Subject: Re: [v4l-dvb-maintainer] [PATCH] cafe_ccic: default to allocating
	DMA buffers at probe time
From: Mauro Carvalho Chehab <mchehab@infradead.org>
To: Andres Salomon <dilinger@queued.net>
Cc: video4linux-list@redhat.com, linux-kernel@vger.kernel.org,
       v4l-dvb-maintainer@linuxtv.org, akpm@linux-foundation.org,
       corbet@lwn.net
In-Reply-To: <20070919014418.073543bc.dilinger@queued.net>
References: <20070919014418.073543bc.dilinger@queued.net>
Content-Type: text/plain; charset=utf-8
Date: Mon, 24 Sep 2007 12:04:17 -0300
Message-Id: <1190646257.8360.65.camel@gaivota>
Mime-Version: 1.0
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Sender: linux-kernel-owner@vger.kernel.org
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Hi Andres,

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

Cheers,
Mauro.

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@linuxtv.org
> http://www.linuxtv.org/cgi-bin/mailman/listinfo/v4l-dvb-maintainer
-- 
Cheers,
Mauro

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