linux-kernel - Re: [PATCH 5/5] nvmem: Add support for write-only instances

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Date:   Tue, 24 Mar 2020 15:59:58 +0000
From:   Nicholas Johnson <nicholas.johnson-opensource@...look.com.au>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] nvmem: Add support for write-only instances

On Tue, Mar 24, 2020 at 04:18:31PM +0100, Greg KH wrote:
> On Tue, Mar 24, 2020 at 02:24:21PM +0000, Nicholas Johnson wrote:
> > On Tue, Mar 24, 2020 at 01:25:46PM +0000, Srinivas Kandagatla wrote:
> > > 
> > > 
> > > On 24/03/2020 12:29, Greg KH wrote:
> > > > > But the Idea here is :
> > > > > We ended up with providing different options like read-only,root-only to
> > > > > nvmem providers combined with read/write callbacks.
> > > > > With that, there are some cases which are totally invalid, existing code
> > > > > does very minimal check to ensure that before populating with correct
> > > > > attributes to sysfs file. One of such case is with thunderbolt provider
> > > > > which supports only write callback.
> > > > > 
> > > > > With this new checks in place these flags and callbacks are correctly
> > > > > validated, would result in correct file attributes.
> > > > Why this crazy set of different groups?  You can set the mode of a sysfs
> > > > file in the callback for when the file is about to be created, that's so
> > > > much simpler and is what it is for.  This feels really hacky and almost
> > > > impossible to follow:(
> > > Thanks for the inputs, That definitely sounds much simpler to deal with.
> > > 
> > > Am guessing you are referring to is_bin_visible callback?
> > > 
> > > I will try to clean this up!
> > I am still onboard and willing do the work, but we may need to discuss
> > to be on the same page with new plans. How do you wish to do this?
> > 
> > Does this new approach still allow us to abort if we receive an invalid
> > configuration? Or do we still need to have something in nvmem_register()
> > to abort in invalid case?
> > 
> > The documentation of is_bin_visible says only read/write permissions are 
> > accepted. Does this mean that it will not take read-only or write-only? 
> > That is one way of interpreting it.
> 
> That's a funny way of interpreting it :)
Now that I look back, yes.

> 
> Please be sane, you pass back the permissions of the file, look at all
> of the places in the kernel is it used for examples...
It's more inexperience and sleep deprivation than insanity. I am working 
on those. :)

There is only one use of is_bin_visible but a lot for is_visible, so I 
will go off those.

Regards,
Nicholas

> 
> thanks,
> 
> greg k-h