drivers/gpu/drm/amd/display/dc/basics/custom_float.c

Source file repositories/reference/linux-study-clean/drivers/gpu/drm/amd/display/dc/basics/custom_float.c

File Facts

System
Linux kernel
Corpus path
drivers/gpu/drm/amd/display/dc/basics/custom_float.c
Extension
.c
Size
4230 bytes
Lines
174
Domain
Driver Families
Bucket
drivers/gpu
Inferred role
Driver Families: implementation source
Status
source implementation candidate

Why This File Exists

Repeatable hardware-adapter layer. Deep compatibility for every driver is out of scope; this atlas records patterns, probe lifecycles, bus glue, IRQ/DMA usage, and links back to core abstractions.

Dependency Surface

Detected Declarations

Annotated Snippet

if (exp_offset <= i) {
			*mantissa = 0;
			*exponenta = 0;
			return true;
		}

		*exponenta = exp_offset - i;
	} else if (dc_fixpt_le(mantissa_constant_plus_max_fraction, value)) {
		uint32_t i = 1;

		do {
			value = dc_fixpt_shr(value, 1);
			++i;
		} while (dc_fixpt_lt(mantissa_constant_plus_max_fraction, value));

		*exponenta = exp_offset + i - 1;
	} else {
		*exponenta = exp_offset;
	}

	mantiss = dc_fixpt_sub(value, dc_fixpt_one);

	if (dc_fixpt_lt(mantiss, dc_fixpt_zero) ||
	    dc_fixpt_lt(dc_fixpt_one, mantiss))
		mantiss = dc_fixpt_zero;
	else
		mantiss = dc_fixpt_shl(mantiss, (unsigned char)format->mantissa_bits);

	*mantissa = dc_fixpt_floor(mantiss);

	return true;
}

static bool setup_custom_float(const struct custom_float_format *format,
			       bool negative,
			       uint32_t mantissa,
			       uint32_t exponenta,
			       uint32_t *result)
{
	uint32_t i = 0;
	uint32_t j = 0;
	uint32_t value = 0;

	/* verification code:
	 * once calculation is ok we can remove it
	 */

	const uint32_t mantissa_mask =
		(1 << (format->mantissa_bits + 1)) - 1;

	const uint32_t exponenta_mask =
		(1 << (format->exponenta_bits + 1)) - 1;

	if (mantissa & ~mantissa_mask) {
		BREAK_TO_DEBUGGER();
		mantissa = mantissa_mask;
	}

	if (exponenta & ~exponenta_mask) {
		BREAK_TO_DEBUGGER();
		exponenta = exponenta_mask;
	}

	/* end of verification code */

	while (i < format->mantissa_bits) {
		uint32_t mask = 1 << i;

		if (mantissa & mask)
			value |= mask;

		++i;
	}

	while (j < format->exponenta_bits) {
		uint32_t mask = 1 << j;

		if (exponenta & mask)
			value |= mask << i;

		++j;
	}

	if (negative && format->sign)
		value |= 1 << (i + j);

	*result = value;

	return true;
}

Annotation

Implementation Notes