linux-kernel - Re: [PATCH v2 1/4] firmware: xilinx: Add sysfs interface

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Message-ID: <20200307084711.GA3877697@kroah.com>
Date:   Sat, 7 Mar 2020 09:47:11 +0100
From:   'Greg KH' <gregkh@...uxfoundation.org>
To:     Jolly Shah <jolly.shah@...inx.com>
Cc:     Rajan Vaja <RAJANV@...inx.com>,
        "ard.biesheuvel@...aro.org" <ard.biesheuvel@...aro.org>,
        "mingo@...nel.org" <mingo@...nel.org>,
        "matt@...eblueprint.co.uk" <matt@...eblueprint.co.uk>,
        "sudeep.holla@....com" <sudeep.holla@....com>,
        "hkallweit1@...il.com" <hkallweit1@...il.com>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
        Michal Simek <michals@...inx.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/4] firmware: xilinx: Add sysfs interface

On Fri, Mar 06, 2020 at 03:55:46PM -0800, Jolly Shah wrote:
> Hi Greg,
> 
> > ------Original Message------
> > From: 'Greg Kh' <gregkh@...uxfoundation.org>
> > Sent:  Friday, February 14, 2020 4:52PM
> > To: Jolly Shah <jolly.shah@...inx.com>
> > Cc: Rajan Vaja <RAJANV@...inx.com>, Ard.biesheuvel@...aro.org
> <ard.biesheuvel@...aro.org>, Mingo@...nel.org <mingo@...nel.org>,
> Matt@...eblueprint.co.uk <matt@...eblueprint.co.uk>, Sudeep.holla@....com
> <sudeep.holla@....com>, Hkallweit1@...il.com <hkallweit1@...il.com>,
> Keescook@...omium.org <keescook@...omium.org>, Dmitry.torokhov@...il.com
> <dmitry.torokhov@...il.com>, Michal Simek <michals@...inx.com>,
> Linux-arm-kernel@...ts.infradead.org <linux-arm-kernel@...ts.infradead.org>,
> Linux-kernel@...r.kernel.org <linux-kernel@...r.kernel.org>
> > Subject: Re: [PATCH v2 1/4] firmware: xilinx: Add sysfs interface
> >
> > On Fri, Feb 14, 2020 at 04:37:16PM -0800, Jolly Shah wrote:
> > > > Just make the direct call to the firmware driver, no need to muck around
> > > > with tables of function pointers.  In fact, with the spectre changes,
> > > > you just made things slower than needed, and you can get back a bunch of
> > > > throughput by removing that whole middle layer.
> > > > 
> > > 
> > > arm,scpi is doing the same way and we thought this approach will be more
> > > acceptable than direct function calls but happy to change as suggested.
> > 
> > Just because one random tiny thing does it the wrong way does not mean
> > to focus on that design pattern and ignore the thousands of other
> > apis/interfaces in the kernel that do not do it that way :)
> > 
> > > > So go do that first please, before adding any new stuff.
> > > > 
> > > > Now for the ioctl, yeah, that's not a "normal" pattern either.  But
> > > > right now you only have 2 "different" ioctls that you call.  So why not
> > > > just turn those 2 into real function calls as well that then makes the
> > > > "ioctl" call to the hardware?  That makes things a lot more obvious on
> > > > the kernel driver side exactly what is going on.
> > > > 
> > > 
> > > Sure as i understand firmware driver will provide real function calls to be
> > > used by user drivers and underneath it will call ioctl for desired
> > > operation. Please correct if I misunderstood.
> > 
> > You do not misunderstand.
> 
> Submitted v3 with required changes. Please review.

Will do, when I get to it, relax :)