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-rw-r--r--drivers/media/video/v4l2-common.c75
-rw-r--r--include/media/v4l2-common.h10
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_ */