netdev - Re: [PATCH v5 net-next 5/5] net: wwan: t7xx: Devlink documentation

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Message-ID: <20230125100812.026c0a1e@kernel.org>
Date:   Wed, 25 Jan 2023 10:08:12 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     "Kumar, M Chetan" <m.chetan.kumar@...ux.intel.com>
Cc:     netdev@...r.kernel.org, davem@...emloft.net,
        johannes@...solutions.net, ryazanov.s.a@...il.com,
        loic.poulain@...aro.org, ilpo.jarvinen@...ux.intel.com,
        ricardo.martinez@...ux.intel.com,
        chiranjeevi.rapolu@...ux.intel.com, haijun.liu@...iatek.com,
        edumazet@...gle.com, pabeni@...hat.com,
        chandrashekar.devegowda@...el.com, linuxwwan@...el.com,
        linuxwwan_5g@...el.com, corbet@....net, linux-doc@...r.kernel.org,
        jiri@...dia.com
Subject: Re: [PATCH v5 net-next 5/5] net: wwan: t7xx: Devlink documentation

On Wed, 25 Jan 2023 16:03:37 +0530 Kumar, M Chetan wrote:
> > I don't know what fastboot is, and reading this doc I see it used in
> > three forms:
> >   - fastboot protocol
> >   - fastboot mode
> >   - fastboot command & response  
> 
> The fastboot is sort of a tool. It implements the protocol for 
> programming the device flash or getting device information. The device 
> implements the fastboot commands and host issue those commands for 
> programming the firmware to device flash or to obtain device 
> information. Inorder to execute those commands, first the device needs 
> to be put into fastboot mode.
> 
> More details on fastboot can be found in links [1].
> 
> > In the end - I have no idea what the devlink param you're adding does.  
> 
> "fastboot" devlink param is used to put the device into fastboot mode
> to program firmware to device flash or to obtain device information.
> 
> 
> [1]
> https://en.wikipedia.org/wiki/Fastboot
> https://android.googlesource.com/platform/system/core/+/refs/heads/master/fastboot/README.md

As Ilpo mentions, please add this info into the doc, including 
the links.

The most confusing part is that "fastboot" sounds like it's going 
to boot fast, while IIUC the behavior is the opposite - it's not going
to boot at all and just expose an interface to load the FW, is that
right?

Please also clarify what the normal operation for the device is.
In what scenarios does the fastboot mode get used?

And just to double confirm - that the FW loaded in fastboot mode is
persistently stored on the device, and will be used after power cycle.
Rather than it being an upload into RAM.