zd1211rw: use stack and preallocated memory for small cmd-buffers

Use stack for allocing small < 64 byte arrays in zd_chip.c and preallocated
buffer in zd_usb.c. This might lower CPU usage for beacon setup.

v2:
 - Do not use stack buffers in zd_usb.c as they would be used for urb
   transfer_buffer.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@mbnet.fi>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

3 files changed, 41 insertions, 44 deletions

diff --git a/drivers/net/wireless/zd1211rw/zd_chip.c b/drivers/net/wireless/zd1211rw/zd_chip.c
index d8dc92711f40..907e6562cb59 100644
--- a/drivers/net/wireless/zd1211rw/zd_chip.c
+++ b/drivers/net/wireless/zd1211rw/zd_chip.c
@@ -108,25 +108,17 @@ int zd_ioread32v_locked(struct zd_chip *chip, u32 *values, const zd_addr_t *addr
 {
         int r;
         int i;
-        zd_addr_t *a16;
-        u16 *v16;
+        zd_addr_t a16[USB_MAX_IOREAD32_COUNT * 2];
+        u16 v16[USB_MAX_IOREAD32_COUNT * 2];
         unsigned int count16;
 
         if (count > USB_MAX_IOREAD32_COUNT)
                 return -EINVAL;
 
-        /* Allocate a single memory block for values and addresses. */
-        count16 = 2*count;
-        /* zd_addr_t is __nocast, so the kmalloc needs an explicit cast */
-        a16 = (zd_addr_t *) kmalloc(count16 * (sizeof(zd_addr_t) + sizeof(u16)),
-                                   GFP_KERNEL);
-        if (!a16) {
-                dev_dbg_f(zd_chip_dev(chip),
-                          "error ENOMEM in allocation of a16\n");
-                r = -ENOMEM;
-                goto out;
-        }
-        v16 = (u16 *)(a16 + count16);
+        /* Use stack for values and addresses. */
+        count16 = 2 * count;
+        BUG_ON(count16 * sizeof(zd_addr_t) > sizeof(a16));
+        BUG_ON(count16 * sizeof(u16) > sizeof(v16));
 
         for (i = 0; i < count; i++) {
                 int j = 2*i;
@@ -139,7 +131,7 @@ int zd_ioread32v_locked(struct zd_chip *chip, u32 *values, const zd_addr_t *addr
         if (r) {
                 dev_dbg_f(zd_chip_dev(chip),
                           "error: zd_ioread16v_locked. Error number %d\n", r);
-                goto out;
+                return r;
         }
 
         for (i = 0; i < count; i++) {
@@ -147,18 +139,18 @@ int zd_ioread32v_locked(struct zd_chip *chip, u32 *values, const zd_addr_t *addr
                 values[i] = (v16[j] << 16) | v16[j+1];
         }
 
-out:
-        kfree((void *)a16);
-        return r;
+        return 0;
 }
 
 int _zd_iowrite32v_locked(struct zd_chip *chip, const struct zd_ioreq32 *ioreqs,
                    unsigned int count)
 {
         int i, j, r;
-        struct zd_ioreq16 *ioreqs16;
+        struct zd_ioreq16 ioreqs16[USB_MAX_IOWRITE32_COUNT * 2];
         unsigned int count16;
 
+        /* Use stack for values and addresses. */
+
         ZD_ASSERT(mutex_is_locked(&chip->mutex));
 
         if (count == 0)
@@ -166,15 +158,8 @@ int _zd_iowrite32v_locked(struct zd_chip *chip, const struct zd_ioreq32 *ioreqs,
         if (count > USB_MAX_IOWRITE32_COUNT)
                 return -EINVAL;
 
-        /* Allocate a single memory block for values and addresses. */
-        count16 = 2*count;
-        ioreqs16 = kmalloc(count16 * sizeof(struct zd_ioreq16), GFP_KERNEL);
-        if (!ioreqs16) {
-                r = -ENOMEM;
-                dev_dbg_f(zd_chip_dev(chip),
-                          "error %d in ioreqs16 allocation\n", r);
-                goto out;
-        }
+        count16 = 2 * count;
+        BUG_ON(count16 * sizeof(struct zd_ioreq16) > sizeof(ioreqs16));
 
         for (i = 0; i < count; i++) {
                 j = 2*i;
@@ -192,8 +177,6 @@ int _zd_iowrite32v_locked(struct zd_chip *chip, const struct zd_ioreq32 *ioreqs,
                           "error %d in zd_usb_write16v\n", r);
         }
 #endif /* DEBUG */
-out:
-        kfree(ioreqs16);
         return r;
 }
 
diff --git a/drivers/net/wireless/zd1211rw/zd_usb.c b/drivers/net/wireless/zd1211rw/zd_usb.c
index 9493ab86a41e..bf1de04dc9f2 100644
--- a/drivers/net/wireless/zd1211rw/zd_usb.c
+++ b/drivers/net/wireless/zd1211rw/zd_usb.c
@@ -1361,15 +1361,20 @@ int zd_usb_ioread16v(struct zd_usb *usb, u16 *values,
                 return -EWOULDBLOCK;
         }
         if (!usb_int_enabled(usb)) {
-                 dev_dbg_f(zd_usb_dev(usb),
+                dev_dbg_f(zd_usb_dev(usb),
                           "error: usb interrupt not enabled\n");
                 return -EWOULDBLOCK;
         }
 
+        ZD_ASSERT(mutex_is_locked(&zd_usb_to_chip(usb)->mutex));
+        BUILD_BUG_ON(sizeof(struct usb_req_read_regs) + USB_MAX_IOREAD16_COUNT *
+                     sizeof(__le16) > sizeof(usb->req_buf));
+        BUG_ON(sizeof(struct usb_req_read_regs) + count * sizeof(__le16) >
+               sizeof(usb->req_buf));
+
         req_len = sizeof(struct usb_req_read_regs) + count * sizeof(__le16);
-        req = kmalloc(req_len, GFP_KERNEL);
-        if (!req)
-                return -ENOMEM;
+        req = (void *)usb->req_buf;
+
         req->id = cpu_to_le16(USB_REQ_READ_REGS);
         for (i = 0; i < count; i++)
                 req->addr[i] = cpu_to_le16((u16)addresses[i]);
@@ -1402,7 +1407,6 @@ int zd_usb_ioread16v(struct zd_usb *usb, u16 *values,
 
         r = get_results(usb, values, req, count);
 error:
-        kfree(req);
         return r;
 }
 
@@ -1428,11 +1432,17 @@ int zd_usb_iowrite16v(struct zd_usb *usb, const struct zd_ioreq16 *ioreqs,
                 return -EWOULDBLOCK;
         }
 
+        ZD_ASSERT(mutex_is_locked(&zd_usb_to_chip(usb)->mutex));
+        BUILD_BUG_ON(sizeof(struct usb_req_write_regs) +
+                     USB_MAX_IOWRITE16_COUNT * sizeof(struct reg_data) >
+                     sizeof(usb->req_buf));
+        BUG_ON(sizeof(struct usb_req_write_regs) +
+               count * sizeof(struct reg_data) >
+               sizeof(usb->req_buf));
+
         req_len = sizeof(struct usb_req_write_regs) +
                   count * sizeof(struct reg_data);
-        req = kmalloc(req_len, GFP_KERNEL);
-        if (!req)
-                return -ENOMEM;
+        req = (void *)usb->req_buf;
 
         req->id = cpu_to_le16(USB_REQ_WRITE_REGS);
         for (i = 0; i < count; i++) {
@@ -1460,7 +1470,6 @@ int zd_usb_iowrite16v(struct zd_usb *usb, const struct zd_ioreq16 *ioreqs,
 
         /* FALL-THROUGH with r == 0 */
 error:
-        kfree(req);
         return r;
 }
 
@@ -1505,14 +1514,19 @@ int zd_usb_rfwrite(struct zd_usb *usb, u32 value, u8 bits)
         if (r) {
                 dev_dbg_f(zd_usb_dev(usb),
                         "error %d: Couldn't read CR203\n", r);
-                goto out;
+                return r;
         }
         bit_value_template &= ~(RF_IF_LE|RF_CLK|RF_DATA);
 
+        ZD_ASSERT(mutex_is_locked(&zd_usb_to_chip(usb)->mutex));
+        BUILD_BUG_ON(sizeof(struct usb_req_rfwrite) +
+                     USB_MAX_RFWRITE_BIT_COUNT * sizeof(__le16) >
+                     sizeof(usb->req_buf));
+        BUG_ON(sizeof(struct usb_req_rfwrite) + bits * sizeof(__le16) >
+               sizeof(usb->req_buf));
+
         req_len = sizeof(struct usb_req_rfwrite) + bits * sizeof(__le16);
-        req = kmalloc(req_len, GFP_KERNEL);
-        if (!req)
-                return -ENOMEM;
+        req = (void *)usb->req_buf;
 
         req->id = cpu_to_le16(USB_REQ_WRITE_RF);
         /* 1: 3683a, but not used in ZYDAS driver */
@@ -1544,6 +1558,5 @@ int zd_usb_rfwrite(struct zd_usb *usb, u32 value, u8 bits)
 
         /* FALL-THROUGH with r == 0 */
 out:
-        kfree(req);
         return r;
 }
diff --git a/drivers/net/wireless/zd1211rw/zd_usb.h b/drivers/net/wireless/zd1211rw/zd_usb.h
index 233ce825b71c..2ed48ae3e604 100644
--- a/drivers/net/wireless/zd1211rw/zd_usb.h
+++ b/drivers/net/wireless/zd1211rw/zd_usb.h
@@ -207,6 +207,7 @@ struct zd_usb {
         struct zd_usb_rx rx;
         struct zd_usb_tx tx;
         struct usb_interface *intf;
+        u8 req_buf[64]; /* zd_usb_iowrite16v needs 62 bytes */
         u8 is_zd1211b:1, initialized:1;
 };