linux-kernel - Re: [PATCH v2 07/19] remoteproc: Add new resource type for resource table spare bytes

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Date:   Fri, 16 Sep 2016 10:12:38 -0700
From:   Bjorn Andersson <bjorn.andersson@...aro.org>
To:     loic pallardy <loic.pallardy@...com>
Cc:     ohad@...ery.com, lee.jones@...aro.org,
        linux-remoteproc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...inux.com
Subject: Re: [PATCH v2 07/19] remoteproc: Add new resource type for resource
 table spare bytes

On Fri 16 Sep 02:02 PDT 2016, loic pallardy wrote:

> 
> 
> On 09/15/2016 07:54 PM, Bjorn Andersson wrote:
> >On Wed 31 Aug 13:50 PDT 2016, Loic Pallardy wrote:
> >
> >>To allow resource appending to an existing resource table,
> >>remoteproc framework should get information about resource
> >>table spare area. With current resource table construction,
> >>remoteproc is not able to identify by itself any free location.
> >>This patch introduces a new resource type named RSC_SPARE which
> >>allows firmware to define room for resource table extension.
> >>Defined spare area will be used by remtoreproc to extend resource
> >>table.
> >>
> >
> >We don't need a dummy type for keeping track of the available room in
> >the resource table in the loaded firmware. All we need to do is to look
> >at the sh_size of the .resource_table section, which actually is what's
> >returned in tablesz.
> >
> This is the size of the .resource_table section. Doesn't means that only
> resource table is stored in.

I'm not sure I'm getting the details of what you're saying here. Do you
mean that there could be other things in the resource_table section or
just the fact that it being a section doesn't give any information about
how much space this thing will have in loaded form.

> Today this is the assumption and we force firmware to respect this.
> 

I find it unfortunate that this was put in section and that we just have
to make assumptions on how this projects onto the loaded form.

> >So the spare size is the difference between tablesz and the end of the
> >last resource and if you need you can pad this when composing the
> >firmware.
> >
> Proposal was to clearly identify the area for extension (whatever
> .resource_table section is done). But if you agree on the fact
> .resource_tabel section constains only resource table and eventualy room for
> extension, I can indeed simply room detection.
> 

Could you describe your use case for programmatically generate a
resource table for a firmware without a .resource_table? I would like to
understand the contract between the driver and the firmware when it
comes to what should go into the resource table.

Regards,
Bjorn