linux-kernel - Re: cx23885-input.c does in fact use a workqueue....

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Message-ID: <20110214110339.GC18742@htj.dyndns.org>
Date:	Mon, 14 Feb 2011 12:03:39 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Dmitry Torokhov <dmitry.torokhov@...il.com>
Cc:	Andy Walls <awalls@...metrocast.net>, linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org, stoth@...nellabs.com
Subject: Re: cx23885-input.c does in fact use a workqueue....

Hello,

On Sun, Feb 13, 2011 at 08:33:55PM -0800, Dmitry Torokhov wrote:
> > The cx23885 driver does in fact schedule work for IR input handling:
> > 
> > Here's where it is scheduled for CX23888 chips:
> > 
> > http://git.linuxtv.org/media_tree.git?a=blob;f=drivers/media/video/cx23885/cx23885-ir.c;h=7125247dd25558678c823ee3262675570c9aa630;hb=HEAD#l76
> > 
> > Here's where it is scheduled for CX23885 chips:
> > 
> > http://git.linuxtv.org/media_tree.git?a=blob;f=drivers/media/video/cx23885/cx23885-core.c;h=359882419b7f588b7c698dbcfb6a39ddb1603301;hb=HEAD#l1861

Ah, sorry about missing those.

> > The two different chips are handled slightly differently because
> > 
> > a. the CX23888 IR unit is accessable via a PCI register block.  The IR
> > IRQ can be acknowledged with direct PCI register accesses in an
> > interrupt context, and the IR pulse FIFO serviced later in a workqueue
> > context.
> > 
> > b. the CX23885 IR unit is accessed over an I2C bus.  The CX23885 A/V IRQ
> > has to be masked in an interrupt context (with PCI registers accesses).
> > Then the CX23885 A/V unit's IR IRQ is ack'ed over I2C in a workqueue
> > context and the IR pulse FIFO is also serviced over I2C in a workqueue
> > context.
> > 
> > 
> > So what should be done about the flush_scheduled_work()?  I think it
> > belongs there.
> > 
> 
> Convert to using threaded irq?

Or

1. Just flush the work items explicitly using flush_work_sync().

2. Create a dedicated workqueue to serve as flushing domain.

The first would look like the following.  Does this look correct?

Thanks.

diff --git a/drivers/media/video/cx23885/cx23885-input.c b/drivers/media/video/cx23885/cx23885-input.c
index 199b996..e27cedb 100644
--- a/drivers/media/video/cx23885/cx23885-input.c
+++ b/drivers/media/video/cx23885/cx23885-input.c
@@ -229,6 +229,9 @@ static void cx23885_input_ir_stop(struct cx23885_dev *dev)
 		v4l2_subdev_call(dev->sd_ir, ir, rx_s_parameters, &params);
 		v4l2_subdev_call(dev->sd_ir, ir, rx_g_parameters, &params);
 	}
+	flush_work_sync(&dev->cx25840_work);
+	flush_work_sync(&dev->ir_rx_work);
+	flush_work_sync(&dev->ir_tx_work);
 }
 
 static void cx23885_input_ir_close(struct rc_dev *rc)

-- 
tejun
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