linux-kernel - [PATCH 2/3] sound: usb: line6: Replace mdelay with msleep in line6_write

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Date:   Sun, 18 Mar 2018 22:51:59 +0800
From:   Jia-Ju Bai <baijiaju1990@...il.com>
To:     perex@...ex.cz, tiwai@...e.com
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        Jia-Ju Bai <baijiaju1990@...il.com>
Subject: [PATCH 2/3] sound: usb: line6: Replace mdelay with msleep in line6_write_data

line6_write_data() is never called in atomic context.

The call chains ending up at line6_write_data() are:
[1] line6_write_data() <- toneport_setup() <- toneport_init() 
	<- line6_probe()
[2] line6_write_data() <- toneport_setup() <- toneport_reset_resume()

line6_probe() is called in toneport_probe(), pod_probe(), podhd_probe() 
and variax_probe(), which are set as ".probe" in usb_driver structure.
toneport_reset_resume() is set as ".reset_resume" in usb_driver structure.
These functions are not called in atomic context.

Despite never getting called from atomic context, line6_write_data()
calls mdelay for busy wait.
That is not necessary and can be replaced with msleep to 
avoid busy waiting.

This is found by a static analysis tool named DCNS written by myself.

Signed-off-by: Jia-Ju Bai <baijiaju1990@...il.com>
---
 sound/usb/line6/driver.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/usb/line6/driver.c b/sound/usb/line6/driver.c
index 0ff5a7d..29acd86 100644
--- a/sound/usb/line6/driver.c
+++ b/sound/usb/line6/driver.c
@@ -426,7 +426,7 @@ int line6_write_data(struct usb_line6 *line6, unsigned address, void *data,
 	}

 	for (count = 0; count < LINE6_READ_WRITE_MAX_RETRIES; count++) {
-		mdelay(LINE6_READ_WRITE_STATUS_DELAY);
+		msleep(LINE6_READ_WRITE_STATUS_DELAY);

 		ret = usb_control_msg(usbdev, usb_rcvctrlpipe(usbdev, 0),
 				      0x67,
-- 
1.9.1