Re: [RFT] rtl8187: use DMA-aware buffers with usb_control_msg

[Greg KH <greg@kroah.com>]

On Sat, May 09, 2009 at 11:38:32AM +0200, Eric Valette wrote:
> The patch fix the DMA warning and the driver seems to work (just
> associated it) but I must say that the allocation failure handling path
> and the fact that we use now kmalloc for allocating a few bytes in such
> a routine makes me worry about possible negative performance impact
> unless theses routines are used only in a slow configuration path (did
> no took time to red the code due to many other problems).

usb_control messages are slow and should not be on the "fast path" of
any data being sent through the device.  Any overhead of the
kmalloc/kfree is totally eaten up by the actual transmission turn around
time of the message itself, so you don't have to worry about the
performance impact.

thanks for testing.

> BTW if someone know who I should send this attached patch for DRM git, I
> would gladly forward it.

To the drm maintainer?

thanks,

greg k-h