sdca_ump_write_message(9)

💌 sdca_ump_write_message(9) — bestie's guide to the Kernel API Manual ✨

okay so this is the page for sdca_ump_write_message, and no cap, it's literally the "write a UMP message to the device" girlie. that's the whole NAME vibe 🎀

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🌸 SYNOPSIS 🌸

int sdca_ump_write_message (struct device *dev , struct regmap
*device_regmap , struct regmap *function_regmap , struct
sdca_function_data *function , struct sdca_entity *entity , unsigned int
offset_sel , unsigned int msg_offset , unsigned int length_sel , void
*msg , int msg_len );

look at her. ten parameters. main character energy fr fr 💅

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✨ ARGUMENTS ✨

okay bestie, let's meet the cast 🫶

• dev — Pointer to the struct device used for error messages. like, when things go wrong, this is who gets to complain about it 😭
• device_regmap — Pointer to the Device register map. iconic. essential. hold onto her 🔥
• function_regmap — Pointer to the regmap for the SDCA Function. yes she's a different regmap from the device one, don't mix them up bestie 🙈
• function — Pointer to the Function information.
• entity — Pointer to the SDCA Entity.
• offset_sel — Control Selector for the UMP Offset Control.
• msg_offset — Offset within the UMP buffer at which the message should be written. like, where exactly in the buffer we're placing her 💅
• length_sel — Control Selector for the UMP Length Control.
• msg — Pointer to the data that should be written to the UMP buffer.
• msg_len — Length of the message data in bytes. count them bytes, queen 🍓

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🦋 DESCRIPTION 🦋

okay so the order of operations here is not optional, bestie — the way this works is a whole little three-step routine and you gotta do it in order 🌈

1. The caller should first call sdca_ump_get_owner_host to ensure the host currently owns the UMP buffer. got it? host owns the buffer first. periodt 👑
2. Then this function — sdca_ump_write_message — can be used to write a message. that's her moment. that's her whole job ✨
3. Finally, sdca_ump_set_owner_device should be called to return the buffer to the device, allowing the device to access the message. you must hand it back, otherwise the device can't see the message you just wrote 😭

lowkey the whole arc is: check ownership → write → hand back. skip a step and it's giving chaos 💀

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💖 RETURN 💖

• Returns zero on success 😌✨
• and a negative error code on failure 😭

that's it. zero = slay, negative = not slay. iykyk 🎀

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🧚 SEE ALSO 🧚

• Kernel file ./sound/soc/sdca/sdca_ump.c
• sdca_ump_get_owner_host(9)
• sdca_ump_set_owner_device(9)
• sdca_ump_read_message(9)

like the whole friend group honestly, go read them all 🫶

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💜 and that's the page!! source/version vibes: this one lives in ./sound/soc/sdca, dated October 2026, and it's sdca_ump_write_message(9) — the manual header up top and this footer are the whole official package, so now you know exactly where she came from. bye bestie, go write some UMP messages responsibly 🌸✨🦋