snd_pcm_hw_c...raint_single(9)

💅 NAME 💅

snd_pcm_hw_c...raint_single — constrain parameter to a single value

okay so bestie, welcome to the Kernel API Manual ✨ (yes that's the manual we're in, and yes it's a whole vibe). This page is about one little function that does exactly one thing and does it iconically: it pins a parameter down to one single value. No range, no "eh somewhere in between", just this value, periodt. 💅

---

✨ SYNOPSIS ✨

int snd_pcm_hw_constraint_single (struct snd_pcm_runtime *runtime ,
snd_pcm_hw_param_t var , unsigned int val );

that's it, that's the whole signature 🫶 (and yeah, the spacing there is exactly how the page shows it — we don't touch it, we respect it)

---

🎀 ARGUMENTS 🎀

• runtime — the PCM runtime instance 🌀 like, the actual live object this whole thing is running on, main character energy
• var — the hw_params variable you're constraining 🔒 the thing you're about to lock in
• val — the value you're constraining it to 🎯 the one and only answer bestie

---

⭐ RETURN ⭐

So what comes back? Depends on the vibe check 👑

• Positive → if the value is changed 🔥
• Zero → if it's not changed 🙈
• Negative → that's an error code, and no, that's not a slay 💀

---

🦋 SEE ALSO 🦋

Kernel file ./include/sound/pcm.h — that's the one, go look 🧚

and like, literally the entire PCM friend group shows up here, no cap:

• snd_pcm_stream_linked(9)
• snd_pcm_stream_lock_irqsave(9)
• snd_pcm_stream_lock_irqsave_nested(9)
• snd_pcm_group_for_each_entry(9)
• snd_pcm_running(9)
• __snd_pcm_set_state(9)
• bytes_to_samples(9)
• bytes_to_frames(9)
• samples_to_bytes(9)
• frames_to_bytes(9)
• frame_aligned(9)
• snd_pcm_lib_buffer_bytes(9)
• snd_pcm_lib_period_bytes(9)
• snd_pcm_playback_avail(9)
• snd_pcm_capture_avail(9)
• snd_pcm_playback_hw_avail(9)
• snd_pcm_capture_hw_avail(9)
• snd_pcm_playback_ready(9)
• snd_pcm_capture_ready(9)
• snd_pcm_playback_data(9)
• snd_pcm_playback_empty(9)
• snd_pcm_capture_empty(9)
• snd_pcm_trigger_done(9)
• params_channels(9)
• params_rate(9)
• params_period_size(9)
• params_periods(9)
• params_buffer_size(9)
• params_buffer_bytes(9)
• snd_pcm_format_cpu_endian(9)
• snd_pcm_set_sync(9)
• snd_pcm_set_runtime_buffer(9)
• snd_pcm_gettime(9)
• snd_pcm_set_fixed_buffer(9)
• snd_pcm_set_fixed_buffer_all(9)
• snd_pcm_sgbuf_get_addr(9)
• snd_pcm_sgbuf_get_chunk_size(9)
• snd_pcm_limit_isa_dma_size(9)
• snd_pcm_direction_name(9)
• snd_pcm_stream_str(9)
• snd_pcm_chmap_substream(9)
• pcm_format_to_bits(9)
• pcm_for_each_format(9)

---

ngl the whole "positive / zero / negative" return thing is the important bit — check it, don't assume it, or you'll be debugging at 3am crying 😭

---

okay that's the page!! 🌸 source lives under ./include/sound and this cutie is dated October 2026 — so like, it's from the future, we stan a timeless icon 👑💜 bye bestie, go constrain some parameters 🫶