Re: [PATCH v2 3/5] irqchip: RISC-V Local Interrupt Controller Driver

[Christoph Hellwig]

On Mon, Sep 10, 2018 at 10:41:22PM +0530, Anup Patel wrote:
> RISC-V priv spec 1.10 defines the 9 bits in MIE and MIP registers and
> other bits are reserved.
> 
> The unused bits in MIP are WIRI (reserved write ignored and read ignored)
> and unused bits in MIE are WPRI (reserved write preserve values and
> read ignored).
> 
> The RISC-V priv spec 1.10 does not tell that unused reserved bits in
> MIE/MIP cannot be used for:
> 1. CPU implementation specific local interrupts
> 2. Per-CPU device interrupts.
> 
> The RISC-V priv spec 1.10 tries to only describe MIE/MIP bits which
> are mandatory on any RISC-V 1.10 compliant CPU but it possible to
> used other reserved bits for implementation specific local interrupts.

Reserved means reserved for future versions of the spec, not for vendor
specific bad ideas.