linux-kernel - [PATCH] media: stkwebcam: move stk_camera_read_reg() scratch buffer to struct stk

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Date:   Sat, 12 Mar 2022 09:30:49 -0800
From:   trix@...hat.com
To:     mchehab@...nel.org, hverkuil-cisco@...all.nl,
        cai.huoqing@...ux.dev, paskripkin@...il.com, xose.vazquez@...il.com
Cc:     linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tom Rix <trix@...hat.com>
Subject: [PATCH] media: stkwebcam: move stk_camera_read_reg() scratch buffer to struct stk_camera

From: Tom Rix <trix@...hat.com>

In stk_camera_read_reg() a single byte buffer is alloc-ed and
freed on every function call.  Since the size is known,
move the buffer to the struct stk_camera where it will be alloc-ed
and freed once.

Signed-off-by: Tom Rix <trix@...hat.com>
---
 drivers/media/usb/stkwebcam/stk-webcam.c | 11 ++---------
 drivers/media/usb/stkwebcam/stk-webcam.h |  2 ++
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/drivers/media/usb/stkwebcam/stk-webcam.c b/drivers/media/usb/stkwebcam/stk-webcam.c
index 5b822214ccc5c..787edb3d47c23 100644
--- a/drivers/media/usb/stkwebcam/stk-webcam.c
+++ b/drivers/media/usb/stkwebcam/stk-webcam.c
@@ -150,25 +150,18 @@ int stk_camera_write_reg(struct stk_camera *dev, u16 index, u8 value)
 int stk_camera_read_reg(struct stk_camera *dev, u16 index, u8 *value)
 {
 	struct usb_device *udev = dev->udev;
-	unsigned char *buf;
 	int ret;
 
-	buf = kmalloc(sizeof(u8), GFP_KERNEL);
-	if (!buf)
-		return -ENOMEM;
-
 	ret = usb_control_msg(udev, usb_rcvctrlpipe(udev, 0),
 			0x00,
 			USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_DEVICE,
 			0x00,
 			index,
-			buf,
+			&dev->read_reg_scratch,
 			sizeof(u8),
 			500);
 	if (ret >= 0)
-		*value = *buf;
-
-	kfree(buf);
+		*value = dev->read_reg_scratch;
 
 	if (ret < 0)
 		return ret;
diff --git a/drivers/media/usb/stkwebcam/stk-webcam.h b/drivers/media/usb/stkwebcam/stk-webcam.h
index 14519e5308b18..136decffe9ced 100644
--- a/drivers/media/usb/stkwebcam/stk-webcam.h
+++ b/drivers/media/usb/stkwebcam/stk-webcam.h
@@ -105,6 +105,8 @@ struct stk_camera {
 	struct list_head sio_avail;
 	struct list_head sio_full;
 	unsigned sequence;
+
+	u8 read_reg_scratch;
 };
 
 #define vdev_to_camera(d) container_of(d, struct stk_camera, vdev)
-- 
2.26.3