linux-kernel - Re: [PATCH] staging: vc04_services: tie up loose ends with dma_map

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Message-ID: <1477668994.12378.1.camel@crowfest.net>
Date:   Fri, 28 Oct 2016 08:36:34 -0700
From:   Michael Zoran <mzoran@...wfest.net>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     eric@...olt.net, swarren@...dotorg.org, lee@...nel.org,
        daniels@...labora.com, noralf@...nnes.org, popcornmix@...il.com,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: vc04_services: tie up loose ends with
 dma_map_sg conversion

On Fri, 2016-10-28 at 11:31 -0400, Greg KH wrote:
> On Fri, Oct 28, 2016 at 08:16:51AM -0700, Michael Zoran wrote:
> > The conversion to dma_map_sg left a few loose ends.  This change
> > ties up those loose ends.
> > 
> > 1. Settings the DMA mask is mandatory on 64 bit even though it
> > is optional on 32 bit.  Set the mask so that DMA space is always
> > in the lower 32 bit range of data on both platforms.
> > 
> > 2. The scatterlist was not completely initialized correctly.
> > Initialize the list with sg_init_table so that DMA works correctly
> > if scatterlist debugging is enabled in the build configuration.
> > 
> > 3. The error paths in create_pagelist were not consistent.  Make
> > them all consistent by calling a helper function called
> > cleanup_pagelistinfo to cleanup regardless of what state the
> > pagelist
> > is in.
> > 
> > 4. create_pagelist and free_pagelist had a very large amount of
> > duplication in computing offsets into a single allocation of memory
> > in the DMA area.  Introduce a new structure called the pagelistinfo
> > that is appened to the end of the allocation to store necessary
> > information to prevent duplication of code and make cleanup on
> > errors
> > easier.
> > 
> > When combined with a fix for vchiq_copy_from_user which is not
> > included at this time, both functional and pings tests of
> > vchiq_test
> > now pass in both 32 bit and 64 bit modes.
> > 
> > Even though this cleanup could have been broken down to chunks,
> > all the changes are to a single file and submitting it as a single
> > related change should make reviewing the diff much easier then if
> > it
> > were submitted piecemeal.
> 
> No, it's harder.  A patch should only do one type of thing, this
> patch
> has to be reviewed thinking of 4 different things all at once, making
> it
> much more difficult to do so.
> 
> We write patches to be read easily, and make them easy to review.  We
> don't write them in a way to be easy for the developer to create :)
> 
> Can you please break this up into a patch series?
> 
> thanks,
> 
> greg k-h

Point #1 and #2 would be very easy to seperate.   Point #3 and #4 are
essentually a redo of two major functions and are where most of the
changes are.

Would making #1 and #2 independent but combining #3 and #4 sufficient?