[PATCH v2 2/7] staging: most: Using macro DIV_ROUND_UP

[PATCH v2 2/7] staging: most: Using macro DIV_ROUND_UP

[simran singhal]

The macro DIV_ROUND_UP performs the computation (((n) + (d) - 1) /(d)).
It clarifies the divisor calculations. This occurence was detected using
the coccinelle script:

@@
expression e1;
expression e2;
@@
(
- ((e1) + e2 - 1) / (e2)
+ DIV_ROUND_UP(e1,e2)
|
- ((e1) + (e2 - 1)) / (e2)
+ DIV_ROUND_UP(e1,e2)
)

Signed-off-by: simran singhal <singhalsimran0@gmail.com>
---
 
 v2:
   -Included kernel.h as DIV_ROUND_UP is defined in it,
    before it was giving compilation error.

 drivers/staging/most/hdm-dim2/dim2_hal.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/staging/most/hdm-dim2/dim2_hal.c b/drivers/staging/most/hdm-dim2/dim2_hal.c
index 0b9816c..d604ec09 100644
--- a/drivers/staging/most/hdm-dim2/dim2_hal.c
+++ b/drivers/staging/most/hdm-dim2/dim2_hal.c
@@ -18,6 +18,7 @@
 #include "dim2_errors.h"
 #include "dim2_reg.h"
 #include <linux/stddef.h>
+#include <linux/kernel.h>
 
 /*
  * Size factor for isochronous DBR buffer.
@@ -49,7 +50,7 @@
 #define DBR_SIZE  (16 * 1024) /* specified by IP */
 #define DBR_BLOCK_SIZE  (DBR_SIZE / 32 / DBR_MAP_SIZE)
 
-#define ROUND_UP_TO(x, d)  (((x) + (d) - 1) / (d) * (d))
+#define ROUND_UP_TO(x, d)  (DIV_ROUND_UP(x, (d)) * (d))
 
 /* -------------------------------------------------------------------------- */
 /* generic helper functions and macros */
@@ -117,7 +118,7 @@ static int alloc_dbr(u16 size)
 		return DBR_SIZE; /* out of memory */
 
 	for (i = 0; i < DBR_MAP_SIZE; i++) {
-		u32 const blocks = (size + DBR_BLOCK_SIZE - 1) / DBR_BLOCK_SIZE;
+		u32 const blocks = DIV_ROUND_UP(size, DBR_BLOCK_SIZE);
 		u32 mask = ~((~(u32)0) << blocks);
 
 		do {
@@ -137,7 +138,7 @@ static int alloc_dbr(u16 size)
 static void free_dbr(int offs, int size)
 {
 	int block_idx = offs / DBR_BLOCK_SIZE;
-	u32 const blocks = (size + DBR_BLOCK_SIZE - 1) / DBR_BLOCK_SIZE;
+	u32 const blocks = DIV_ROUND_UP(size, DBR_BLOCK_SIZE);
 	u32 mask = ~((~(u32)0) << blocks);
 
 	mask <<= block_idx % 32;
-- 
2.7.4

Re: [Outreachy kernel] [PATCH v2 2/7] staging: most: Using macro DIV_ROUND_UP

[Julia Lawall]

> @@ -117,7 +118,7 @@ static int alloc_dbr(u16 size)
>  		return DBR_SIZE; /* out of memory */
>
>  	for (i = 0; i < DBR_MAP_SIZE; i++) {
> -		u32 const blocks = (size + DBR_BLOCK_SIZE - 1) / DBR_BLOCK_SIZE;
> +		u32 const blocks = DIV_ROUND_UP(size, DBR_BLOCK_SIZE);
>  		u32 mask = ~((~(u32)0) << blocks);

Totally unrelated to DIV_ROUND_UP, would this code be a candidate for
GENMASK?

julia

>
>  		do {
> @@ -137,7 +138,7 @@ static int alloc_dbr(u16 size)
>  static void free_dbr(int offs, int size)
>  {
>  	int block_idx = offs / DBR_BLOCK_SIZE;
> -	u32 const blocks = (size + DBR_BLOCK_SIZE - 1) / DBR_BLOCK_SIZE;
> +	u32 const blocks = DIV_ROUND_UP(size, DBR_BLOCK_SIZE);
>  	u32 mask = ~((~(u32)0) << blocks);
>
>  	mask <<= block_idx % 32;
> --
> 2.7.4
>
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Re: [Outreachy kernel] [PATCH v2 2/7] staging: most: Using macro DIV_ROUND_UP

[Joe Perches]

On Wed, 2017-02-22 at 10:27 +0100, Julia Lawall wrote:
> > @@ -117,7 +118,7 @@ static int alloc_dbr(u16 size)
> >  		return DBR_SIZE; /* out of memory */
> > 
> >  	for (i = 0; i < DBR_MAP_SIZE; i++) {
> > -		u32 const blocks = (size + DBR_BLOCK_SIZE - 1) / DBR_BLOCK_SIZE;
> > +		u32 const blocks = DIV_ROUND_UP(size, DBR_BLOCK_SIZE);
> >  		u32 mask = ~((~(u32)0) << blocks);
> 
> Totally unrelated to DIV_ROUND_UP, would this code be a candidate for
> GENMASK?

Maybe "(1 << blocks) - 1" would be more intelligible.

Re: [Outreachy kernel] [PATCH v2 2/7] staging: most: Using macro DIV_ROUND_UP

[Julia Lawall]

[-- Attachment #1: Type: text/plain, Size: 2945 bytes --]



On Wed, 22 Feb 2017, SIMRAN SINGHAL wrote:

>
>
> On Wednesday, February 22, 2017 at 2:57:17 PM UTC+5:30, Julia Lawall wrote:
>       > @@ -117,7 +118,7 @@ static int alloc_dbr(u16 size)
>       >                  return DBR_SIZE; /* out of memory */
>       >
>       >          for (i = 0; i < DBR_MAP_SIZE; i++) {
>       > -                u32 const blocks = (size + DBR_BLOCK_SIZE -
>       1) / DBR_BLOCK_SIZE;
>       > +                u32 const blocks = DIV_ROUND_UP(size,
>       DBR_BLOCK_SIZE);
>       >                  u32 mask = ~((~(u32)0) << blocks);
>
>       Totally unrelated to DIV_ROUND_UP, would this code be a
>       candidate for
>       GENMASK?
>
>  
>       Not sure, what you are trying to say.

There was a discussion on the list recently about GENMASK, which allows to
create a mask containing a sequence of 1s, like 000011110000.  It looks
like that is what is being done here, because ~0 is 11111111 and then it
ie being shifted left and all the bits inverted.  But Joe had another
suggestion.  One could double check that his suggestion gives the right
result.

julia

>
>  
>
>       julia
>
>       >
>       >                  do {
>       > @@ -137,7 +138,7 @@ static int alloc_dbr(u16 size)
>       >  static void free_dbr(int offs, int size)
>       >  {
>       >          int block_idx = offs / DBR_BLOCK_SIZE;
>       > -        u32 const blocks = (size + DBR_BLOCK_SIZE - 1) /
>       DBR_BLOCK_SIZE;
>       > +        u32 const blocks = DIV_ROUND_UP(size,
>       DBR_BLOCK_SIZE);
>       >          u32 mask = ~((~(u32)0) << blocks);
>       >
>       >          mask <<= block_idx % 32;
>       > --
>       > 2.7.4
>       >
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