Re: [RFC] ivshmem v2: Shared memory device specification

[Michael S. Tsirkin]

On Mon, May 25, 2020 at 09:58:28AM +0200, Jan Kiszka wrote:
> #### Vendor Specific Capability (ID 09h)
> 
> This capability must always be present.
> 
> | Offset | Register            | Content                                      
>   |
> |-------:|:--------------------|:-----------------------------------------------|
> |    00h | ID                  | 09h                                          
>   |
> |    01h | Next Capability     | Pointer to next capability or 00h            
>   |
> |    02h | Length              | 20h if Base Address is present, 18h 
> otherwise  |
> |    03h | Privileged Control  | Bit 0 (read/write): one-shot interrupt mode  
>   |
> |        |                     | Bits 1-7: Reserved (0 on read, writes 
> ignored) |
> |    04h | State Table Size    | 32-bit size of read-only State Table         
>   |
> |    08h | R/W Section Size    | 64-bit size of common read/write section     
>   |
> |    10h | Output Section Size | 64-bit size of output sections               
>   |
> |    18h | Base Address        | optional: 64-bit base address of shared 
> memory |
> 
> All registers are read-only. Writes are ignored, except to bit 0 of
> the Privileged Control register.


Is there value in making this follow the virtio vendor-specific
capability format? That will cost several extra bytes - do you envision
having many of these in the config space?
Also, do we want to define an extended capability format in case this
is a pci extended capability?

-- 
MST