video: pixel_format: Add compare helpers

Add helpers that compare two pixel-format descriptions against
each other.

Signed-off-by: Thomas Zimmermann <[e-mail]>
Reviewed-by: Javier Martinez Canillas <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]

include/video/pixel_format.h

···
 #define PIXEL_FORMAT_XRGB2101010 \
 	{ 32, false, { .alpha = {0, 0}, .red = {20, 10}, .green = {10, 10}, .blue = {0, 10} } }
 
+#define __pixel_format_cmp_field(lhs, rhs, name) \
+	{ \
+		int ret = ((lhs)->name) - ((rhs)->name); \
+		if (ret) \
+			return ret; \
+	}
+
+#define __pixel_format_cmp_bitfield(lhs, rhs, name) \
+	{ \
+		__pixel_format_cmp_field(lhs, rhs, name.offset); \
+		__pixel_format_cmp_field(lhs, rhs, name.length); \
+	}
+
+/**
+ * pixel_format_cmp - Compares two pixel-format descriptions
+ *
+ * @lhs: a pixel-format description
+ * @rhs: a pixel-format description
+ *
+ * Compares two pixel-format descriptions for their order. The semantics
+ * are equivalent to memcmp().
+ *
+ * Returns:
+ * 0 if both arguments describe the same pixel format, less-than-zero if lhs < rhs,
+ * or greater-than-zero if lhs > rhs.
+ */
+static inline int pixel_format_cmp(const struct pixel_format *lhs, const struct pixel_format *rhs)
+{
+	__pixel_format_cmp_field(lhs, rhs, bits_per_pixel);
+	__pixel_format_cmp_field(lhs, rhs, indexed);
+
+	if (lhs->indexed) {
+		__pixel_format_cmp_bitfield(lhs, rhs, index);
+	} else {
+		__pixel_format_cmp_bitfield(lhs, rhs, alpha);
+		__pixel_format_cmp_bitfield(lhs, rhs, red);
+		__pixel_format_cmp_bitfield(lhs, rhs, green);
+		__pixel_format_cmp_bitfield(lhs, rhs, blue);
+	}
+
+	return 0;
+}
+
+/**
+ * pixel_format_equal - Compares two pixel-format descriptions for equality
+ *
+ * @lhs: a pixel-format description
+ * @rhs: a pixel-format description
+ *
+ * Returns:
+ * True if both arguments describe the same pixel format, or false otherwise.
+ */
+static inline bool pixel_format_equal(const struct pixel_format *lhs,
+				      const struct pixel_format *rhs)
+{
+	return !pixel_format_cmp(lhs, rhs);
+}
+
 #endif