linux-kernel - Re: [Outreachy kernel] [PATCH v3 4/6] staging: fbtft: Fix sparse warnings of incorrect type in assignment

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Message-ID: <20170305053624.GA8079@d830.WORKGROUP>
Date:   Sat, 4 Mar 2017 21:36:25 -0800
From:   Alison Schofield <amsfield22@...il.com>
To:     simran singhal <singhalsimran0@...il.com>
Cc:     gregkh@...uxfoundation.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, sergio.paracuellos@...il.com,
        juliana.orod@...il.com, thomas.petazzoni@...e-electrons.com,
        noralf@...nnes.org, outreachy-kernel@...glegroups.com
Subject: Re: [Outreachy kernel] [PATCH v3 4/6] staging: fbtft: Fix sparse
 warnings of incorrect type in assignment

On Sun, Mar 05, 2017 at 10:35:33AM +0530, simran singhal wrote:
> This patch fixes the following sparse warnings:
> 
> drivers/staging/fbtft/fbtft-io.c:74:29: warning: incorrect type in assignment (different base types)
> drivers/staging/fbtft/fbtft-io.c:74:29:    expected unsigned long long [unsigned] [long] [long long] [usertype] <noident>
> drivers/staging/fbtft/fbtft-io.c:74:29:    got restricted __be64 [usertype] <noident>
> 
> Signed-off-by: simran singhal <singhalsimran0@...il.com>
> ---
>  
>  v3:
>    -Change commit message
>    -Drop the changes did in fbtft-bus.c

Hi Simran, 

Sorry, I didn't mean to drop the broken part of fbtft, but rather to fix it.

Let's tidy up a few things:
- we can't send out one patch labelled as part of a patchset without
  resending the entire set.  That's why I was suggesting just abandoning
  the patchset, and beginning to rework this anew with only the fbtft
  driver in a single patch.
- I suggest keeping the -bus and -io file changes together.
- Look to correct what is wrong with fbtft-bus.c before sending a new
  patch.
- Patch Subject would be something like: use __be64 types for endian
  correctness (if this is what you end up doing - hint)

So, next step,
1) read up on endianess and propose how to change -bus.c.
   OK to check that idea/code snippet here without re-rolling the patch.

   https://kernelnewbies.org/EndianIssues
   and Vaishali also gave a good link to lwn.net article
   and to see some example fixes (in iio subsystem) do this:
	git log --pretty=oneline --abbrev-commit | grep iio | grep endian


2) build the patch.  At this point I say make it a first version and
   start totally fresh.  However, below the line --- where you usually
   put the version comments, you can add a comment stating that this
   was previously part of a patchset, but is now a single patch.
  
alisons


>   
>  drivers/staging/fbtft/fbtft-io.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/staging/fbtft/fbtft-io.c b/drivers/staging/fbtft/fbtft-io.c
> index d868405..ffb9a3b 100644
> --- a/drivers/staging/fbtft/fbtft-io.c
> +++ b/drivers/staging/fbtft/fbtft-io.c
> @@ -71,7 +71,7 @@ int fbtft_write_spi_emulate_9(struct fbtft_par *par, void *buf, size_t len)
>  			src++;
>  		}
>  		tmp |= ((*src & 0x0100) ? 1 : 0);
> -		*(u64 *)dst = cpu_to_be64(tmp);
> +		*(__be64 *)dst = cpu_to_be64(tmp);
>  		dst += 8;
>  		*dst++ = (u8)(*src++ & 0x00FF);
>  		added++;
> -- 
> 2.7.4
> 
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