linux-kernel - Re: [Outreachy kernel] Re: [PATCH v2 4/6] staging: fbtft: Fix sparse warnings of incorrect type in assignment

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Date:   Sat, 4 Mar 2017 16:06:34 -0800
From:   Alison Schofield <amsfield22@...il.com>
To:     singhalsimran0@...il.com,
        Noralf Trønnes <noralf@...nnes.org>
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,
        outreachy-kernel@...glegroups.com
Subject: Re: [Outreachy kernel] Re: [PATCH v2 4/6] staging: fbtft: Fix sparse
 warnings of incorrect type in assignment

On Thu, Mar 02, 2017 at 02:26:37PM +0100, Noralf Trønnes wrote:
> 
> Den 02.03.2017 14.04, skrev simran singhal:
> >This patch fixes the following sparse warnings:
> >
> >drivers/staging/fbtft/fbtft-bus.c:166:36: warning: incorrect type in assignment (different base types)
> >drivers/staging/fbtft/fbtft-bus.c:166:36:    expected unsigned short [unsigned] [short] [usertype] <noident>
> >drivers/staging/fbtft/fbtft-bus.c:166:36:    got restricted __be16 [usertype] <noident>
> >
> >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>
> >---
> >  v2:
> >    -changed commit message
> >
> >  drivers/staging/fbtft/fbtft-bus.c | 2 +-
> >  drivers/staging/fbtft/fbtft-io.c  | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> >
> >diff --git a/drivers/staging/fbtft/fbtft-bus.c b/drivers/staging/fbtft/fbtft-bus.c
> >index ec45043..df2223e 100644
> >--- a/drivers/staging/fbtft/fbtft-bus.c
> >+++ b/drivers/staging/fbtft/fbtft-bus.c
> >@@ -163,7 +163,7 @@ int fbtft_write_vmem16_bus8(struct fbtft_par *par, size_t offset, size_t len)
> >  						to_copy, remain - to_copy);
> >  		for (i = 0; i < to_copy; i++)
> >-			txbuf16[i] = cpu_to_be16(vmem16[i]);
> >+			txbuf16[i] = vmem16[i];
> 
> This change breaks functionality on little endian machines like
> the Raspberry Pi.
> 
> 
> Noralf.
> 

Hi Simran,

It's probably good to get back to this one while we have Noralf's
attention.

While the change above - in fbtft-bus.c is a problem, the change
below in fbtft-io.c looks ok.  So, compare what you did.  You can't
*not* do the endian conversion.

This is a cleanup change, a cosmetic change.  There is no underlying
bug, so you just need to get the typing correct w/out affecting
behavior.

BTW: I think it's OK to pull this one out and send a v3 of this alone.
That would mean abandoning the patchset and doing them one at a time.
They are all in different drivers anyway.

alisons



> >  		vmem16 = vmem16 + to_copy;
> >  		ret = par->fbtftops.write(par, par->txbuf.buf,
> >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++;
> 
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