V4L/DVB (9646): em28xx: avoid allocating/dealocating memory on every control urb

Before this patch, every register setup on em28xx were dynamically
allocating a temporary buffer for control URB's to be handled.

To avoid this ping-pong, use, instead a pre-allocated buffer.

Also, be sure that read control URB's also use the buffer, instead of
relying on a stack buffer.

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

2 files changed, 31 insertions, 22 deletions

diff --git a/drivers/media/video/em28xx/em28xx-core.c b/drivers/media/video/em28xx/em28xx-core.c
index 038da614a734..9551b8ab8c44 100644
--- a/drivers/media/video/em28xx/em28xx-core.c
+++ b/drivers/media/video/em28xx/em28xx-core.c
@@ -69,19 +69,29 @@ int em28xx_read_reg_req_len(struct em28xx *dev, u8 req, u16 reg,
         int ret, byte;
 
         if (dev->state & DEV_DISCONNECTED)
-                return(-ENODEV);
+                return -ENODEV;
+
+        if (len > URB_MAX_CTRL_SIZE)
+                return -EINVAL;
 
         em28xx_regdbg("req=%02x, reg=%02x ", req, reg);
 
         ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0), req,
                               USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-                              0x0000, reg, buf, len, HZ);
+                              0x0000, reg, dev->urb_buf, len, HZ);
+        if (ret < 0) {
+                if (reg_debug)
+                        printk(" failed!\n");
+                return ret;
+        }
+
+        if (len)
+                memcpy(buf, dev->urb_buf, len);
 
         if (reg_debug) {
-                printk(ret < 0 ? " failed!\n" : "%02x values: ", ret);
+                printk("%02x values: ", ret);
                 for (byte = 0; byte < len; byte++)
                         printk(" %02x", (unsigned char)buf[byte]);
-
                 printk("\n");
         }
 
@@ -104,14 +114,16 @@ int em28xx_read_reg_req(struct em28xx *dev, u8 req, u16 reg)
 
         ret = usb_control_msg(dev->udev, usb_rcvctrlpipe(dev->udev, 0), req,
                               USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-                              0x0000, reg, &val, 1, HZ);
+                              0x0000, reg, dev->urb_buf, 1, HZ);
+        if (ret < 0) {
+                printk(" failed!\n");
+                return ret;
+        }
 
-        if (reg_debug)
-                printk(ret < 0 ? " failed!\n" :
-                                 "%02x\n", (unsigned char) val);
+        val = dev->urb_buf[0];
 
-        if (ret < 0)
-                return ret;
+        if (reg_debug)
+                printk("%02x\n", (unsigned char) val);
 
         return val;
 }
@@ -130,19 +142,13 @@ int em28xx_write_regs_req(struct em28xx *dev, u8 req, u16 reg, char *buf,
 {
         int ret;
 
-        /*usb_control_msg seems to expect a kmalloced buffer */
-        unsigned char *bufs;
-
         if (dev->state & DEV_DISCONNECTED)
                 return -ENODEV;
 
-        if (len < 1)
+        if ((len < 1) || (len > URB_MAX_CTRL_SIZE))
                 return -EINVAL;
 
-        bufs = kmalloc(len, GFP_KERNEL);
-
         em28xx_regdbg("req=%02x reg=%02x:", req, reg);
-
         if (reg_debug) {
                 int i;
                 for (i = 0; i < len; ++i)
@@ -150,16 +156,14 @@ int em28xx_write_regs_req(struct em28xx *dev, u8 req, u16 reg, char *buf,
                 printk("\n");
         }
 
-        if (!bufs)
-                return -ENOMEM;
-        memcpy(bufs, buf, len);
+        memcpy(dev->urb_buf, buf, len);
         ret = usb_control_msg(dev->udev, usb_sndctrlpipe(dev->udev, 0), req,
                               USB_DIR_OUT | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
-                              0x0000, reg, bufs, len, HZ);
+                              0x0000, reg, dev->urb_buf, len, HZ);
+
         if (dev->wait_after_write)
                 msleep(dev->wait_after_write);
 
-        kfree(bufs);
         return ret;
 }
 
diff --git a/drivers/media/video/em28xx/em28xx.h b/drivers/media/video/em28xx/em28xx.h
index 82781178e0a3..1adf3d9d9bff 100644
--- a/drivers/media/video/em28xx/em28xx.h
+++ b/drivers/media/video/em28xx/em28xx.h
@@ -102,6 +102,9 @@
 #define EM28XX_MIN_BUF 4
 #define EM28XX_DEF_BUF 8
 
+/*Limits the max URB message size */
+#define URB_MAX_CTRL_SIZE 80
+
 /* Params for validated field */
 #define EM28XX_BOARD_NOT_VALIDATED 1
 #define EM28XX_BOARD_VALIDATED     0
@@ -451,6 +454,8 @@ struct em28xx {
         unsigned int *alt_max_pkt_size; /* array of wMaxPacketSize */
         struct urb *urb[EM28XX_NUM_BUFS];       /* urb for isoc transfers */
         char *transfer_buffer[EM28XX_NUM_BUFS]; /* transfer buffers for isoc transfer */
+        char urb_buf[URB_MAX_CTRL_SIZE];        /* urb control msg buffer */
+
         /* helper funcs that call usb_control_msg */
         int (*em28xx_write_regs) (struct em28xx *dev, u16 reg,
                                         char *buf, int len);