[PATCH] spi: atmel: Fix test unsigned var < 0

[PATCH] spi: atmel: Fix test unsigned var < 0

[Axel Lin]

current_remaining_bytes is an unsigned long and cannot be below 0.

Signed-off-by: Axel Lin <axel.lin-8E1dMatC8ynQT0dZR+AlfA@public.gmane.org>
---
 drivers/spi/spi-atmel.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index bda961e..3e8c4cc 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -873,13 +873,11 @@ atmel_spi_pump_pio_data(struct atmel_spi *as, struct spi_transfer *xfer)
 	} else {
 		spi_readl(as, RDR);
 	}
-	if (xfer->bits_per_word > 8) {
+
+	if (xfer->bits_per_word > 8)
 		as->current_remaining_bytes -= 2;
-		if (as->current_remaining_bytes < 0)
-			as->current_remaining_bytes = 0;
-	} else {
+	else
 		as->current_remaining_bytes--;
-	}
 }
 
 /* Interrupt
-- 
1.8.3.2



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Re: [PATCH] spi: atmel: Fix test unsigned var < 0

[Mark Brown]

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On Sat, Mar 22, 2014 at 10:33:29PM +0800, Axel Lin wrote:
> current_remaining_bytes is an unsigned long and cannot be below 0.

> -	if (xfer->bits_per_word > 8) {
> +
> +	if (xfer->bits_per_word > 8)
>  		as->current_remaining_bytes -= 2;
> -		if (as->current_remaining_bytes < 0)
> -			as->current_remaining_bytes = 0;
> -	} else {
> +	else
>  		as->current_remaining_bytes--;
> -	}

This removes an error check in the case that we set the remaining bytes
to -1.  The length validation the core does should ensure that never
happens but it seems wrong to just ignore that - we should at least note
in the changelog that the analysis has been done.

Are you sure that the best fix isn't to just use an int here?

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Re: [PATCH] spi: atmel: Fix test unsigned var < 0

[Axel Lin]

2014-03-27 0:51 GMT+08:00 Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>:
> On Sat, Mar 22, 2014 at 10:33:29PM +0800, Axel Lin wrote:
>> current_remaining_bytes is an unsigned long and cannot be below 0.
>
>> -     if (xfer->bits_per_word > 8) {
>> +
>> +     if (xfer->bits_per_word > 8)
>>               as->current_remaining_bytes -= 2;
>> -             if (as->current_remaining_bytes < 0)
>> -                     as->current_remaining_bytes = 0;
>> -     } else {
>> +     else
>>               as->current_remaining_bytes--;
>> -     }
>
> This removes an error check in the case that we set the remaining bytes
> to -1.  The length validation the core does should ensure that never
> happens but it seems wrong to just ignore that - we should at least note
> in the changelog that the analysis has been done.
I thought it never happen and there is no bug report for this so it's
safe with this patch.

>
> Are you sure that the best fix isn't to just use an int here?
Wenyou,
  Any comments for this?

Regards,
Axel
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RE: [PATCH] spi: atmel: Fix test unsigned var < 0

[Yang, Wenyou]

> -----Original Message-----
> From: Axel Lin [mailto:axel.lin-8E1dMatC8ynQT0dZR+AlfA@public.gmane.org]
> Sent: Thursday, March 27, 2014 8:46 AM
> To: Mark Brown
> Cc: Yang, Wenyou; linux-spi
> Subject: Re: [PATCH] spi: atmel: Fix test unsigned var < 0
> 
> 2014-03-27 0:51 GMT+08:00 Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>:
> > On Sat, Mar 22, 2014 at 10:33:29PM +0800, Axel Lin wrote:
> >> current_remaining_bytes is an unsigned long and cannot be below 0.
> >
> >> -     if (xfer->bits_per_word > 8) {
> >> +
> >> +     if (xfer->bits_per_word > 8)
> >>               as->current_remaining_bytes -= 2;
> >> -             if (as->current_remaining_bytes < 0)
> >> -                     as->current_remaining_bytes = 0;
> >> -     } else {
> >> +     else
> >>               as->current_remaining_bytes--;
> >> -     }
> >
> > This removes an error check in the case that we set the remaining
> > bytes to -1.  The length validation the core does should ensure that
> > never happens but it seems wrong to just ignore that - we should at
> > least note in the changelog that the analysis has been done.
> I thought it never happen and there is no bug report for this so it's
> safe with this patch.
> 
> >
> > Are you sure that the best fix isn't to just use an int here?
> Wenyou,
>   Any comments for this?

Like Mark said, It seems it is more reasonable using a signed int, instead of unsigned int.

-->8 ---
diff --git a/drivers/spi/spi-atmel.c b/drivers/spi/spi-atmel.c
index 8005f98..485e6cc 100644
--- a/drivers/spi/spi-atmel.c
+++ b/drivers/spi/spi-atmel.c
@@ -224,7 +224,7 @@ struct atmel_spi {
 	struct platform_device	*pdev;
 
 	struct spi_transfer	*current_transfer;
-	unsigned long		current_remaining_bytes;
+	int			current_remaining_bytes;
 	int			done_status;
 
 	struct completion	xfer_completion;
@@ -1110,6 +1110,8 @@ static int atmel_spi_one_transfer(struct spi_master *master,
 				atmel_spi_next_xfer_pio(master, xfer);
 			} else {
 				as->current_remaining_bytes -= len;
+				if (as->current_remaining_bytes < 0)
+					as->current_remaining_bytes = 0;
 			}
 		} else {
 			atmel_spi_next_xfer_pio(master, xfer);
--<8 ---

Best Regards,
Wenyou Yang
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Re: [PATCH] spi: atmel: Fix test unsigned var < 0

[Axel Lin]

2014-03-27 9:13 GMT+08:00 Yang, Wenyou <Wenyou.Yang-AIFe0yeh4nAAvxtiuMwx3w@public.gmane.org>:
>
>> -----Original Message-----
>> From: Axel Lin [mailto:axel.lin-8E1dMatC8ynQT0dZR+AlfA@public.gmane.org]
>> Sent: Thursday, March 27, 2014 8:46 AM
>> To: Mark Brown
>> Cc: Yang, Wenyou; linux-spi
>> Subject: Re: [PATCH] spi: atmel: Fix test unsigned var < 0
>>
>> 2014-03-27 0:51 GMT+08:00 Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>:
>> > On Sat, Mar 22, 2014 at 10:33:29PM +0800, Axel Lin wrote:
>> >> current_remaining_bytes is an unsigned long and cannot be below 0.
>> >
>> >> -     if (xfer->bits_per_word > 8) {
>> >> +
>> >> +     if (xfer->bits_per_word > 8)
>> >>               as->current_remaining_bytes -= 2;
>> >> -             if (as->current_remaining_bytes < 0)
>> >> -                     as->current_remaining_bytes = 0;
>> >> -     } else {
>> >> +     else
>> >>               as->current_remaining_bytes--;
>> >> -     }
>> >
>> > This removes an error check in the case that we set the remaining
>> > bytes to -1.  The length validation the core does should ensure that
>> > never happens but it seems wrong to just ignore that - we should at
>> > least note in the changelog that the analysis has been done.
>> I thought it never happen and there is no bug report for this so it's
>> safe with this patch.
>>
>> >
>> > Are you sure that the best fix isn't to just use an int here?
>> Wenyou,
>>   Any comments for this?
>
> Like Mark said, It seems it is more reasonable using a signed int, instead of unsigned int.
OK. I'm sending a formal patch with your Signed-off-by now.

Regards,
Axel
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