Re: [PATCH] usb/mcs7830: Don't use buffers from stack for USB transfers

[Arnd Bergmann]

On Tuesday 20 January 2009, David Miller wrote:
> You cannot DMA from/to the kernel stack, because it might not be in
> the aliased linear mapping of physical memory.  It could even be
> vmalloc()'d memory on some platforms.

Ok, I see. It seems a bit of a waste to do a kmalloc for something
that is guaranteed to be just a few bytes, but allocating the
buffer per-device would mean another mutex, which has about the
same overhead, so I'm basically ok with the patch.

> +       buffer = kmalloc(size, GFP_NOIO);

GFP_NOIO seems out of place in a network driver: there is nothing
wrong with waiting for I/O here, so plain GFP_KERNEL should be fine.

> +       if (buffer == NULL)
> +               return -ENOMEM;

I'd prefer to write 

	if (!buffer)

here, as I do elsewhere in the driver.

Otherwise,

Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
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