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Subject[PATCH 5/6] drivers/atm: Use DIV_ROUND_UP
In each case below, I have followed the original semantics, but in
drivers/atm/eni.c and drivers/atm/horizon.c, I have some doubts as to
whether the original semantics is correct. In drivers/atm/eni.c, is the
division intended to be by div or by div-1? In drivers/atm/horizon.c, it
seems strange that "case round_down" is implemented by DIV_ROUND_UP, twice.
The round_down and default (ie round_up) cases seem to be inversed.

---
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>

---
diff -u -p a/drivers/atm/eni.c b/drivers/atm/eni.c
--- a/drivers/atm/eni.c 2007-07-20 15:28:28.000000000 +0200
+++ b/drivers/atm/eni.c 2008-02-13 20:50:10.000000000 +0100
@@ -1270,7 +1270,7 @@ static int comp_tx(struct eni_dev *eni_d
if (*pre < 3) (*pre)++; /* else fail later */
div = pre_div[*pre]*-*pcr;
DPRINTK("max div %d\n",div);
- *res = (TS_CLOCK+div-1)/div-1;
+ *res = DIV_ROUND_UP(TS_CLOCK, div)-1;
}
if (*res < 0) *res = 0;
if (*res > MID_SEG_MAX_RATE) *res = MID_SEG_MAX_RATE;
diff -u -p a/drivers/atm/horizon.c b/drivers/atm/horizon.c
--- a/drivers/atm/horizon.c 2007-11-08 18:33:26.000000000 +0100
+++ b/drivers/atm/horizon.c 2008-02-13 20:50:13.000000000 +0100
@@ -635,7 +635,7 @@ static int make_rate (const hrz_dev * de
// take care of rounding
switch (r) {
case round_down:
- pre = (br+(c<<div)-1)/(c<<div);
+ pre = DIV_ROUND_UP(br, c<<div);
// but p must be non-zero
if (!pre)
pre = 1;
@@ -668,7 +668,7 @@ static int make_rate (const hrz_dev * de
// take care of rounding
switch (r) {
case round_down:
- pre = (br+(c<<div)-1)/(c<<div);
+ pre = DIV_ROUND_UP(br, c<<div);
break;
case round_nearest:
pre = (br+(c<<div)/2)/(c<<div);
@@ -698,7 +698,7 @@ got_it:
if (bits)
*bits = (div<<CLOCK_SELECT_SHIFT) | (pre-1);
if (actual) {
- *actual = (br + (pre<<div) - 1) / (pre<<div);
+ *actual = DIV_ROUND_UP(br, pre<<div);
PRINTD (DBG_QOS, "actual rate: %u", *actual);
}
return 0;
@@ -1967,7 +1967,7 @@ static int __devinit hrz_init (hrz_dev *
// Set the max AAL5 cell count to be just enough to contain the
// largest AAL5 frame that the user wants to receive
wr_regw (dev, MAX_AAL5_CELL_COUNT_OFF,
- (max_rx_size + ATM_AAL5_TRAILER + ATM_CELL_PAYLOAD - 1) / ATM_CELL_PAYLOAD);
+ DIV_ROUND_UP(max_rx_size + ATM_AAL5_TRAILER, ATM_CELL_PAYLOAD));

// Enable receive
wr_regw (dev, RX_CONFIG_OFF, rd_regw (dev, RX_CONFIG_OFF) | RX_ENABLE);
diff -u -p a/drivers/atm/zatm.c b/drivers/atm/zatm.c
--- a/drivers/atm/zatm.c 2007-07-20 15:28:28.000000000 +0200
+++ b/drivers/atm/zatm.c 2008-02-14 07:26:36.000000000 +0100
@@ -496,8 +496,8 @@ static int open_rx_first(struct atm_vcc
vcc->qos.rxtp.max_sdu = 65464;
/* fix this - we may want to receive 64kB SDUs
later */
- cells = (vcc->qos.rxtp.max_sdu+ATM_AAL5_TRAILER+
- ATM_CELL_PAYLOAD-1)/ATM_CELL_PAYLOAD;
+ cells = DIV_ROUND_UP(vcc->qos.rxtp.max_sdu+ATM_AAL5_TRAILER,
+ ATM_CELL_PAYLOAD);
zatm_vcc->pool = pool_index(cells*ATM_CELL_PAYLOAD);
}
else {
@@ -820,7 +820,7 @@ static int alloc_shaper(struct atm_dev *
}
else {
i = 255;
- m = (ATM_OC3_PCR*255+max-1)/max;
+ m = DIV_ROUND_UP(ATM_OC3_PCR*255, max);
}
}
if (i > m) {

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