h = clamp_align(*h, hmin, hmax, halign + 1); + halign = __ffs(*h); + } + } while (halign + walign < salign); + } +} +EXPORT_SYMBOL_GPL(v4l_bound_align_image); +#endif /* defined(CONFIG_I2C) */ diff --git a/include/media/v4l2-common.h b/include/media/v4l2-common.h index 95f4364322e..33a18426ab9 100644 --- a/include/media/v4l2-common.h +++ b/include/media/v4l2-common.h @@ -209,4 +209,14 @@ struct v4l2_routing { u32 output; }; +/* ------------------------------------------------------------------------- */ + +/* Miscellaneous helper functions */ + +void v4l_bound_align_image(unsigned int *w, unsigned int wmin, + unsigned int wmax, unsigned int walign, + unsigned int *h, unsigned int hmin, + unsigned int hmax, unsigned int halign, + unsigned int salign); + #endif /* V4L2_COMMON_H_ */ |