[patch 15/17] drivers/scsi: Use DIV_ROUND_UP

[patch 15/17] drivers/scsi: Use DIV_ROUND_UP

[akpm]

From: Julia Lawall <julia@diku.dk>

The kernel.h macro DIV_ROUND_UP performs the computation (((n) + (d) - 1) /
(d)) but is perhaps more readable.

An extract of the semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@haskernel@
@@

#include <linux/kernel.h>

@depends on haskernel@
expression n,d;
@@

(
- (n + d - 1) / d
+ DIV_ROUND_UP(n,d)
|
- (n + (d - 1)) / d
+ DIV_ROUND_UP(n,d)
)

@depends on haskernel@
expression n,d;
@@

- DIV_ROUND_UP((n),d)
+ DIV_ROUND_UP(n,d)

@depends on haskernel@
expression n,d;
@@

- DIV_ROUND_UP(n,(d))
+ DIV_ROUND_UP(n,d)
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 drivers/scsi/esp_scsi.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff -puN drivers/scsi/esp_scsi.c~drivers-scsi-use-div_round_up drivers/scsi/esp_scsi.c
--- a/drivers/scsi/esp_scsi.c~drivers-scsi-use-div_round_up
+++ a/drivers/scsi/esp_scsi.c
@@ -1464,7 +1464,7 @@ static void esp_msgin_sdtr(struct esp *e
 
 		one_clock = esp->ccycle / 1000;
 		rounded_up = (period << 2);
-		rounded_up = (rounded_up + one_clock - 1) / one_clock;
+		rounded_up = DIV_ROUND_UP(rounded_up, one_clock);
 		stp = rounded_up;
 		if (stp && esp->rev >= FAS236) {
 			if (stp >= 50)
_

Re: [patch 15/17] drivers/scsi: Use DIV_ROUND_UP

[Matthew Wilcox]

On Mon, Sep 22, 2008 at 02:56:51PM -0700, akpm@linux-foundation.org wrote:
>  
>  		one_clock = esp->ccycle / 1000;
>  		rounded_up = (period << 2);
> -		rounded_up = (rounded_up + one_clock - 1) / one_clock;
> +		rounded_up = DIV_ROUND_UP(rounded_up, one_clock);
>  		stp = rounded_up;
>  		if (stp && esp->rev >= FAS236) {
>  			if (stp >= 50)

Is this not exactly equivalent to:

		one_clock = esp->ccycle / 1000;
		stp = DIV_ROUND_UP(period << 2, one_clock);

(rounded_up is local to this if condition).

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

Re: [patch 15/17] drivers/scsi: Use DIV_ROUND_UP

[Julia Lawall]

On Mon, 22 Sep 2008, Matthew Wilcox wrote:

> On Mon, Sep 22, 2008 at 02:56:51PM -0700, akpm@linux-foundation.org wrote:
> >  
> >  		one_clock = esp->ccycle / 1000;
> >  		rounded_up = (period << 2);
> > -		rounded_up = (rounded_up + one_clock - 1) / one_clock;
> > +		rounded_up = DIV_ROUND_UP(rounded_up, one_clock);
> >  		stp = rounded_up;
> >  		if (stp && esp->rev >= FAS236) {
> >  			if (stp >= 50)
> 
> Is this not exactly equivalent to:
> 
> 		one_clock = esp->ccycle / 1000;
> 		stp = DIV_ROUND_UP(period << 2, one_clock);
> 
> (rounded_up is local to this if condition).

Agreed.  An updated patch is below.

julia

--------------------

From: Julia Lawall <julia@diku.dk>

Use the macro DIV_ROUND_UP and eliminate the variable rounded_up, as
suggested by Matthew Wilcox.

Signed-off-by: Julia Lawall <julia@diku.dk>

---

 drivers/scsi/esp_scsi.c       |    6 ++----
 1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
index 62a4618..a680e18 100644
--- a/drivers/scsi/esp_scsi.c
+++ b/drivers/scsi/esp_scsi.c
@@ -1453,7 +1453,7 @@ static void esp_msgin_sdtr(struct esp *esp, struct esp_target_data *tp)
 		offset = 0;
 
 	if (offset) {
-		int rounded_up, one_clock;
+		int one_clock;
 
 		if (period > esp->max_period) {
 			period = offset = 0;
@@ -1463,9 +1463,7 @@ static void esp_msgin_sdtr(struct esp *esp, struct esp_target_data *tp)
 			goto do_reject;
 
 		one_clock = esp->ccycle / 1000;
-		rounded_up = (period << 2);
-		rounded_up = (rounded_up + one_clock - 1) / one_clock;
-		stp = rounded_up;
+		stp = DIV_ROUND_UP(period << 2, one_clock);
 		if (stp && esp->rev >= FAS236) {
 			if (stp >= 50)
 				stp--;

Re: [patch 15/17] drivers/scsi: Use DIV_ROUND_UP

[Matthew Wilcox]

On Wed, Sep 24, 2008 at 09:26:48PM +0200, Julia Lawall wrote:
> --------------------
> 
> From: Julia Lawall <julia@diku.dk>
> 
> Use the macro DIV_ROUND_UP and eliminate the variable rounded_up, as
> suggested by Matthew Wilcox.
> 
> Signed-off-by: Julia Lawall <julia@diku.dk>

Reviewed-by: Matthew Wilcox <willy@linux.intel.com>

> ---
> 
>  drivers/scsi/esp_scsi.c       |    6 ++----
>  1 files changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c
> index 62a4618..a680e18 100644
> --- a/drivers/scsi/esp_scsi.c
> +++ b/drivers/scsi/esp_scsi.c
> @@ -1453,7 +1453,7 @@ static void esp_msgin_sdtr(struct esp *esp, struct esp_target_data *tp)
>  		offset = 0;
>  
>  	if (offset) {
> -		int rounded_up, one_clock;
> +		int one_clock;
>  
>  		if (period > esp->max_period) {
>  			period = offset = 0;
> @@ -1463,9 +1463,7 @@ static void esp_msgin_sdtr(struct esp *esp, struct esp_target_data *tp)
>  			goto do_reject;
>  
>  		one_clock = esp->ccycle / 1000;
> -		rounded_up = (period << 2);
> -		rounded_up = (rounded_up + one_clock - 1) / one_clock;
> -		stp = rounded_up;
> +		stp = DIV_ROUND_UP(period << 2, one_clock);
>  		if (stp && esp->rev >= FAS236) {
>  			if (stp >= 50)
>  				stp--;
> --
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-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."