IPA REGISTERS(9)

💅 IPA Registers 💅

okay so bestie, this is the IPA Registers(9) page from the Kernel API Manual, and we are gonna get you comfy with it fr fr. ✨

IPA registers live inside the "ipa-reg" address space defined by Device Tree. Each register has a specified offset within that space, and that space gets mapped into virtual memory space in ipa_mem_init. Every register has a unique identifier taken from the ipa_reg_id enumerated type. All IPA registers are 32 bits wide — no cap, periodt. 💖

Certain "parameterized" register types are duplicated for a number of instances of something. For example, each IPA endpoint has a set of registers defining its configuration — iconic. The offset to an endpoint's set of registers is computed based on a "base" offset, plus an endpoint's ID multiplied by a "stride" value for the register. Similarly, some registers have an offset that depends on execution environment. In this case, the stride is multiplied by a member of the gsi_ee_id enumerated type. 🦋

Each version of IPA implements an array of ipa_reg structures indexed by register ID. Each entry in the array specifies the base offset and, for parameterized registers, a non-zero stride value. Not all versions of IPA define all registers. The offset for a register is returned by reg_offset when the register's ipa_reg structure is supplied; zero is returned for an undefined register — and that should never happen, bestie. 😭 vibe check: that zero return is a should-never-happen situation.

Some registers encode multiple fields within them. Each field in such a register has a unique identifier from an enumerated type. The position and width of the fields in a register are defined by an array of field masks, indexed by field ID. Two functions are used to access register fields, and both take an ipa_reg structure as argument. To encode a value to be represented in a register field, pass the value and field ID to reg_encode. To extract a value encoded in a register field, pass the field ID to reg_decode. In addition, for single-bit fields, reg_bit can be used either to encode the bit value or to generate a mask used to extract the bit value. 💅 iykyk

🌈 SEE ALSO 🌈

• Kernel file ./drivers/net/ipa/ipa_reg.h
• enum ipa_seq_type(9)
• enum ipa_seq_rep_type(9)
• enum ipa_irq_id(9)

byeeee 🫶 this cute little sign-off is brought to you by the ./drivers/net/ipa source/version, dated October 2026 — mwah 💋