linux-kernel - Re: [v4l-dvb-maintainer] [PATCH] cafe_ccic: default to allocating DMA buffers at probe time

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Date:	Tue, 25 Sep 2007 02:02:45 -0400
From:	Andres Salomon <dilinger@...ued.net>
To:	Mauro Carvalho Chehab <mchehab@...radead.org>
Cc:	video4linux-list@...hat.com, linux-kernel@...r.kernel.org,
	v4l-dvb-maintainer@...uxtv.org, akpm@...ux-foundation.org,
	corbet@....net
Subject: Re: [v4l-dvb-maintainer] [PATCH] cafe_ccic: default to allocating
 DMA buffers at probe time

On Mon, 24 Sep 2007 12:04:17 -0300
Mauro Carvalho Chehab <mchehab@...radead.org> wrote:

> Hi Andres,
> 
> Still missing on your patch is your SOB ;) From what I got from Jon, he
> is ok with your patch.
> 
> Cheers,
> Mauro.

Whoops, sorry about that!   well, here it is (for the patch below):

Signed-off-by: Andres Salomon <dilinger@...ian.org>

> 
> Em Qua, 2007-09-19 às 01:44 -0400, Andres Salomon escreveu:
> > By default, we allocate DMA buffers when actually reading from the video
> > capture device.  On a system with 128MB or 256MB of ram, it's very easy
> > for that memory to quickly become fragmented.  We've had users report
> > having 30+MB of memory free, but the cafe_ccic driver is still unable to
> > allocate DMA buffers.
> > 
> > Our workaround has been to make use of the 'alloc_bufs_at_load' parameter
> > to allocate DMA buffers during device probing.  This patch makes DMA
> > buffer allocation happen during device probe by default, and changes
> > the parameter to 'alloc_bufs_at_read'.  The camera hardware is there,
> > if the cafe_ccic driver is enabled/loaded it should do its best to ensure
> > that the camera is actually usable; delaying DMA buffer allocation
> > saves an insignicant amount of memory, and causes the driver to be much
> > less useful.
> > ---
> > 
> >  drivers/media/video/cafe_ccic.c |   18 +++++++++---------
> >  1 files changed, 9 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/media/video/cafe_ccic.c b/drivers/media/video/cafe_ccic.c
> > index ef53618..3588a59 100644
> > --- a/drivers/media/video/cafe_ccic.c
> > +++ b/drivers/media/video/cafe_ccic.c
> > @@ -63,13 +63,13 @@ MODULE_SUPPORTED_DEVICE("Video");
> >   */
> >  
> >  #define MAX_DMA_BUFS 3
> > -static int alloc_bufs_at_load = 0;
> > -module_param(alloc_bufs_at_load, bool, 0444);
> > -MODULE_PARM_DESC(alloc_bufs_at_load,
> > -		"Non-zero value causes DMA buffers to be allocated at module "
> > -		"load time.  This increases the chances of successfully getting "
> > -		"those buffers, but at the cost of nailing down the memory from "
> > -		"the outset.");
> > +static int alloc_bufs_at_read = 0;
> > +module_param(alloc_bufs_at_read, bool, 0444);
> > +MODULE_PARM_DESC(alloc_bufs_at_read,
> > +		"Non-zero value causes DMA buffers to be allocated when the "
> > +		"video capture device is read, rather than at module load "
> > +		"time.  This saves memory, but decreases the chances of "
> > +		"successfully getting those buffers.");
> >  
> >  static int n_dma_bufs = 3;
> >  module_param(n_dma_bufs, uint, 0644);
> > @@ -1503,7 +1503,7 @@ static int cafe_v4l_release(struct inode *inode, struct file *filp)
> >  	}
> >  	if (cam->users == 0) {
> >  		cafe_ctlr_power_down(cam);
> > -		if (! alloc_bufs_at_load)
> > +		if (alloc_bufs_at_read)
> >  			cafe_free_dma_bufs(cam);
> >  	}
> >  	mutex_unlock(&cam->s_mutex);
> > @@ -2162,7 +2162,7 @@ static int cafe_pci_probe(struct pci_dev *pdev,
> >  	/*
> >  	 * If so requested, try to get our DMA buffers now.
> >  	 */
> > -	if (alloc_bufs_at_load) {
> > +	if (!alloc_bufs_at_read) {
> >  		if (cafe_alloc_dma_bufs(cam, 1))
> >  			cam_warn(cam, "Unable to alloc DMA buffers at load"
> >  					" will try again later.");
> > 
> > _______________________________________________
> > v4l-dvb-maintainer mailing list
> > v4l-dvb-maintainer@...uxtv.org
> > http://www.linuxtv.org/cgi-bin/mailman/listinfo/v4l-dvb-maintainer
> -- 
> Cheers,
> Mauro
> 

-- 
Andres Salomon <dilinger@...ued.net>
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