linux-kernel - Re: [PATCH v9 1/5] firmware: add extensible driver data params

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Date:   Tue, 20 Jun 2017 10:48:14 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     "Li, Yi" <yi1.li@...ux.intel.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>, wagi@...om.org,
        dwmw2@...radead.org, rafal@...ecki.pl,
        arend.vanspriel@...adcom.com, rjw@...ysocki.net,
        atull@...nsource.altera.com, moritz.fischer@...us.com,
        pmladek@...e.com, johannes.berg@...el.com,
        emmanuel.grumbach@...el.com, luciano.coelho@...el.com,
        kvalo@...eaurora.org, luto@...nel.org,
        torvalds@...ux-foundation.org, keescook@...omium.org,
        dhowells@...hat.com, pjones@...hat.com, hdegoede@...hat.com,
        alan@...ux.intel.com, tytso@....edu, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v9 1/5] firmware: add extensible driver data params

On Mon, Jun 19, 2017 at 05:51:08PM -0500, Li, Yi wrote:
> Hi Greg,
> 
> On 6/17/2017 2:38 PM, Greg KH wrote:
> >On Tue, Jun 13, 2017 at 09:40:11PM +0200, Luis R. Rodriguez wrote:
> >>On Tue, Jun 13, 2017 at 11:05:48AM +0200, Greg KH wrote:
> >>>On Mon, Jun 05, 2017 at 02:39:33PM -0700, Luis R. Rodriguez wrote:
> >
> >>What you have to ask yourself really is if this makes it *less complex* and
> >>helps *clean things up* in a much better way than it was before. Also does it
> >>allow us to *pave the way for new functionality easily*, without creating
> >>further mess?
> >
> >I agree, that's what I'm saying here.  I just do not see that happening
> >with your patch set at all.  It's adding more code, a more complex way
> >to interact with the subsystem, and not making driver writer lives any
> >easier at all that I can see.
> >
> >Again, the code is now bigger, does more, with not even any real benefit
> >for existing users.
> 
> I am still new to the upstreaming world, pardon me if my understanding is
> naive. :) My take with Luis's driver data API is that it adds a wrapper on
> top of the old request_firmware APIs, so the new features can be
> added/disabled by the parameters structures instead of adding/changing API
> functions. Agree that there is not much new for existing users. It adds more
> codes (not necessary more complex) but create a consistent way for extension
> IMO.

Most of code of my feature, firmware signing, is implemented in common
place between old and new APIs, while only new API has a parameter,
DRIVER_DATA_REQ_NO_SIG_CHECK, which allow users to enable/disable
this feature per-driver-datum. Simple enough.

So what matters is adding yet another variant of request_firmware_xx()
vs. adding a mere parameter?

Thanks,
-Takahiro AKASHI

> Below are 3 examples I tried to add streaming support to load large firmware
> files.
> Adding streaming with driver data API:
> https://patchwork.kernel.org/patch/9738503 . This patch series depends on
> non-cache patch series https://patchwork.kernel.org/patch/9793825 , which is
> bigger than it should be since it added some codes to test firmware caching.
> and pre-allocate buffer patch series
> https://patchwork.kernel.org/patch/9738487/
> 
> By comparison, here is my old streaming RFC with original firmware class:
> https://lkml.org/lkml/2017/3/9/872
> Do you think this is the better way?
> 
> Thanks,
> Yi