sas_find_bcast_dev(9)

💅 sas_find_bcast_dev(9) — like, the Kernel API Manual one, bestie

okay so real quick before we dive in: this is a page from the Kernel API Manual, and the function we're obsessing over is sas_find_bcast_dev ✨. Strap in, she's a little niche but honestly iconic once you get her.

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🎀 NAME 🎀

sas_find_bcast_dev — literally just: find the device that was like "hey. something changed" and issued BROADCAST(CHANGE). That's it. That's the whole vibe 🫶

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🌸 SYNOPSIS 🌸

int sas_find_bcast_dev (struct domain_device *dev , struct domain_device
**src_dev );

one function, two pointer args, returns an int. no cap, that's the whole signature 💖

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🦋 ARGUMENTS 🦋

• dev — the domain device that we're gonna detect, bestie. this is your starting point, the thing you're snooping on 👀
• src_dev — aaaand this is the output: the device that originated the BROADCAST(CHANGE). the main character of the broadcast, if you will ✨

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💅 DESCRIPTION 💅

Alright so gather round, because this one's giving ✨protocol lore✨.

This whole thing exists to add self-configuration expander support. Let me paint the picture for you 🌈: imagine two expanders cascading — level one and level two, chained up. Now say the first-level expander is self-configuring, and you go and hotplug some disks into the second-level expander. What happens? Well, BROADCAST(CHANGE) doesn't just originate in the second-level expander — nope — it also originates in the first-level expander too 😭 (see SAS protocol SAS 2r-14, 7.11 for the full detail, iykyk).

Which is to say: the expander changed count in both level expanders will each increment at least once 🔥. But — and this is the plot twist — the phy whose change count actually changed? That's the source device. That's the one we actually care about 💖. Periodt.

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⭐ SEE ALSO ⭐

• Kernel file ./drivers/scsi/libsas/sas_expander.c — go read the source, it's right there 🧚

and the whole friend group:

• sas_ex_discover_devices(9)
• sas_configure_parent(9)
• sas_configure_routing(9)
• sas_discover_expander(9)
• sas_rediscover(9)
• sas_ex_revalidate_domain(9)

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ok that's the whole page 🎀 everything you need, nothing you don't. go forth and find those broadcast devices, bestie 💜

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and finally, mwah 💋 — this lil masterpiece lives in ./drivers/scsi/libsas, dated October 2026. slay 💅✨