linux-kernel - Re: [PATCH 3/3] [media] cx88: use a mutex to protect cx8802

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Date:	Mon, 4 Apr 2011 20:16:40 -0500
From:	Jonathan Nieder <jrnieder@...il.com>
To:	Andreas Huber <hobrom@....at>
Cc:	linux-media@...r.kernel.org, Huber Andreas <hobrom@...ax.at>,
	Mauro Carvalho Chehab <mchehab@...hat.com>,
	Hans Verkuil <hverkuil@...all.nl>,
	linux-kernel@...r.kernel.org, andrew.walker27@...world.com,
	Ben Hutchings <ben@...adent.org.uk>,
	Trent Piepho <xyzzy@...akeasy.org>,
	Roland Stoll <dvb.rs@...dex.de>
Subject: Re: [PATCH 3/3] [media] cx88: use a mutex to protect cx8802_devlist

Hi again,

Andreas Huber wrote:

> [...]
>     /* Make sure we can acquire the hardware */
>     drv = cx8802_get_driver(dev, CX88_MPEG_BLACKBIRD);      // HOW TO DEAL WITH NULL  ??????
>     if (drv) {

Reasonable question.  Could you try this patch?

-- 8< -- 
Subject: [media] cx88: lock device during driver initialization

Reported-by: Andreas Huber <hobrom@....at>
Signed-off-by: Jonathan Nieder <jrnieder@...il.com>
---
 drivers/media/video/cx88/cx88-blackbird.c |    2 --
 drivers/media/video/cx88/cx88-mpeg.c      |    5 ++---
 drivers/media/video/cx88/cx88.h           |    7 ++-----
 3 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/media/video/cx88/cx88-blackbird.c b/drivers/media/video/cx88/cx88-blackbird.c
index a6f7d53..f637d34 100644
--- a/drivers/media/video/cx88/cx88-blackbird.c
+++ b/drivers/media/video/cx88/cx88-blackbird.c
@@ -1335,11 +1335,9 @@ static int cx8802_blackbird_probe(struct cx8802_driver *drv)
 	blackbird_register_video(dev);
 
 	/* initial device configuration: needed ? */
-	mutex_lock(&dev->core->lock);
 //	init_controls(core);
 	cx88_set_tvnorm(core,core->tvnorm);
 	cx88_video_mux(core,0);
-	mutex_unlock(&dev->core->lock);
 
 	return 0;
 
diff --git a/drivers/media/video/cx88/cx88-mpeg.c b/drivers/media/video/cx88/cx88-mpeg.c
index 6b58647..b18f9fe 100644
--- a/drivers/media/video/cx88/cx88-mpeg.c
+++ b/drivers/media/video/cx88/cx88-mpeg.c
@@ -714,18 +714,17 @@ int cx8802_register_driver(struct cx8802_driver *drv)
 		drv->request_release = cx8802_request_release;
 		memcpy(driver, drv, sizeof(*driver));
 
+		mutex_lock(&drv->core->lock);
 		err = drv->probe(driver);
 		if (err == 0) {
 			i++;
-			mutex_lock(&drv->core->lock);
 			list_add_tail(&driver->drvlist, &dev->drvlist);
-			mutex_unlock(&drv->core->lock);
 		} else {
 			printk(KERN_ERR
 			       "%s/2: cx8802 probe failed, err = %d\n",
 			       dev->core->name, err);
 		}
-
+		mutex_unlock(&drv->core->lock);
 	}
 
 	err = i ? 0 : -ENODEV;
diff --git a/drivers/media/video/cx88/cx88.h b/drivers/media/video/cx88/cx88.h
index 9731daa..3d32f4a 100644
--- a/drivers/media/video/cx88/cx88.h
+++ b/drivers/media/video/cx88/cx88.h
@@ -505,13 +505,10 @@ struct cx8802_driver {
 	int (*suspend)(struct pci_dev *pci_dev, pm_message_t state);
 	int (*resume)(struct pci_dev *pci_dev);
 
+	/* Callers to the following functions must hold core->lock */
+
 	/* MPEG 8802 -> mini driver - Driver probe and configuration */
-
-	/* Caller must _not_ hold core->lock */
 	int (*probe)(struct cx8802_driver *drv);
-
-	/* Callers to the following functions must hold core->lock */
-
 	int (*remove)(struct cx8802_driver *drv);
 
 	/* MPEG 8802 -> mini driver - Access for hardware control */
-- 
1.7.5.rc0

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