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SubjectRe: [PATCH] drivers: rtl818x: request DMA-able memory
On Mon, Oct 25, 2010 at 03:11:22PM +0100, Hin-Tak Leung wrote:
>
>
> Larry Finger wrote:
> >On 10/24/2010 03:32 PM, 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@debian.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;
> >
> >ACK.
> >
> >Larry
>
> Acked-by: Hin-Tak Leung <htl10@users.sourceforge.net>
>
> I had a quick look for similiar constructs and AFAIK only the
> b43/b43legacy drivers uses DMA buffers. Seems to be a rare practice.
> Is that something we should or should not do?

It doesn't mean what you think it means. It is a relic of the past,
used to indicate memory below 16MB so that ISA devices could do DMA.

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


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