David Brownell wrote:
>
> I think I've got the answers to my questions now, and
> DaveM provided some info for DMA-mapping.txt
> to help make sure other folk get them too.
>
> For USB device drivers:
>
> - Buffers in URBs don't need to be aligned. This is
> for data transfer buffers, also control setup packets.
>
> - However the data buffers need to be allocated
> using __get_free_pages() or something using it
> (kmalloc, kmem_cache, skb_alloc, ...).
I lifted the following code from someones driver for the CATC driver.
#define ALIGN(x) x __attribute__((aligned(L1_CACHE_BYTES)))
__u8 ALIGN(tx_buf[USB_CATC_BUFF_SIZE]); /* outwards data
*/
__u8 ALIGN(rx_buf[USB_CATC_BUFF_SIZE]); /* inwards data */
Should that be sufficient?
Brad
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