linux-kernel - Re: [PATCH] drivers: rtl818x: request DMA-able memory

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Message-ID: <20101025133555.GB2414@tuxdriver.com>
Date:	Mon, 25 Oct 2010 09:35:56 -0400
From:	"John W. Linville" <linville@...driver.com>
To:	Serafeim Zanikolas <sez@...ian.org>
Cc:	herton@...driva.com.br, htl10@...rs.sourceforge.net,
	Larry.Finger@...inger.net, joe@...ches.com, davem@...emloft.net,
	linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drivers: rtl818x: request DMA-able memory

On Sun, Oct 24, 2010 at 10:32:07PM +0200, Serafeim Zanikolas wrote:
> Despite the indicated intention in comment, the kmalloc() call was not
> explicitly requesting memory from ZONE_DMA.
> 
> Signed-off-by: Serafeim Zanikolas <sez@...ian.org>
> ---
>  drivers/net/wireless/rtl818x/rtl8187_dev.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/net/wireless/rtl818x/rtl8187_dev.c b/drivers/net/wireless/rtl818x/rtl8187_dev.c
> index 38fa824..771794d 100644
> --- a/drivers/net/wireless/rtl818x/rtl8187_dev.c
> +++ b/drivers/net/wireless/rtl818x/rtl8187_dev.c
> @@ -1343,7 +1343,8 @@ static int __devinit rtl8187_probe(struct usb_interface *intf,
>  	priv->is_rtl8187b = (id->driver_info == DEVICE_RTL8187B);
>  
>  	/* allocate "DMA aware" buffer for register accesses */
> -	priv->io_dmabuf = kmalloc(sizeof(*priv->io_dmabuf), GFP_KERNEL);
> +	priv->io_dmabuf = kmalloc(sizeof(*priv->io_dmabuf),
> +				  GFP_DMA | GFP_KERNEL);
>  	if (!priv->io_dmabuf) {
>  		err = -ENOMEM;
>  		goto err_free_dev;

Are you sure about this?  Are there USB controllers out there with
the ISA 16MB limitation for DMA?

John
-- 
John W. Linville		Someday the world will need a hero, and you
linville@...driver.com			might be all we have.  Be ready.
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