linux-kernel - Re: [PATCH v2 4/5] firmware: generalize reading file contents as a helper

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Message-ID: <20151008225437.GL14464@wotan.suse.de>
Date:	Fri, 9 Oct 2015 00:54:37 +0200
From:	"Luis R. Rodriguez" <mcgrof@...e.com>
To:	Josh Boyer <jwboyer@...oraproject.org>
Cc:	"Luis R. Rodriguez" <mcgrof@...not-panic.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	Ming Lei <ming.lei@...onical.com>,
	Jonathan Corbet <corbet@....net>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	linux-doc@...r.kernel.org, David Woodhouse <dwmw2@...radead.org>,
	David Howells <dhowells@...hat.com>,
	Seth Forshee <seth.forshee@...onical.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Michal Marek <mmarek@...e.cz>,
	Matthew Garrett <mjg59@...f.ucam.org>, kyle@...nel.org,
	linux-security-module <linux-security-module@...r.kernel.org>,
	keyrings@...ux-nfs.org, Tom Gundersen <teg@...m.no>
Subject: Re: [PATCH v2 4/5] firmware: generalize reading file contents as a
 helper

On Thu, Oct 08, 2015 at 01:36:53PM -0400, Josh Boyer wrote:
> On Thu, Oct 1, 2015 at 1:44 PM, Luis R. Rodriguez
> <mcgrof@...not-panic.com> wrote:
> > From: David Howells <dhowells@...hat.com>
> >
> > We'll want to reuse this same code later in order to
> > read two separate types of file contents. This generalizes
> > fw_read_file() for reading a file rebrands it as fw_read_file().
> 
> Er, maybe that should read "...fw_read_file_contents() for reading a
> file and rebrands it as fw_read_file()." ?

Thanks, corrected.

> > This caller lets us pegs arbitrary data onto the target
> > buffer and size if the file is found.
> 
> This sentence is somewhat confusing.  The data isn't arbitrary. It is
> what the caller wants you to read from path.  What is arbitrary, at
> least in the context of this function, is the path passed to it.
> Maybe rewrite this as:
> 
> "The new function allows us to read file contents from arbitrary paths
> and return the data and size of the files read."

The path is arbitrary but what I meant by arbitrary data is that
the data need no longer be firmware, whereas fw_read_file_contents()
*did* require passing firmware_class data structures. What this does
is it make the possibility of eventually making a more core system
data file reader more obvious, so for instance the goal is to later
share a reader with:

    - firmware_class: fw_read_file()
    - module: kernel_read()
    - kexec: copy_file_fd()

I will clarify this in the commit log and also clarify the path is
arbitrary as well as you note.

> > While at it this cleans up the exit paths on fw_read_file().
> >
> > Signed-off-by: David Howells <dhowells@...hat.com>
> > Signed-off-by: Luis R. Rodriguez <mcgrof@...e.com>
> 
> The code changes themselves look fine.

Thank you for the review. Can I peg your Acked-by or Reviewed-by?
How about this for a change in the commit log:

firmware: generalize reading file contents as a helper                          

We'll want to reuse this same code later in order to read                       
two separate types of file contents. This generalizes                            
fw_read_file_contents() for reading a file and rebrands it                      
as fw_read_file(). This new caller is now generic and that                      
path can be arbitrary, the caller is also agnostic to the                       
firmware_class code now, which begs the possibility of code                     
re-use with other similar callers in the kernel. For instance                   
in the future we may want to share a solution with:                             

    - firmware_class: fw_read_file()                                            
    - module: kernel_read()                                                     
    - kexec: copy_file_fd()                                                     

While at it this also cleans up the exit paths on fw_read_file().               

  Luis
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