STREAMS and Character Device Coexistence [PSARC/2009/380 FastTrack timeout 07/13/2009]

[Edward Pilatowicz]

hey garrett,
some quick questions.

- this new functionality seems to be tied to the vnode/specfs layer
  which is how userland and the ldi accesses devices, so presumably this
  streams to cb_ops fall back behaviour will be supported for both userland
  and ldi based device access?  (i assume so.)

- will this fall back behaviour be supported for CLONE_DEV based minor
  nodes?  (i assume not.)

- once a device minor node is successfully opened, the underlying driver
  must have decided on streams or cb_ops based access.  so:

	- if it decided on cb_ops accesses, will subsequent opens go
	  directly to the cb_ops open routine?  (i assume so.)

	- if it decided on streams access, is it valid for subsequent
	  open calls to return ENOSTR?  (i assume not.)

- device open/close exclusion guarantees are implemented separately for
  streams and cb_ops based access.  presumably these guarantees will
  still apply to devices that can switch between streams and cb_ops based
  accesses?  (in which case i guess the properties defined in
  PSARC/2007/310 will be applicable to streams based drivers.)

- do you anticipate having individual minor device nodes that switch
  between cb_ops and steams based access?

- instead of having the streams open entry point return ENOSTR to fall
  back to cb_ops, did you consider adding a new flag to
  ddi_create_minor_node() so that a driver could specify the desired
  access semantics of a given minor node?

- what is the commitment level of this new ENOSTR interface?

ed

On Mon, Jul 06, 2009 at 08:55:44AM -0700, Garrett D'Amore - sun microsystems wrote:
> I'm submitting the following case on my own behalf.  Times out on 7/13/2009.
> This case seeks patch binding.
> 
> Template Version: @(#)sac_nextcase 1.68 02/23/09 SMI
> This information is Copyright 2009 Sun Microsystems
> 1. Introduction
>     1.1. Project/Component Working Name:
> 	 STREAMS and Character Device Coexistence
>     1.2. Name of Document Author/Supplier:
> 	 Author:  Garrett D'Amore
>     1.3  Date of This Document:
> 	06 July, 2009
> 4. Technical Description
> 
> STREAMS and Character Device Coexistence
> ----------------------------------------
>