audio: use size_t for circular-buffer bytes counts

[softwarecki]

Change cir_buf_bytes_without_wrap() and cir_buf_bytes_without_wrap_rewind() to return size_t instead of int. Both now use uintptr_t for the pointer arithmetic. Correct doxygen comments of cir_buf_bytes_without_wrap(), cir_buf_wrap() and source_cir_buf_wrap().

In the volume module change the frames parameter, return type, and the internal byte/frame/sample counters of vol_zc_get_s16/s24/s32 (and the vol_zc_func typedef) to size_t, and make the channel count unsigned.

Switch the pointer bound-check assertions from intptr_t to uintptr_t casts. A signed comparison is incorrect for addresses crossing the 0x80000000 boundary and can silently invert the assert.

[Copilot]

🟡 Changes recommended

Signed pointer-distance arithmetic remains in circular-buffer helpers and can overflow on valid 32-bit address-boundary cases.

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Pull request overview

This PR updates circular-buffer byte accounting and volume zero-crossing interfaces to use unsigned, pointer-sized types, with related assertion and documentation fixes.

Changes:

• Uses size_t and uintptr_t for byte calculations.
• Updates volume zero-crossing counters and callback types.
• Corrects pointer assertions and Doxygen documentation.

File summaries

File	Summary
src/include/sof/audio/audio_stream.h	Updates stream pointer assertions and byte-distance handling.
src/include/module/audio/audio_stream.h	Updates circular-buffer helpers and documentation.
src/audio/volume/volume.h	Updates the zero-crossing callback signature.
src/audio/volume/volume.c	Updates zero-crossing counters and channel typing.

Review details

Suppressed comments (3)

src/include/module/audio/audio_stream.h:205

• cir_buf_wrap() is used for both source/read and sink/write pointers (for example, the output pointer in src/audio/component.c:311), so describing ptr as a read pointer is inaccurate for this generic helper. Please document it as a read-or-write pointer, as the previous API wording did.

 * Verifies the pointer and performs rollover when reaching the end of the circular buffer.
 * @param ptr Read pointer that may have moved past the buffer end.

src/include/sof/audio/audio_stream.h:824

• The rewind assertion is now unsigned, but to_begin is still computed by subtracting intptr_t addresses and storing the result in int. A valid range crossing 0x80000000 therefore passes the assertion while the subtraction can overflow and return an incorrect rewind distance. Use unsigned pointer-sized arithmetic and propagate a suitable non-negative type.

	assert((uintptr_t)ptr >= (uintptr_t)source->addr);
	int to_begin = (intptr_t)ptr - (intptr_t)source->addr;
	return to_begin;

src/include/sof/audio/audio_stream.h:841

• These checks now accept addresses on either side of 0x80000000, but the rewind results below still convert the addresses to intptr_t before subtracting. A valid rewind that crosses that sign boundary can therefore invoke signed-overflow arithmetic and return an invalid pointer. Keep the pointer-distance calculations unsigned (or use pointer arithmetic) throughout this helper.

	assert((uintptr_t)wptr >= (uintptr_t)source->addr);
	assert((uintptr_t)source->end_addr > (uintptr_t)wptr);

• Files reviewed: 4/4 changed files
• Comments generated: 1
• Review effort level: Lite

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