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

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Date:   Fri, 6 Mar 2020 15:55:46 -0800
From:   Jolly Shah <jolly.shah@...inx.com>
To:     "'Greg KH'" <gregkh@...uxfoundation.org>,
        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

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.

Thanks,
Jolly Shah

> 
> thanks,
> 
> greg k-h
>