linux-kernel - Re: [PATCH 2/4] remoteproc: introduce version element into resource type field

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Date:   Thu, 21 May 2020 10:54:21 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     Suman Anna <s-anna@...com>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Clement Leger <cleger@...ray.eu>,
        Loic Pallardy <loic.pallardy@...com>,
        Arnaud Pouliquen <arnaud.pouliquen@...com>,
        Lokesh Vutla <lokeshvutla@...com>,
        linux-remoteproc@...r.kernel.org, devicetree@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/4] remoteproc: introduce version element into resource
 type field

On Wed 25 Mar 13:46 PDT 2020, Suman Anna wrote:

> The current remoteproc core has supported only 32-bit remote
> processors and as such some of the current resource structures
> may not scale well for 64-bit remote processors, and would
> require new versions of resource types. Each resource is currently
> identified by a 32-bit type field. Introduce the concept of version
> for these resource types by overloading this 32-bit type field
> into two 16-bit version and type fields with the existing resources
> behaving as version 0 thereby providing backward compatibility.
> 
> The version field is passed as an additional argument to each of
> the handler functions, and all the existing handlers are updated
> accordingly. Each specific handler will be updated on a need basis
> when a new version of the resource type is added.
> 

I really would prefer that we add additional types for the new
structures, neither side will be compatible with new versions without
enhancements to their respective implementations anyways.

> An alternate way would be to introduce the new types as completely
> new resource types which would require additional customization of
> the resource handlers based on the 32-bit or 64-bit mode of a remote
> processor, and introduction of an additional mode flag to the rproc
> structure.
> 

What would this "mode" indicate? If it's version 0 or 1?

> Signed-off-by: Suman Anna <s-anna@...com>
> ---
>  drivers/remoteproc/remoteproc_core.c    | 25 +++++++++++++++----------
>  drivers/remoteproc/remoteproc_debugfs.c | 17 ++++++++++-------
>  include/linux/remoteproc.h              |  8 +++++++-
>  3 files changed, 32 insertions(+), 18 deletions(-)
> 
[..]
> diff --git a/include/linux/remoteproc.h b/include/linux/remoteproc.h
> index 77788a4bb94e..526d3cb45e37 100644
> --- a/include/linux/remoteproc.h
> +++ b/include/linux/remoteproc.h
> @@ -86,7 +86,13 @@ struct resource_table {
>   * this header, and it should be parsed according to the resource type.
>   */
>  struct fw_rsc_hdr {
> -	u32 type;
> +	union {
> +		u32 type;
> +		struct {
> +			u16 t;
> +			u16 v;
> +		} st;

I see your "type" is little endian...

Regards,
Bjorn